Antioxidant and antibacterial activities of ethanol extract and flavonoids isolated from Athrixia phylicoides

The ethanol extract of A. phylicoides was investigated for its antioxidant activity using the DPPH scavenging method. The extract showed good antioxidant results with a EC50 value of 10.64 ± 0.0842 µ/ml. The extract was also tested for antibacterial activity against microorganisms (Staphylococcus aureus, Enterococus faecalis, Bacillus cereus, Bacillus subtilis, Bacillus pumilus, Pseudomonas aeruginosa, Escherichia coli, Klebsiella pneumonia) commonly known to pose a threat in the wellbeing of man. All tested microorganisms were significantly inhibited by the extract with the MIC values ranging from 3.13 µg/ml to 6.25 µg/ml. Folin-Ciocalteu’s reagent method was used to determine total phenolic content of dried and freshly prepared crude extract of A. phylicoides. Higher total phenolic content (28.28 ± 0.019 mg GAC/100g) and antioxidant activity (EC50, 10.64 ± 0.084 µg/ml) was observed in the dried extract compared to the fresh extract with a TPC value of 23.04 ± 0.003 mg GAC/100g and EC50 of 13.97 ± 0.066 µg/ml. Bioassay-guided fractionation of ethanolic extract from aerial parts of Athrixia phylicoides using silica and sephadex column chromatography led to the isolation of four known flavanoids, 5-hydroxy-6,7,8,3’,4’,5’-hexamethoxyflavon-3-ol (1), 3-0- demethyldigicitrin (2), 5,6,7,8,3’,4’-hexamethoxyflavone (3) and Quecertin (4). Due to the low yield, no further tests were done on compound 3. A DPPH-scavenging assay was performed to evaluate the antioxidant activity of the isolated compounds. All the tested compounds showed potent antioxidant activity with EC50 values ranging from 1.27 to 3.41 µg/ml. Compound 4 showed a higher antioxidant activity (EC50, 1.27 µg/ml) than vitamin C (EC50, 2.66 µg/ml) used as a control. The MIC values of the isolated compounds against tested microorganisms varied from 20 to more than 40 µg/ml. All the tested compounds showed no activity against S. aureus, B. pumilus, K. pneumonia and P. aeruginosa at the highest concentration tested (40 µg/ml). These compounds together with the extract were further analyzed by XTT assay on Vero cells. The extract showed a low toxicity effect on the cells at lower concentrations exhibiting EC50 value of 107.8 ± 0.129 µg/ml. Compound 4 showed minimal toxicity effect on the cells with a EC50 value of 81.38±0.331 µg/ml, compared to Compound 1 and 2 which exhibited EC50 values of 27.91 ± 0.181 µg/ml and 28.92 ± 0.118 µg/ml respectively. The results obtained from this study provide a clear rationale for the medicinal uses of Athrixia phylicoides.Dissertation (MSc)--University of Pretoria, 2010.Plant Scienceunrestricte

Screening for adulticidal activity against Anopheles arabiensis in ten plants used as mosquito repellent in South Africa

BACKGROUND : Due to the development of resistance to synthetic insecticides, adverse effects to human health, non-target organisms and the environment, there is an urgent need to develop new insecticides, which are effective, safe, biodegrable and target-specific. This study was undertaken to evaluate the adulticidal activity of 10 plants used traditionally as mosquito repellents in South Africa. METHODS : The dried plant materials were extracted with dichloromethane (DCM) and ethanol (EtOH). The extracts were evaluated for adulticidal activity against Anopheles arabiensis mosquitoes, a potent malaria vector in South Africa. Adult mortality was observed after 24 hours of exposure. RESULTS : All the extracts showed adulticidal activity. The highest activity was observed in both DCM and EtOH extracts of Aloe ferox leaves with 98 and 86% mosquito mortality, respectively. The DCM extract of A. ferox leaves was then subjected to a dose-dependent bioassay to determine the EC50 value. The extract exhibited an EC50 value of 4.92 mg/ml. CONCLUSION : The results of the present study showed that the DCM extract of A. ferox leaves may have the potential to be used as an insecticide against An. arabiensis. Further studies to isolate and identify active compounds are in progress.The South African Medical Research Councilhttp://www.malariajournal.com/content/13/1/173am201

COVID-19 vaccine demand protest might have increased vaccine acceptance and uptake in South Africa

Safe and efficacious COVID-19 vaccines exist, but their success against the disease depends on public willingness to receive them. Vaccine hesitancy is one major obstacle to the achievement of herd immunity. On 25 June 2021, about 2000 supporters of the Economic Freedom Fighters (EFF) (the third biggest political party in South Africa) marched to the offices of the national regulatory authority (NRA) supporting COVID-19 vaccination and demanding approval of two additional vaccines (Sputnik V and Sinovac) in South Africa. The march was led by EFF leader, Julius Malema. By then, only three COVID-19 vaccines had received emergency use authorization in the country—the Janssen, AstraZeneca and Pfizer-BioNtech vaccines. It is worth noting that NRAs should only approve a vaccine if they are satisfied that its benefits outweigh any potential risks and not through political pressure. Nevertheless, we believe that this march might have increased COVID-19 vaccine acceptance and uptake among EFF supporters. The endorsement of COVID-19 vaccines by Malema, an influential political figure in South Africa, probably convinced some vaccine hesitant South Africans that COVID-19 vaccination is important. Therefore, we suggest vaccine endorsement by influential individuals in South Africa as one of the strategies to increase COVID-19 vaccine uptake

Antioxidant activity and cytotoxicity effect of flavonoids isolated from athrixia phylicoides

Bioassay-guided fractionation of an ethanolic extract from aerial parts of Athrixia phylicoides using silica and sephadex column chromatography led to the isolation of three flavonoids. The compounds were identified as: 5-hydroxy-6,7,8,3’,4’,5’-hexamethoxyflavon-3-ol (1), 3-0-demethyldigicitrin (2), and Quecertin (3). Isolated compounds together with ethanol crude extract were tested for antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl (DPPH)-spectrophotometric assay, while cytotoxicity effect was determined using XTT colorimetric assay. The crude extract showed a concentration-dependent radical scavenging activity with EC50 value of 10.64 ± 0.08 μg/ml. Compound 3 was the most potent radical scavenger, exhibiting EC50 value of 1.27 ± 0.25 μg/ml, followed by compound 1 and 2 showing 2.74 ± 0.10 and 3.41 ± 0.09 μg/ml respectively. The crude extract showed no or little toxicity on Vero cells at lower concentrations tested exhibiting the IC50 value of 107.8 ± 0.13 μg/ml. Compound 3 showed minimal toxicity effect by exhibiting IC50 value of 81.38 ± 0.33 μg/ml as compared to compound 2 (IC50, 28.92 ± 0.12 μg/ml) and compound 1 (IC50, 27.91 ± 0.18 μg/ml). The results obtained from this study provide a clear rationale for the medicinal uses of A. phylicoides