An investigation into the impact of geographical location on the phytochemical composition, pharmacological and toxicological activities of Tulbaghia violacea collected from the Eastern Cape and Gauteng Province
- Authors: Kader, Tasmeera
- Date: 2024-10-11
- Subjects: Tulbaghia violacea , Phytochemicals , Alliaceae Geographical distribution , Diabetes , Alzheimer's disease
- Language: English
- Type: Academic theses , Master's theses , text
- Identifier: http://hdl.handle.net/10962/461819 , vital:76242
- Description: Introduction: The number of communicable and non-communicable diseases continues to rise and has become more prevalent. While drugs exist to manage and/ or treat majority of the communicable and non-communicable diseases, the rise in disease prevalence puts pressure on researchers to find new drug molecules to treat and manage these ailments. Traditional medicine refers to the knowledge, skills and practices which are based on the beliefs and experiences indigenous to cultures and is used to maintain health. Most of the research into traditional medicine focuses on the medicinal plants used. Medicinal plants are any plants in which one or more of its organs contain substances which are used for therapeutic purposes or for the synthesis of drugs. Tulbaghia violacea is a monocotyledonous genus of herbaceous perennial bulbs which is native to Africa and can be readily found throughout South Africa. It is popular for its antimicrobial, antifungal, anticoagulant, antioxidant and anticancer properties. It has been that ecological factors influence the composition and quantity of phytochemicals present in a plant. Aim of the study: The aim of the study was to investigate the impact of geographical location on the phytochemical composition, pharmacological and toxicological activities of T. violacea collected from the Eastern Cape and Gauteng Province. Methods: The leaves of T. violacea were collected from the Eastern Cape and Gauteng Province. The leaves were dried and extracted using serial maceration with solvents hexane, acetone and methanol. The resulting extracts were subjected to qualitative preliminary phytochemical analysis and a quantitative total phenol content test was carried out using gallic acid as the standard. Thin layer chromatography (TLC) was performed to identify classes of compounds present in T. violacea. xix Antioxidant activity of T. violacea was determined qualitatively using a dot-plot and quantitatively using a DPPH radical scavenging activity assay. Ascorbic acid was used as the standard. Anti-diabetic properties of T. violacea were assessed using an α- amylase inhibition assay and an α- glucosidase inhibition assay. Acarbose was used as the standard for these assays. The anti-Alzheimer properties of T. violacea leaf extracts was determined using and acetylcholinesterase (AChE) inhibition assay. Donepezil was used as the standard for this assay. The DPPH radical scavenging activity, the α- amylase inhibition assay, the α- glucosidase inhibition assay and the AChE inhibition assay was combined with linear regression to determine the IC50 values of the T. violacea extracts and the standards. Statistical analysis was conducted to determine any differences between the plant samples and the standards as well as any differences between the EC and GP sample. Results: The results of the qualitative phytochemical analysis revealed the presence of saponins, flavonoids, tannins, alkaloids, steroids, cardiac glycosides and phenolic compounds present in T. violacea collected from EC and GP. However, their presence in the samples were different based on where the plant was cultivated. The results of the total phenolic content test, revealed that the hexane, acetone and methanol extracts of T. violacea contained phenolic compounds with the highest quantity of phenolic compounds being present in the methanol extracts. Significant statistical difference in total phenolic content between the EC and GP samples were seen for the hexane and methanol extracts. The results of the TLC revealed the presence of multiple bands which confirmed the presence of multiple phytochemicals in T. violacea. All of the extracts of T. violacea from EC and GP, showed antioxidant activity using both the dot-plot and the DPPH radical scavenging activity assay. The highest DPPH radical scavenging activity was seen by the hexane extract of the EC sample of T. violacea. The results showed significant statistical difference between the DPPH radical scavenging activity of the EC and GP samples. , Thesis (Msc (Pharmacy)) -- Faculty of Pharmacy, Pharmacy, 2024
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- Date Issued: 2024-10-11
Inhibitor search and variant analysis of Acetylcholinesterase
- Authors: Ras, Harnaud
- Date: 2021-04
- Subjects: Acetylcholinesterase , Alzheimer's disease , Acetylcholinesterase -- Inhibitors , Alzheimer's disease -- Chemotherapy , Cerebrovascular disease -- Treatment , Molecular mechanics Poisson–Boltzmann surface area (MM-PBSA)
- Language: English
- Type: thesis , text , Masters , MSc
- Identifier: http://hdl.handle.net/10962/178191 , vital:42919
- Description: Acetylcholinesterase (AChE) inhibition is used to treat Alzheimer's disease by increasing the availability of acetylcholine to carry nerve signals in the brain. The response to this treatment varies widely, which may be due to altered affnity to the current drugs caused by genetic variation. Various negative side-effects limit their use. As this is one of the only available therapeutic drug targets to treat Alzheimer's disease, decreasing the negative effects is of great importance. AChE is involved in biological processes that occur after acute ischemic stroke. Stroke is the third leading cause of death worldwide, and 87% of all stroke cases belong to ischemic stroke. AchEI (cholinesterase inhibitors) have been suggested to have properties that lower the risk of stroke. AChE is one of 15 verified drug targets under study for treatment of stroke. In addition to Alzheimer's disease and stroke, Lewy body disease (LBD) may be treated using cholinesterase inhibitors. The goals of this study are to find inhibitors that can potentially be used to treat Alzheimer's disease and/or stroke and to investigate variants which may affect protein dynamics and function. Two variants were analyzed, P247L and T229S. Molecular simulation of the P247L variant resulted in a disruption in protein dynamics in comparison to the wildtype. A total of 5728 molecules were screened and 10 nanosecond simulations were used to narrow down the set of compounds. The four best performing molecules were simulated for 10 nanoseconds. MM-PBSA was performed to identify molecules with high binding free energies. , Thesis (MSc) -- Faculty of Science, Biochemistry and Microbiology, 2021
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- Date Issued: 2021-04
Neuronal nitric oxide synthase : a biomarker for Alzheimers disease : interaction of neuronal nitric oxide synthase with beta-amyloid peptides in the brain
- Authors: Padayachee, Eden Rebecca
- Date: 2011 , 2013-07-19
- Subjects: Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:4086 , http://hdl.handle.net/10962/d1007677 , Alzheimer's disease , Nitric-oxide synthase , Biochemical markers , Amyloid beta-protein , Peptide hormones
- Description: High levels of the amino acid arginine and low levels of the product citrulline in the cerebrospinal fluid of Alzheimer's patients could mean that there is a decrease in the enzymes that metabolize this amino acid. One such enzyme is neuronal nitric oxide synthase (nNOS). In this study, neuronal nitric oxide synthase (nNOS), sourced from bovine brain was extracted and concentrated using two methods of precipitation: poly (ethylene glycol) 20 000 (PEG) and ammonium sulphate [(NH₄)₂S0₄). These two techniques gave no increase in yield nor fold purification and hence were abandoned in favour of ion exchange chromatography by DEAE-Sepharose. The enzyme was then successfully purified by anion-exchange and after dialysis produced a 38% yield and three fold purification and yielded the highest specific activity of 2.27 U/mg. Neuronal nitric oxide synthase (nNOS) was a heterodimeric protein with a total molecular mass of ± 225 kDa (95 and 130 kDa monomers). The temperature and pH optima of the enzyme were 40⁰C and 6.5, respectively. The kinetic parameters (KM and Vmax) of nNOS were 70 μM and 0.332 μmol.min⁻¹, respectively. Moreover neuronal nitric oxide synthase (nNOS) was relatively stable at 40⁰C (t½ = 3 h). It was also confirmed that β-amyloid peptides inhibited nNOS when bound to the enzyme and that nNOS behaved as a catalyst in fibril formation through association-dissociation between enzyme and β-amyloid peptide. It was further shown that Aβ₁₇₋₂₈ inhibited nNOS the most with a Ki of 1.92 μM and also had the highest Stern-Volmer value (Ksv) of 0.11 μM⁻¹ indicating tight binding affinity to nNOS and easier accessibility to fluor molecules during binding. Congo red, turbidity, thioflavin-T assays and transmission electron microscopy were successfully used to detect and visualize the presence of fibrils by studying the process of fibrillogenesis. Computerized molecular modeling successfully studied protein dynamics and conformational changes of nNOS. These results correlated with resonance energy transfer (FRET) results which revealed the distance of tryptophan residues from the arginine bound at enzyme active site. Both the aforementioned techniques revealed that in the natural state of the enzyme with arginine bound at the active site, the tryptophan residues (TRP₆₂₅ and TRP₇₂₁) were positioned at the surface of the enzyme 28 Å away from the active site. When the amyloid peptide (Aβ₁₇₋₂₈) was bound to the active site, these same two amino acids moved 14 Å closer to the active site. A five residue hydrophobic fragment Aβ₁₇₋₂₁ [Leu₁₇ - Val₁₈ - Phe₁₉ - Phe₂₀ - Ala₁] within Aβ₁₇₋₂₈ was shown by computer modeling to be critical to the binding of the peptide to the active site of nNOS.
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- Date Issued: 2011