Characterization of electrodes modified with nanocomposites of cobalt tetraaminophenoxyphthalocyanine, reduced graphene and multi-walled carbon nanotubes
- Shumba, Munyaradz, Nyoni, Stephen, Britton, Jonathan, Nyokong, Tebello
- Authors: Shumba, Munyaradz , Nyoni, Stephen , Britton, Jonathan , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187003 , vital:44555 , xlink:href="https://doi.org/10.1080/00958972.2019.1621299"
- Description: Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/ rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward L-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62x104 M-1 s-1 and a detection limit of 30 nM. The presence of rGONs improved the stability of the electrode.
- Full Text:
- Date Issued: 2019
- Authors: Shumba, Munyaradz , Nyoni, Stephen , Britton, Jonathan , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187003 , vital:44555 , xlink:href="https://doi.org/10.1080/00958972.2019.1621299"
- Description: Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/ rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward L-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62x104 M-1 s-1 and a detection limit of 30 nM. The presence of rGONs improved the stability of the electrode.
- Full Text:
- Date Issued: 2019
Chiral Modulation from Molecular to Macroscopic levels by synthetic chiral-amide-bonded porphyrin dimers
- Liang, Xu, Qin, Mingfeng, Zhang, Xiaomei, Mack, John, Soy, Rodah, Nyokong, Tebello, Zhu, Weihua
- Authors: Liang, Xu , Qin, Mingfeng , Zhang, Xiaomei , Mack, John , Soy, Rodah , Nyokong, Tebello , Zhu, Weihua
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186802 , vital:44535 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107637"
- Description: Six different nanoarchitectures were constructed by a series of synthetic bio-inspired chiral porphyrin dimers through molecular self-assembly behaviour. A plausible mechanism of chiral expression from the molecular to the macroscopic levels was investigated through an analysis of the optical spectroscopy and theoretical calculations.
- Full Text:
- Date Issued: 2019
- Authors: Liang, Xu , Qin, Mingfeng , Zhang, Xiaomei , Mack, John , Soy, Rodah , Nyokong, Tebello , Zhu, Weihua
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/186802 , vital:44535 , xlink:href="https://doi.org/10.1016/j.dyepig.2019.107637"
- Description: Six different nanoarchitectures were constructed by a series of synthetic bio-inspired chiral porphyrin dimers through molecular self-assembly behaviour. A plausible mechanism of chiral expression from the molecular to the macroscopic levels was investigated through an analysis of the optical spectroscopy and theoretical calculations.
- Full Text:
- Date Issued: 2019
Chlorophyll fluorometry as a method of determining the effectiveness of a biological control agent in post-release evaluations
- Miller, Benjamin E, Coetzee, Julie A, Hill, Martin P
- Authors: Miller, Benjamin E , Coetzee, Julie A , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417438 , vital:71453 , xlink:href="https://doi.org/10.1080/09583157.2019.1656165"
- Description: The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PIabs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.
- Full Text:
- Date Issued: 2019
- Authors: Miller, Benjamin E , Coetzee, Julie A , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/417438 , vital:71453 , xlink:href="https://doi.org/10.1080/09583157.2019.1656165"
- Description: The impact of the planthopper Megamelus scutellaris, a biocontrol agent of water hyacinth in South Africa, was assessed using chlorophyll fluorometry in a greenhouse study under two different eutrophic nutrient treatments and agent densities (high and low). The results indicated that plants grown in low nutrients with high densities of M. scutellaris showed the greatest reduction in the fluorescence parameters Fv/Fm and PIabs. The successful use of chlorophyll fluorometry for the detection of subtle insect damage to water hyacinth leaves could have future application in post-release studies to measure the impact of M. scutellaris in the field.
- Full Text:
- Date Issued: 2019
Co (ii) Tetraphenyltetraphenanthroporphyrin@ MWCNTs
- Gu, Tingting, Tao, Jaiyu, Zhu, Weihua, Mack, John, Soy, Rodah C, Nyokong, Tebello, Xu, Haijin, Li, Minzhi, Liang, Xu
- Authors: Gu, Tingting , Tao, Jaiyu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Xu, Haijin , Li, Minzhi , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234580 , vital:50210 , xlink:href="https://doi.org/10.1039/C9NJ01707K"
- Description: Herein, a cobalt(II)tetraphenyltetraphenanthroporphyrin (Co(II)TPTPP) with phenanthrene-fused pyrrole rings was synthesized and characterized. Moreover, a detailed analysis of its optical and redox properties was carried out by comparing the results obtained via optical spectroscopy and electrochemistry with the trends predicted via a series of DFT and TD-DFT calculations. The electrochemistry results demonstrated that the π-expanded Co(II)TPTPP interacted strongly with multiwall carbon nanotubes (MWCNTs), which were finally immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. This strong immobilization via π–π stacking between Co(II)TPTPP and MWCNTs leads to significantly stable electrochemically catalyzed hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), which provides a new insight into the understanding electron transfer channels.
- Full Text:
- Date Issued: 2019
- Authors: Gu, Tingting , Tao, Jaiyu , Zhu, Weihua , Mack, John , Soy, Rodah C , Nyokong, Tebello , Xu, Haijin , Li, Minzhi , Liang, Xu
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/234580 , vital:50210 , xlink:href="https://doi.org/10.1039/C9NJ01707K"
- Description: Herein, a cobalt(II)tetraphenyltetraphenanthroporphyrin (Co(II)TPTPP) with phenanthrene-fused pyrrole rings was synthesized and characterized. Moreover, a detailed analysis of its optical and redox properties was carried out by comparing the results obtained via optical spectroscopy and electrochemistry with the trends predicted via a series of DFT and TD-DFT calculations. The electrochemistry results demonstrated that the π-expanded Co(II)TPTPP interacted strongly with multiwall carbon nanotubes (MWCNTs), which were finally immobilized on carbon nanotubes via noncovalent interactions and further deposited on glassy carbon. This strong immobilization via π–π stacking between Co(II)TPTPP and MWCNTs leads to significantly stable electrochemically catalyzed hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR), which provides a new insight into the understanding electron transfer channels.
- Full Text:
- Date Issued: 2019
Co-encapsulation of rifampicin and isoniazid in crude soybean lecithin liposomes
- Nkanga, Christian I, Noundou, Xavier S, Walker, Roderick B, Krause, Rui W M
- Authors: Nkanga, Christian I , Noundou, Xavier S , Walker, Roderick B , Krause, Rui W M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183536 , vital:44005 , xlink:href="https://doi.org/10.17159/0379-4350/2019/v72a11"
- Description: Despite the well-known anti-mycobacterial actions of isoniazid (INH) and rifampicin (RIF), the clinical success of tuberculosis (TB) therapy requires prolonged administration of multiple drugs in high doses, which often result in frequent adverse effects and low patient adherence. Although liposomes are promising candidates for controlled delivery of anti-TB drug, the high cost of synthetic and highly purified natural lipids currently used in liposomal technology might preclude the universal application of therapeutic liposomes. This work aimed at evaluating the potential of a cost-effective lipid material, crude soybean lecithin (CL), to co-encapsulate RIF and INH for liposomal dual delivery. RIF was encapsulated in CL-liposomes with/without cholesterol using film hydration method, after which INH was incorporated using a freeze–thawing technique. Dynamic light scattering, differential scanning calorimetry, X-ray diffraction and dialysis were used for liposome characterization. Liposomes containing CL alone (CLL) exhibited 90%encapsulation efficiency for RIF and 59%for INH. The mean size and surface charge of CLL were 1114nm and –63mV, respectively. In addition, CLL showed a controlled release profile for the co-encapsulated drugs. CLL would be promising vehicles for macrophage-targeting drug delivery. The present findings demonstrate the feasibility of using CL for preparation of combination products for liposomal delivery.
- Full Text:
- Date Issued: 2019
- Authors: Nkanga, Christian I , Noundou, Xavier S , Walker, Roderick B , Krause, Rui W M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183536 , vital:44005 , xlink:href="https://doi.org/10.17159/0379-4350/2019/v72a11"
- Description: Despite the well-known anti-mycobacterial actions of isoniazid (INH) and rifampicin (RIF), the clinical success of tuberculosis (TB) therapy requires prolonged administration of multiple drugs in high doses, which often result in frequent adverse effects and low patient adherence. Although liposomes are promising candidates for controlled delivery of anti-TB drug, the high cost of synthetic and highly purified natural lipids currently used in liposomal technology might preclude the universal application of therapeutic liposomes. This work aimed at evaluating the potential of a cost-effective lipid material, crude soybean lecithin (CL), to co-encapsulate RIF and INH for liposomal dual delivery. RIF was encapsulated in CL-liposomes with/without cholesterol using film hydration method, after which INH was incorporated using a freeze–thawing technique. Dynamic light scattering, differential scanning calorimetry, X-ray diffraction and dialysis were used for liposome characterization. Liposomes containing CL alone (CLL) exhibited 90%encapsulation efficiency for RIF and 59%for INH. The mean size and surface charge of CLL were 1114nm and –63mV, respectively. In addition, CLL showed a controlled release profile for the co-encapsulated drugs. CLL would be promising vehicles for macrophage-targeting drug delivery. The present findings demonstrate the feasibility of using CL for preparation of combination products for liposomal delivery.
- Full Text:
- Date Issued: 2019
Collaborative stewardship in multifunctional landscapes: toward relational, pluralistic approaches
- Cockburn, Jessica, Cundell, Georgina, Shackleton, Shenoa, Rouget, Mathieu, Zwinkels, Marijn, Cornelius, Susanna A, Metcalf, Liz, van den Broek, D
- Authors: Cockburn, Jessica , Cundell, Georgina , Shackleton, Shenoa , Rouget, Mathieu , Zwinkels, Marijn , Cornelius, Susanna A , Metcalf, Liz , van den Broek, D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/390297 , vital:68535 , xlink:href="https://doi.org/10.5751/ES-11085-240432"
- Description: Landscape stewardship offers a means to put social-ecological approaches to stewardship into practice. The growing interest in landscape stewardship has led to a focus on multistakeholder collaboration. Although there is a significant body of literature on collaborative management and governance of natural resources, the particular challenges posed by multifunctional landscapes, in which there are often contested interests, require closer attention. We present a case study from South Africa to investigate how collaborative stewardship can be fostered in contested multifunctional landscapes. We conducted this research through an engaged transdisciplinary research partnership in which we integrated social-ecological practitioner and academic knowledge to gain an in-depth understanding of the challenges of fostering collaboration. We identified five overarching factors that influence collaboration: contextual, institutional, social-relational, individual, and political-historical. Collaborative stewardship approaches focused on the development of formal governance institutions appear to be most successful if enabling individual and social-relational conditions are in place. Our case study, characterized by high social diversity, inequity, and contestation, suggests that consensus-driven approaches to collaboration are unlikely to result in equitable and sustainable landscape stewardship in such contexts. We therefore suggest an approach that focuses on enhancing individual and social-relational enablers. Moreover, we propose a bottom-up patchwork approach to collaborative stewardship premised on the notion of pluralism. This would focus on building new interpersonal relationships and collaborative capacity through small collective actions. Taking a relational, pluralistic approach to fostering collaborative stewardship is particularly important in contested, socially heterogeneous landscapes. Drawing on our study and the literature, we propose guiding principles for implementing relational, pluralistic approaches to collaborative stewardship and suggest future research directions for supporting such approaches.
- Full Text:
- Date Issued: 2019
- Authors: Cockburn, Jessica , Cundell, Georgina , Shackleton, Shenoa , Rouget, Mathieu , Zwinkels, Marijn , Cornelius, Susanna A , Metcalf, Liz , van den Broek, D
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/390297 , vital:68535 , xlink:href="https://doi.org/10.5751/ES-11085-240432"
- Description: Landscape stewardship offers a means to put social-ecological approaches to stewardship into practice. The growing interest in landscape stewardship has led to a focus on multistakeholder collaboration. Although there is a significant body of literature on collaborative management and governance of natural resources, the particular challenges posed by multifunctional landscapes, in which there are often contested interests, require closer attention. We present a case study from South Africa to investigate how collaborative stewardship can be fostered in contested multifunctional landscapes. We conducted this research through an engaged transdisciplinary research partnership in which we integrated social-ecological practitioner and academic knowledge to gain an in-depth understanding of the challenges of fostering collaboration. We identified five overarching factors that influence collaboration: contextual, institutional, social-relational, individual, and political-historical. Collaborative stewardship approaches focused on the development of formal governance institutions appear to be most successful if enabling individual and social-relational conditions are in place. Our case study, characterized by high social diversity, inequity, and contestation, suggests that consensus-driven approaches to collaboration are unlikely to result in equitable and sustainable landscape stewardship in such contexts. We therefore suggest an approach that focuses on enhancing individual and social-relational enablers. Moreover, we propose a bottom-up patchwork approach to collaborative stewardship premised on the notion of pluralism. This would focus on building new interpersonal relationships and collaborative capacity through small collective actions. Taking a relational, pluralistic approach to fostering collaborative stewardship is particularly important in contested, socially heterogeneous landscapes. Drawing on our study and the literature, we propose guiding principles for implementing relational, pluralistic approaches to collaborative stewardship and suggest future research directions for supporting such approaches.
- Full Text:
- Date Issued: 2019
Conceptualizing, categorizing and recording the outcomes of biological control of invasive plant species, at a population level
- Hoffman, John H, Moran, Cliff V, Hill, Martin P
- Authors: Hoffman, John H , Moran, Cliff V , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423315 , vital:72047 , xlink:href="https://doi.org/10.1016/j.biocontrol.2019.02.005"
- Description: Rates of establishment of agents, their population dynamics after release, and measures of the damage they inflict on their target hosts are all useful indicators of progress and success in weed biological control but cannot account for the overall degree and extent of weed biocontrol achievements (i.e. outcomes) at a plant population level. Current conventions that describe weed biocontrol outcomes as ‘negligible’, ‘partial’, ‘substantial’ or ‘complete’, are often idiosyncratic and imprecise and are inadequate for describing the complexities involved. Using selected examples from South Africa, an extension of the present system is proposed for conceptualizing and categorizing weed biocontrol outcomes more easily; it incorporates four different invasion parameters i.e. density, area, biomass and number of propagules, for different regions and habitats. This approach should help to provide weed biocontrol practitioners with a shared basis for describing, succinctly and with greater precision, the results of their weed biocontrol programs, at a plant population level.
- Full Text:
- Date Issued: 2019
- Authors: Hoffman, John H , Moran, Cliff V , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423315 , vital:72047 , xlink:href="https://doi.org/10.1016/j.biocontrol.2019.02.005"
- Description: Rates of establishment of agents, their population dynamics after release, and measures of the damage they inflict on their target hosts are all useful indicators of progress and success in weed biological control but cannot account for the overall degree and extent of weed biocontrol achievements (i.e. outcomes) at a plant population level. Current conventions that describe weed biocontrol outcomes as ‘negligible’, ‘partial’, ‘substantial’ or ‘complete’, are often idiosyncratic and imprecise and are inadequate for describing the complexities involved. Using selected examples from South Africa, an extension of the present system is proposed for conceptualizing and categorizing weed biocontrol outcomes more easily; it incorporates four different invasion parameters i.e. density, area, biomass and number of propagules, for different regions and habitats. This approach should help to provide weed biocontrol practitioners with a shared basis for describing, succinctly and with greater precision, the results of their weed biocontrol programs, at a plant population level.
- Full Text:
- Date Issued: 2019
Consider the unexpected: Scaling ESD as a matter of learning
- Mickelsson, Martin, Kronlid, David O, Lotz-Sisitka, Heila
- Authors: Mickelsson, Martin , Kronlid, David O , Lotz-Sisitka, Heila
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182438 , vital:43830 , xlink:href="https://doi.org/10.1080/13504622.2018.1429572"
- Description: This article aims to introduce a view of scaling as a learning process. In the article we discuss the concept of ‘scaling up’ or ‘scaling’ of Education for Sustainable Development (ESD) activities on the basis of how ‘scaling up’ ESD is highlighted in the UNESCO Global Action Programme (GAP) on ESD. Drawing on a Deweyan theory of learning as processes of transactional encounters, the article presents a conceptual framework of scaling-ESD-activities-as-learning. This conceptual framework is intended to have implications for ESD policy and ESE research. The theoretical specifications and practical implications presented are results of data collected using a participatory research approach (Re-Solve) and an abductive analysis. In this article, we argue that viewing scaling as a learning process enables a nuanced notion of scaling ESD-activities. This should be seen in relation to (a) complex sustainability challenges, (b) ethical aspects, (c) a more attentive and strict approach to scaling in ESD policy and (d) addressing questions of significant importance to scaling research.
- Full Text:
- Date Issued: 2019
- Authors: Mickelsson, Martin , Kronlid, David O , Lotz-Sisitka, Heila
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/182438 , vital:43830 , xlink:href="https://doi.org/10.1080/13504622.2018.1429572"
- Description: This article aims to introduce a view of scaling as a learning process. In the article we discuss the concept of ‘scaling up’ or ‘scaling’ of Education for Sustainable Development (ESD) activities on the basis of how ‘scaling up’ ESD is highlighted in the UNESCO Global Action Programme (GAP) on ESD. Drawing on a Deweyan theory of learning as processes of transactional encounters, the article presents a conceptual framework of scaling-ESD-activities-as-learning. This conceptual framework is intended to have implications for ESD policy and ESE research. The theoretical specifications and practical implications presented are results of data collected using a participatory research approach (Re-Solve) and an abductive analysis. In this article, we argue that viewing scaling as a learning process enables a nuanced notion of scaling ESD-activities. This should be seen in relation to (a) complex sustainability challenges, (b) ethical aspects, (c) a more attentive and strict approach to scaling in ESD policy and (d) addressing questions of significant importance to scaling research.
- Full Text:
- Date Issued: 2019
Cordidepsine is A Potential New Anti-HIV Depsidone from Cordia millenii
- Zeukang, Rostanie D, Siwe-Noundou, Xavier, Fotsing, Maurice T, Mbafor, Joseph T, Krause, Rui W M, Choudhary, Muhammad I, Atchade, Alex de Theodore
- Authors: Zeukang, Rostanie D , Siwe-Noundou, Xavier , Fotsing, Maurice T , Mbafor, Joseph T , Krause, Rui W M , Choudhary, Muhammad I , Atchade, Alex de Theodore
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193988 , vital:45413 , xlink:href="https://doi.org/10.3390/molecules24173202"
- Description: Chemical investigation of Cordia millenii, Baker resulted in the isolation of a new depsidone, cordidepsine (1), along with twelve known compounds including cyclooctasulfur (2), lup-20(29)-en-3-triacontanoate (3), 1-(26-hydroxyhexacosanoyl)glycerol (4), glyceryl-1-hexacosanoate (5) betulinic acid (6), lupenone (7), β-amyrone (8), lupeol (9), β-amyrin (10), allantoin (11), 2′-(4-hydroxyphenyl)ethylpropanoate (12) and stigmasterol glycoside (13). Hemi-synthetic reactions were carried out on two isolated compounds (5 and 6) to afford two new derivatives, that is, cordicerol A (14) and cordicerol B (15), respectively. The chemical structures of all the compounds were established based on analysis and interpretation of spectroscopic data such as electron ionization mass spectrometry (EI–MS), high resolution electrospray ionization mass spectrometry (HR-ESI–MS), fast atom bombardment mass spectrometry (FAB–MS), one dimension and two dimension nuclear magnetic resonance (1D and 2D-NMR) spectral data as well as X-ray crystallography (XRC). Lupeol ester derivatives [Lup-20(29)-en-3-triacontanoate (3)], monoglycerol derivatives [1-(26-hydroxyhexacosanoyl)glycerol (4) and glyceryl-1 hexacosanoate (5)] were isolated for the first time from Cordia genus while sulfur allotrope [cyclooctasulfur (2)] was isolated for the first time from plant origin. Biological assays cordidepsine (1) exhibited significant anti-HIV integrase activity with IC50 = 4.65 μM; EtOAc extract of stem barks, EtOAc fraction of roots and leaves were not toxic against 3T3 cells.
- Full Text:
- Date Issued: 2019
- Authors: Zeukang, Rostanie D , Siwe-Noundou, Xavier , Fotsing, Maurice T , Mbafor, Joseph T , Krause, Rui W M , Choudhary, Muhammad I , Atchade, Alex de Theodore
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/193988 , vital:45413 , xlink:href="https://doi.org/10.3390/molecules24173202"
- Description: Chemical investigation of Cordia millenii, Baker resulted in the isolation of a new depsidone, cordidepsine (1), along with twelve known compounds including cyclooctasulfur (2), lup-20(29)-en-3-triacontanoate (3), 1-(26-hydroxyhexacosanoyl)glycerol (4), glyceryl-1-hexacosanoate (5) betulinic acid (6), lupenone (7), β-amyrone (8), lupeol (9), β-amyrin (10), allantoin (11), 2′-(4-hydroxyphenyl)ethylpropanoate (12) and stigmasterol glycoside (13). Hemi-synthetic reactions were carried out on two isolated compounds (5 and 6) to afford two new derivatives, that is, cordicerol A (14) and cordicerol B (15), respectively. The chemical structures of all the compounds were established based on analysis and interpretation of spectroscopic data such as electron ionization mass spectrometry (EI–MS), high resolution electrospray ionization mass spectrometry (HR-ESI–MS), fast atom bombardment mass spectrometry (FAB–MS), one dimension and two dimension nuclear magnetic resonance (1D and 2D-NMR) spectral data as well as X-ray crystallography (XRC). Lupeol ester derivatives [Lup-20(29)-en-3-triacontanoate (3)], monoglycerol derivatives [1-(26-hydroxyhexacosanoyl)glycerol (4) and glyceryl-1 hexacosanoate (5)] were isolated for the first time from Cordia genus while sulfur allotrope [cyclooctasulfur (2)] was isolated for the first time from plant origin. Biological assays cordidepsine (1) exhibited significant anti-HIV integrase activity with IC50 = 4.65 μM; EtOAc extract of stem barks, EtOAc fraction of roots and leaves were not toxic against 3T3 cells.
- Full Text:
- Date Issued: 2019
Corrosion resistance of aluminum against acid activation: Impact of benzothiazole-substituted gallium phthalocyanine
- Nnaji, Nnaemeka, Nwaji, Njemuwa N, Mack, John, Nyokong, Tebello
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa N , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187545 , vital:44670 , xlink:href="https://doi.org/10.3390/molecules24010207"
- Description: This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings.
- Full Text:
- Date Issued: 2019
- Authors: Nnaji, Nnaemeka , Nwaji, Njemuwa N , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187545 , vital:44670 , xlink:href="https://doi.org/10.3390/molecules24010207"
- Description: This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings.
- Full Text:
- Date Issued: 2019
Cost-effectiveness of public policy for the long‐term conservation of private lands: What is the deal?
- Nolte, Christopher, de Vos, Alta, Schöttker, Olivier
- Authors: Nolte, Christopher , de Vos, Alta , Schöttker, Olivier
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415837 , vital:71293 , xlink:href="https://www.proquest.com/scholarly-journals/cost-effectiveness-public-policy-long-term/docview/2326874018/se-2"
- Description: Long-term strategies for private-land conservation are experiencing a surge in scholarly attention. This interest is timely and justified. Globally, many important biodiversity values occur on private lands and are therefore subject to private land use decisions that can threaten their persistence in the absence of protection. Public and private actors spend billions of dollars annually to ensure the long-term protection and enhancement of public ecosystem services on private lands. Many governments recognize and strengthen “privately protected areas” (PPAs) as part of long-term protection obligations under the Aichi Biodiversity Targets (Stolton, Redford, and Dudley, 2014). As public policy makers deliberate over the best strategies to enhance private-land protection, they need to understand how cost-effective these different policy options are, and how they compare to each other.
- Full Text:
- Date Issued: 2019
- Authors: Nolte, Christopher , de Vos, Alta , Schöttker, Olivier
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/415837 , vital:71293 , xlink:href="https://www.proquest.com/scholarly-journals/cost-effectiveness-public-policy-long-term/docview/2326874018/se-2"
- Description: Long-term strategies for private-land conservation are experiencing a surge in scholarly attention. This interest is timely and justified. Globally, many important biodiversity values occur on private lands and are therefore subject to private land use decisions that can threaten their persistence in the absence of protection. Public and private actors spend billions of dollars annually to ensure the long-term protection and enhancement of public ecosystem services on private lands. Many governments recognize and strengthen “privately protected areas” (PPAs) as part of long-term protection obligations under the Aichi Biodiversity Targets (Stolton, Redford, and Dudley, 2014). As public policy makers deliberate over the best strategies to enhance private-land protection, they need to understand how cost-effective these different policy options are, and how they compare to each other.
- Full Text:
- Date Issued: 2019
Could enemy release explain invasion success of Sagittaria platyphylla in Australia and South Africa?
- Kwong, Raelene M, Sagliocco, Jean L, Harms, Nathan E, Butler, Kym L, Martin, Grant D, Green, Peter T
- Authors: Kwong, Raelene M , Sagliocco, Jean L , Harms, Nathan E , Butler, Kym L , Martin, Grant D , Green, Peter T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419298 , vital:71632 , xlink:href="https://doi.org/10.1016/j.aquabot.2018.11.011"
- Description: Sagittaria platyphylla (delta arrowhead) is an emergent aquatic macrophyte native to southeastern United States of America that has been introduced into Australia and South Africa as an ornamental pond and aquarium plant. Compared to plants in the native range, S. platyphylla in the introduced range have greater reproductive capacity and form extensive infestations that dominate shallow waterbodies. One explanation for the invasive success of S. platyphylla in introduced countries is that plants are devoid of biotic pressures that would regulate population abundance in their native range (the enemy release hypothesis). We previously reported on field surveys that documented the number of pathogens and insect herbivores associated with S. platyphylla in native and introduced ranges. Here, we quantify the damage caused by these natural enemies to S. platyphylla in the two ranges. As predicted, damage to plants caused by pathogens and insect herbivores was much greater in the native than the introduced range at both the plant and population level. In introduced regions herbivory was low (less than 10%) in every plant part, while in North America insect damage to fruiting heads was 46% (of fruiting heads attacked), damage to leaves was between 33 to 57%, and internal herbivore damage to petioles and the inflorescence scapes was 56% and 43% respectively. Pathogen damage to leaves was between 39 to 57% of leaves per plant affected, compared to 9% in Australia and 8% in South Africa. This lack of biotic resistance from herbivores and disease may have facilitated S. platyphylla invasion in Australia and South Africa.
- Full Text:
- Date Issued: 2019
- Authors: Kwong, Raelene M , Sagliocco, Jean L , Harms, Nathan E , Butler, Kym L , Martin, Grant D , Green, Peter T
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/419298 , vital:71632 , xlink:href="https://doi.org/10.1016/j.aquabot.2018.11.011"
- Description: Sagittaria platyphylla (delta arrowhead) is an emergent aquatic macrophyte native to southeastern United States of America that has been introduced into Australia and South Africa as an ornamental pond and aquarium plant. Compared to plants in the native range, S. platyphylla in the introduced range have greater reproductive capacity and form extensive infestations that dominate shallow waterbodies. One explanation for the invasive success of S. platyphylla in introduced countries is that plants are devoid of biotic pressures that would regulate population abundance in their native range (the enemy release hypothesis). We previously reported on field surveys that documented the number of pathogens and insect herbivores associated with S. platyphylla in native and introduced ranges. Here, we quantify the damage caused by these natural enemies to S. platyphylla in the two ranges. As predicted, damage to plants caused by pathogens and insect herbivores was much greater in the native than the introduced range at both the plant and population level. In introduced regions herbivory was low (less than 10%) in every plant part, while in North America insect damage to fruiting heads was 46% (of fruiting heads attacked), damage to leaves was between 33 to 57%, and internal herbivore damage to petioles and the inflorescence scapes was 56% and 43% respectively. Pathogen damage to leaves was between 39 to 57% of leaves per plant affected, compared to 9% in Australia and 8% in South Africa. This lack of biotic resistance from herbivores and disease may have facilitated S. platyphylla invasion in Australia and South Africa.
- Full Text:
- Date Issued: 2019
Cryptic species of a water hyacinth biological control agent revealed in South Africa: host specificity, impact, and thermal tolerance
- Paterson, Iain D, Coetzee, Julie A, Weyl, Philip, Griffith, Tamzin C, Voogt, Nina, Hill, Martin P
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
- Authors: Paterson, Iain D , Coetzee, Julie A , Weyl, Philip , Griffith, Tamzin C , Voogt, Nina , Hill, Martin P
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/423982 , vital:72113 , xlink:href="https://doi.org/10.1111/eea.12812"
- Description: The discovery that cryptic species are more abundant than previously thought has implications for weed biological control, as there is a risk that cryptic species may be inadvertently released with consequences for the safety of the practice. A cryptic species of a biological control agent released for the control of the invasive alien macrophyte, water hyacinth, Eichhornia crassipes (C. Mart.) Solms. (Pontederiaceae), was recently discovered in South Africa. The two species were considered a single species prior to genetic analysis and interbreeding experiments. The original biological control agent retains the name Eccritotarsus catarinensis (Carvalho) (Heteroptera: Miridae) whereas the new species has been described as Eccritotarsus eichhorniae Henry. In this study, we compared the host specificity, efficacy, and thermal physiologies of the two species. The host specificity of the two species within the Pontederiaceae was very similar and both are safe for release in South Africa. Comparison of the per capita impact of the two species indicated that E. eichhorniae was the more damaging species but this is likely to be influenced by temperature, with E. catarinensis being more effective under lower temperatures and E. eichhorniae being more effective under higher temperatures. Releasing the correct species for the thermal environment of each release site will improve the level of control of water hyacinth in South Africa. This example highlights the need to keep populations of biological control agents from different native range collection localities separate, and to screen for host specificity and efficacy.
- Full Text:
- Date Issued: 2019
Deactivation of field cultivation in communal areas of South Africa: Patterns, drivers and socio-economic and ecological consequences
- Shackleton, Charlie M, Mograbi, Penelope, Drimie, Scott, Fay, Derick, Hebinck, Paul, Hoffman, Michael T, Maciejewski, Kristine, Twine, Wayne
- Authors: Shackleton, Charlie M , Mograbi, Penelope , Drimie, Scott , Fay, Derick , Hebinck, Paul , Hoffman, Michael T , Maciejewski, Kristine , Twine, Wayne
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398210 , vital:69384 , xlink:href="https://doi.org/10.1016/j.landusepol.2019.01.009"
- Description: Smallholder production is a significant contributor to rural livelihoods and rural economies in much of the developing world. Yet, there is evidence of increasing disengagement in some regions, including southern Africa. However, there has been little consideration of the rates and the livelihood, ecological and policy implications of such. In this paper we examine previous studies on rates of deactivation of crop fields by smallholders in the communal areas of South Africa, supported by repeat photo images and case study material. Together these various methods show that it is a widespread phenomenon occurring at variable rates. Over short periods deactivation of crop fields can be balanced through some reactivation or intensification of homegardens. But over longer periods there is a net decline in the area of fields cultivated in many areas, with corresponding increases in the area of fallow land which, through time, may undergo changes towards more natural vegetation. We review the drivers of this deactivation of field cropping, and then contemplate the possible socio-economic and ecological implications at local and national scales. We show that there are numerous and profound implications that require greater understanding and policy responses.
- Full Text:
- Date Issued: 2019
- Authors: Shackleton, Charlie M , Mograbi, Penelope , Drimie, Scott , Fay, Derick , Hebinck, Paul , Hoffman, Michael T , Maciejewski, Kristine , Twine, Wayne
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/398210 , vital:69384 , xlink:href="https://doi.org/10.1016/j.landusepol.2019.01.009"
- Description: Smallholder production is a significant contributor to rural livelihoods and rural economies in much of the developing world. Yet, there is evidence of increasing disengagement in some regions, including southern Africa. However, there has been little consideration of the rates and the livelihood, ecological and policy implications of such. In this paper we examine previous studies on rates of deactivation of crop fields by smallholders in the communal areas of South Africa, supported by repeat photo images and case study material. Together these various methods show that it is a widespread phenomenon occurring at variable rates. Over short periods deactivation of crop fields can be balanced through some reactivation or intensification of homegardens. But over longer periods there is a net decline in the area of fields cultivated in many areas, with corresponding increases in the area of fallow land which, through time, may undergo changes towards more natural vegetation. We review the drivers of this deactivation of field cropping, and then contemplate the possible socio-economic and ecological implications at local and national scales. We show that there are numerous and profound implications that require greater understanding and policy responses.
- Full Text:
- Date Issued: 2019
Design, evaluation and optimization of taste masked clarithromycin powder
- Ntemi, Pascal V, Walker, Roderick B, Khamanga, Sandile M
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
- Authors: Ntemi, Pascal V , Walker, Roderick B , Khamanga, Sandile M
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183503 , vital:44001 , xlink:href="https://doi.org/10.1691/ph.2019.8116"
- Description: Clarithromycin (CLA) is an extremely bitter macrolide antibiotic used to treat paediatric and adult infections. The bitter taste affects patient adherence and may compromise therapy. This research developed a taste masked CLA resinate using Indion® 234, a weak acidic cation exchange resin. The factors affecting formation of the CLA-resin complex were assessed. Design of experiments was used to optimize response while evaluating input variables such as temperature, CLA-resin ratio,stirring time and pH. CLA loading efficiency was determined spectrophotometrically and CLA release using USP Apparatus II. Differential Scanning Calorimetry (DSC), Scanning Electron Microscop (SEM), Fourier Transform Infrared (FT-IR) Spectroscopy and X-ray Diffraction (XRD) were used to confirm complex formation. A spectrophotometric method was used to assess taste evaluation. The optimum CLA-resin ratio, temperature, and stirring time were 1:4, 80 °C, 3 hours, respectively, at pH 8. Characterization techniques revealed that CLA was crystalline and the complex amorphous in nature. FT-IR spectra of resinate revealed the absence of resonance due to the tertiary amine functional group that is responsible for the bitter taste of CLA. CLA was stable in simulated salivary fluid and was released within 3 hours in gastric fluid. All CLAresin batches revealed complete taste masking. Taste analysis highlighted the improvement of taste masking properties of the resinate as the CLA to resin ratio, increased.
- Full Text:
- Date Issued: 2019
Development and Validation of a Stability-indicating RP-HPLC Method Using Quality by Design for Estimating Captopril
- Veerubhotla, Krishna, Walker, Roderick B
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
- Authors: Veerubhotla, Krishna , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183525 , vital:44003 , xlink:href="10.4172/pharmaceutical-sciences.1000478"
- Description: The applicability of a quality by design framework for the development of a sensitive, simple and selective, stability-indicating reversed-phase high-performance liquid chromatography analytical method for the analysis of captopril was investigated. Design of experiments using a central composite design approach was used for method development. Twenty experimental runs were performed with acetonitrile content ranging between 28 and 36 % v/v, pH from 2.8 to 3.6 and temperature between 22° and 32°. The experimental data obtained was used to derive a quadratic model for the retention time of captopril. The optimized method produced sharp peaks with good resolution (>2) for captopril and the internal standard with retention times of 3.1 and 6.2 min, respectively. The experimental data revealed that acetonitrile content in the mobile phase and pH are significant factors that affect the retention time and resolution of captopril. Normal probability plots revealed that the residual and predicted data fall approximately on a straight line, indicating that the experimental error for these studies was evenly distributed suggesting that the model could be used to navigate the design space. This approach is useful to expedite method development and optimization activities in analytical laboratories.
- Full Text:
- Date Issued: 2019
Development, manufacture and characterization of niosomes for the delivery for nevirapine
- Witika, Bwalya A, Walker, Roderick B
- Authors: Witika, Bwalya A , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183514 , vital:44002 , xlink:href="https://doi.org/10.1691/ph.2019.8168"
- Description: Nevirapine (NVP), used for the treatment of HIV/AIDS, exhibits unpredictable oral bioavailability, has a poor side effect profile and requires frequent dosing. Niosomes are novel drug delivery systems that have the potential to overcome these challenges. A thin layer hydration approach was used to produce niosomes and optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) establish and identify parameters that may affect the manufacture of niosomes. The impact of cholesterol and surfactant content, hydration time and temperature on manufacture was investigated. Critical quality attributes (CQA) in respect of particle size (PS), entrapment efficiency (EE), polydispersity index (PDI) and the amount of NVP released at 48 hours was also assessed. The optimised niosome composition was identified and manufactured and the CQA characterised prior to placing the batch on stability for 12 weeks at 4±2 °C and 22±2 °C. The PS, PDI, EE and % NVP released at 48 h was 523.36±23.16 nm, 0.386±0.054, 96.8 % and 25.3 % for niosomes manufactured with Span® 20. Similarly, the parameters were 502.87±21.77 nm and 0.394±0.027, 98.0 % and 25.0 % for mean PS, PDI, EE and %NVP released at 48 h for Span® 80 niosomes. All characterisation was undertaken on the day of manufacture. In conclusion, a simple, cheap, rapid and precise method of manufacture of NVP niosomes was developed, validated and optimised using DoE and RSM and the product exhibited the target CQA.
- Full Text:
- Date Issued: 2019
- Authors: Witika, Bwalya A , Walker, Roderick B
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/183514 , vital:44002 , xlink:href="https://doi.org/10.1691/ph.2019.8168"
- Description: Nevirapine (NVP), used for the treatment of HIV/AIDS, exhibits unpredictable oral bioavailability, has a poor side effect profile and requires frequent dosing. Niosomes are novel drug delivery systems that have the potential to overcome these challenges. A thin layer hydration approach was used to produce niosomes and optimisation was undertaken using design of experiments (DoE) and response surface methodology (RSM) establish and identify parameters that may affect the manufacture of niosomes. The impact of cholesterol and surfactant content, hydration time and temperature on manufacture was investigated. Critical quality attributes (CQA) in respect of particle size (PS), entrapment efficiency (EE), polydispersity index (PDI) and the amount of NVP released at 48 hours was also assessed. The optimised niosome composition was identified and manufactured and the CQA characterised prior to placing the batch on stability for 12 weeks at 4±2 °C and 22±2 °C. The PS, PDI, EE and % NVP released at 48 h was 523.36±23.16 nm, 0.386±0.054, 96.8 % and 25.3 % for niosomes manufactured with Span® 20. Similarly, the parameters were 502.87±21.77 nm and 0.394±0.027, 98.0 % and 25.0 % for mean PS, PDI, EE and %NVP released at 48 h for Span® 80 niosomes. All characterisation was undertaken on the day of manufacture. In conclusion, a simple, cheap, rapid and precise method of manufacture of NVP niosomes was developed, validated and optimised using DoE and RSM and the product exhibited the target CQA.
- Full Text:
- Date Issued: 2019
Dual phototransformation of the pollutants methyl orange and Cr (VI) using phthalocyanine-cobalt ferrite based magnetic nanocomposites
- Mapukata, Sivuyisiwe, Osifeko, Olawale L, Nyokong, Tebello
- Authors: Mapukata, Sivuyisiwe , Osifeko, Olawale L , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187059 , vital:44561 , xlink:href="https://doi.org/10.1016/j.heliyon.2019.e01509"
- Description: Bifunctional nanocomposites based on zinc phthalocyanines and glutathione capped CoFe2O4 magnetic nanoparticles (GSH-CoFe2O4 MNPs) are applied in a binary system wherein simultaneous photooxidation of methyl orange (MO) and photoreduction of Cr (VI) are conducted. The photoactivity of two zinc Pcs with different functional moieties are compared based on their interactions with GSH-CoFe2O4 MNPs. Conjugation of the Pcs to the GSH-CoFe2O4 MNPs not only enhanced their singlet oxygen production but also their photocatalytic activity in both photooxidation and photoreduction experiments. Using electron paramagnetic resonance (EPR) spectroscopy, the Pc-MNP conjugates reported herein were found to exhibit superparamagnetic behaviour, giving the advantage of easy separation using an external magnetic field post application, an attractive attribute for heterogeneous catalysis. The catalysts reported herein are therefore good candidates as catalysts for real life water purification analyses as they facilitate the treatment of both organic and inorganic water pollutants.
- Full Text:
- Date Issued: 2019
- Authors: Mapukata, Sivuyisiwe , Osifeko, Olawale L , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187059 , vital:44561 , xlink:href="https://doi.org/10.1016/j.heliyon.2019.e01509"
- Description: Bifunctional nanocomposites based on zinc phthalocyanines and glutathione capped CoFe2O4 magnetic nanoparticles (GSH-CoFe2O4 MNPs) are applied in a binary system wherein simultaneous photooxidation of methyl orange (MO) and photoreduction of Cr (VI) are conducted. The photoactivity of two zinc Pcs with different functional moieties are compared based on their interactions with GSH-CoFe2O4 MNPs. Conjugation of the Pcs to the GSH-CoFe2O4 MNPs not only enhanced their singlet oxygen production but also their photocatalytic activity in both photooxidation and photoreduction experiments. Using electron paramagnetic resonance (EPR) spectroscopy, the Pc-MNP conjugates reported herein were found to exhibit superparamagnetic behaviour, giving the advantage of easy separation using an external magnetic field post application, an attractive attribute for heterogeneous catalysis. The catalysts reported herein are therefore good candidates as catalysts for real life water purification analyses as they facilitate the treatment of both organic and inorganic water pollutants.
- Full Text:
- Date Issued: 2019
Effect of bromination on the optical limiting properties at 532 nm of BODIPY dyes with p-benzyloxystyryl groups at the 3, 5-positions
- Ngoy, Bokolombe P, May, Aviwe K, Mack, John, Nyokong, Tebello
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187507 , vital:44665 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.08.012"
- Description: The optical limiting (OL) properties of 3,5-di-p-benzyloxystyrylBODIPY dyes that contain both protons and bromine atoms at the 2,6-positions have been investigated by using the Z-scan technique at 532 nm on the nanosecond timescale. There is relatively weak absorbance at 532 nm under ambient light conditions, because the incorporation of p-benzyloxystyryl groups at the 3,5-positions results in a ca. 140 nm red shift of the main BODIPY spectral band to the 640–670 nm range. Reverse saturable absorbance (RSA) profiles that are consistent with an excited state absorption (ESA) mechanism involving the T1 and/or S1 states are observed in CH2Cl2 solution. Second order hyperpolarizability values of ca. 8 × 10−30 esu are obtained and this demonstrates that the dyes are potentially suitable for use in OL applications at 532 nm. There is a slight enhancement of the OL properties upon bromination, due to increased intersystem crossing to the triplet manifold, but the enhancement of the OL properties is less significant than has been observed with metal phthalocyanine complexes.
- Full Text:
- Date Issued: 2019
- Authors: Ngoy, Bokolombe P , May, Aviwe K , Mack, John , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187507 , vital:44665 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.08.012"
- Description: The optical limiting (OL) properties of 3,5-di-p-benzyloxystyrylBODIPY dyes that contain both protons and bromine atoms at the 2,6-positions have been investigated by using the Z-scan technique at 532 nm on the nanosecond timescale. There is relatively weak absorbance at 532 nm under ambient light conditions, because the incorporation of p-benzyloxystyryl groups at the 3,5-positions results in a ca. 140 nm red shift of the main BODIPY spectral band to the 640–670 nm range. Reverse saturable absorbance (RSA) profiles that are consistent with an excited state absorption (ESA) mechanism involving the T1 and/or S1 states are observed in CH2Cl2 solution. Second order hyperpolarizability values of ca. 8 × 10−30 esu are obtained and this demonstrates that the dyes are potentially suitable for use in OL applications at 532 nm. There is a slight enhancement of the OL properties upon bromination, due to increased intersystem crossing to the triplet manifold, but the enhancement of the OL properties is less significant than has been observed with metal phthalocyanine complexes.
- Full Text:
- Date Issued: 2019
Effect of gold nanoparticle shape on the photophysicochemical properties of sulphur containing metallophthalocyanines
- Dube, Edith, Nyokong, Tebello
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187048 , vital:44559 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.12.091"
- Description: In this work tetrakise[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakise[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.
- Full Text:
- Date Issued: 2019
- Authors: Dube, Edith , Nyokong, Tebello
- Date: 2019
- Subjects: To be catalogued
- Language: English
- Type: text , article
- Identifier: http://hdl.handle.net/10962/187048 , vital:44559 , xlink:href="https://doi.org/10.1016/j.molstruc.2018.12.091"
- Description: In this work tetrakise[(thiopheneethoxy) phthalocyaninato] zinc(II) (1), tetrakise[(thiopheneethoxy) phthalocyaninato] indium (II) chloride (2), tetrakis [(benzo [d]thiazol-2-yl phenoxy) phthalocyaninato] zinc(II) (3), and tetrakis [(benzo [d]thiazol-2-yl phenoxy)phthalocyaninato] indium (II) chloride (4) were linked to both gold nanospheres (AuNSs) and gold nanotriangles (AuNTs) via Au-S and Au-N (the latter for complexes 3 and 4 only) self assembly. The photophysicochemical behaviour of complexes and their conjugates were studied. The conjugates yielded improved triplet and singlet quantum yields, with nanospheres displaying better properties than nanotriangles. The conjugates with a benzothiazole phenoxy substituent also yielded better properties than their thiophene ethoxy counterpart. These conjugates especially those with a benzothiazole phenoxy substituent have potential as photosensitisers for photodynamic therapy applications.
- Full Text:
- Date Issued: 2019