Isolation and characterization of antiplasmodial metabolites from South African marine alga
- Authors: Afolayan, Anthonia Folake
- Date: 2008
- Subjects: Malaria -- Africa Antimalarials -- Therapeutic use Malaria -- Prevention Malaria -- Drug therapy Marine algae -- Therapeutic use Natural products -- Therapeutic use Plasmodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3739 , http://hdl.handle.net/10962/d1003063
- Description: Malaria is one of the three most deadly diseases in Africa. Although there are available treatments, their efficacy has been greatly reduced over the past two decades due to the development of resistance to currently available drugs. This has necessitated the search for new and effective antimalarial agents. This project approached the search for new antimalarial compounds in two ways: (i) by screening natural products isolated from marine algae against the Plasmodium parasite and (ii) by modification of selected isolated active compounds to target 1-deoxY-đ-xylulose 5-phosphate reductoisomerase (DXR), an enzyme found in the nonmevalonate isoprenoid biosynthetic pathway of Plasmodium Jalciparum. It was envisaged that such a compound would exhibit dual action on the Plasmodium parasite. Extracts obtained from 22 marine algae were prefractionated by solvent partitioning and were screened for anti plasmodial activity against the chloroquine sensitive (CQS) P. Jalciparum D 10 strain. Overall, 50% of the algae screened produced at least one crude fraction with activity against P. Jalciparum. Extracts of the algae Sargassum heterophyllum, Plocamium cornutum, Amphiroa ephedrea and Pterosiphonia cloiophylla gave the most promising results. Fractionation of S. heterophyllum afforded three tetraprenyltoluquinols (3.1, 3.2 and 3.5) and an all-trans-fucoxanthin (3.6). Three new compounds (4.5, 4.6 and 4.7) and two known halogenated monoterpenes (4.1 and 4.4) were isolated from P. cornutum. Each of the isolated compounds from both S. heterophyllum and P. cornutum showed antiplasmodial activity with IC₅₀ values ranging from 2.0 - 15.3 μM for S. heterophyllum and 13 - 230 μM for P. cornutum. Attempts to synthetically modify halogenated monoterpene 4.4 by dihydroxylation and phosphorylation in order to inhibit the DXR enzyme was unsuccessful. However, the hemiterpene analogue (5.42) of the halogenated monoterpenes was successfully phosphorylated and dihydroxylated to give compound 5.45 which showed promising activity against DXR. The result obtained indicated that the proposed phosphorylation and dihydroxylation of the halogenated monoterpene 4.4 would result in the synthesis of a potent DXR inhibitor and therefore a potential antimalarial agent with dual mode of action on the Plasmodium parasite.
- Full Text:
- Authors: Afolayan, Anthonia Folake
- Date: 2008
- Subjects: Malaria -- Africa Antimalarials -- Therapeutic use Malaria -- Prevention Malaria -- Drug therapy Marine algae -- Therapeutic use Natural products -- Therapeutic use Plasmodium
- Language: English
- Type: Thesis , Masters , MSc
- Identifier: vital:3739 , http://hdl.handle.net/10962/d1003063
- Description: Malaria is one of the three most deadly diseases in Africa. Although there are available treatments, their efficacy has been greatly reduced over the past two decades due to the development of resistance to currently available drugs. This has necessitated the search for new and effective antimalarial agents. This project approached the search for new antimalarial compounds in two ways: (i) by screening natural products isolated from marine algae against the Plasmodium parasite and (ii) by modification of selected isolated active compounds to target 1-deoxY-đ-xylulose 5-phosphate reductoisomerase (DXR), an enzyme found in the nonmevalonate isoprenoid biosynthetic pathway of Plasmodium Jalciparum. It was envisaged that such a compound would exhibit dual action on the Plasmodium parasite. Extracts obtained from 22 marine algae were prefractionated by solvent partitioning and were screened for anti plasmodial activity against the chloroquine sensitive (CQS) P. Jalciparum D 10 strain. Overall, 50% of the algae screened produced at least one crude fraction with activity against P. Jalciparum. Extracts of the algae Sargassum heterophyllum, Plocamium cornutum, Amphiroa ephedrea and Pterosiphonia cloiophylla gave the most promising results. Fractionation of S. heterophyllum afforded three tetraprenyltoluquinols (3.1, 3.2 and 3.5) and an all-trans-fucoxanthin (3.6). Three new compounds (4.5, 4.6 and 4.7) and two known halogenated monoterpenes (4.1 and 4.4) were isolated from P. cornutum. Each of the isolated compounds from both S. heterophyllum and P. cornutum showed antiplasmodial activity with IC₅₀ values ranging from 2.0 - 15.3 μM for S. heterophyllum and 13 - 230 μM for P. cornutum. Attempts to synthetically modify halogenated monoterpene 4.4 by dihydroxylation and phosphorylation in order to inhibit the DXR enzyme was unsuccessful. However, the hemiterpene analogue (5.42) of the halogenated monoterpenes was successfully phosphorylated and dihydroxylated to give compound 5.45 which showed promising activity against DXR. The result obtained indicated that the proposed phosphorylation and dihydroxylation of the halogenated monoterpene 4.4 would result in the synthesis of a potent DXR inhibitor and therefore a potential antimalarial agent with dual mode of action on the Plasmodium parasite.
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The development and evaluation of a cohesion-building programme for a South African male collegiate basketball team
- Authors: Razafimbola, Sandimampita
- Date: 2008
- Subjects: Teamwork (Sports) Basketball teams College sports Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3040 , http://hdl.handle.net/10962/d1002549
- Description: There is a general consensus among sport coaches and practitioners that it is better to work with a cohesive team. Research on cohesion has provided positive links between cohesion and performance as well as the overall well-being of the team and its members. The purpose of this study is to develop and evaluate a cohesion-building programme under an Action Research paradigm. The Group Environment Questionnaire, in parallel with focus group discussions were used to assist in the development and evaluation of a cohesion-building programme tailored to the specific needs of the Rhodes University men’s basketball 1st team. The team is known to be a good team but it was missing something that made it become great. Fostering higher cohesiveness was deemed to be the missing link to the chain of success. Various changes were brought to the 1) team structure, 2) team processes, 3) team environment to enhance the team’s cohesiveness levels. It was found that the programme was positive and powerful in that it accelerated the process of cohesion building within the team. It was also found that the programme had the power to transcend demographical barriers and unite people from diverse backgrounds. Finally, the programme increased the team’s performance level and enabled it to achieve objectives that were never achieved by any other men’s basketball team at Rhodes University before. Naturally there are going to be some ups and downs, especially if you have individuals trying to achieve at a high level. But when we stepped in between the lines, we knew what we were capable of doing. When a pressure situation presented itself, we were plugged into one another like a cohesive unit. That’s why we were able to come back so often and win so many close games. And that’s why we were able to beat more talented team. - Michael Jordan (former Chicago Bulls; NBA Hall of Famer).
- Full Text:
- Authors: Razafimbola, Sandimampita
- Date: 2008
- Subjects: Teamwork (Sports) Basketball teams College sports Sports -- Psychological aspects
- Language: English
- Type: Thesis , Masters , MSocSc
- Identifier: vital:3040 , http://hdl.handle.net/10962/d1002549
- Description: There is a general consensus among sport coaches and practitioners that it is better to work with a cohesive team. Research on cohesion has provided positive links between cohesion and performance as well as the overall well-being of the team and its members. The purpose of this study is to develop and evaluate a cohesion-building programme under an Action Research paradigm. The Group Environment Questionnaire, in parallel with focus group discussions were used to assist in the development and evaluation of a cohesion-building programme tailored to the specific needs of the Rhodes University men’s basketball 1st team. The team is known to be a good team but it was missing something that made it become great. Fostering higher cohesiveness was deemed to be the missing link to the chain of success. Various changes were brought to the 1) team structure, 2) team processes, 3) team environment to enhance the team’s cohesiveness levels. It was found that the programme was positive and powerful in that it accelerated the process of cohesion building within the team. It was also found that the programme had the power to transcend demographical barriers and unite people from diverse backgrounds. Finally, the programme increased the team’s performance level and enabled it to achieve objectives that were never achieved by any other men’s basketball team at Rhodes University before. Naturally there are going to be some ups and downs, especially if you have individuals trying to achieve at a high level. But when we stepped in between the lines, we knew what we were capable of doing. When a pressure situation presented itself, we were plugged into one another like a cohesive unit. That’s why we were able to come back so often and win so many close games. And that’s why we were able to beat more talented team. - Michael Jordan (former Chicago Bulls; NBA Hall of Famer).
- Full Text:
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