A study on the medicinal potential of Artemisia afra, a traditionally used herb in Namibia

A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science in Biology

The use of plants as medicines to relieve various symptoms, as well as to manage and cure ailments has been recorded since ancient times. Much interest in these ethnomedicinal plants stems from their long-standing use in traditional medicine. They are still regarded as making important contributions to health care even though great advances have been made in modern medicine. Traditionally, Artemisia afra (‘Wilde als’) is used to treat the common cold, flu and coughs, as well as nasal congestion. During the COVID-19 pandemic, communities in Namibia used ‘Wilde als’ as a treatment for the disease. Little is known about the efficacy and safety of ‘Wilde als’ found in Namibia. This study aimed to identify the bioactive classes of compounds for ‘Wilde als’; as well as to determine the antioxidant, anti-inflammatory, and antiviral activities and the cytotoxic properties of the plant. Extracts of ‘Wilde als’ were prepared by aqueous and organic extraction methods, using water and a mixture of methanol and dichloromethane (1:1 v/v). The phytochemical profile was determined using thin-layer chromatography. The total flavonoid content within the extracts was also determined. The albumin denaturation assay was used for determining the in vitro anti-inflammatory response of the extracts of ‘Wilde als’ using egg albumin derived from a fresh hen’s egg as the protein source. The DPPH antioxidant assay was used to determine the radical scavenging activity of the plant extracts using 2,2-diphenyl-1- picryl-hydrazyl-hydrate also known as DPPH, and the MTT cytotoxicity assay was used to determine the cellular reduction of the tetrazolium salt, 3-(4,5-dimethylthiazol- 2-yl)-2,5-diphenyltetrazolium bromide, also known as MTT. The Vero E6 cell line, a kidney epithelial cell line was used to determine cell proliferation and survival during the MTT assay. The in vitro antiviral effects of the plant extracts against a pseudovirus of SARS-CoV-2 were determined by calculating the reduction of the SAR-CoV-2 in ii the Vero E6 cells. The extracts of the ‘Wilde als’ possessed flavonoids, coumarins, saponins, steroids and terpenoids, with TFC with the highest at 19.89 % for the organic extracts of the twigs. The extracts of A. afra exhibited significant antioxidant activities ranging from 0.1029 to 9.4197 μg/ml with the highest activity observed for the aqueous extract of the leaves. The extracts of A. afra also exhibited significant anti- inflammatory activity. The highest anti-inflammatory activity of the plant extracts was observed for the organic extract from the combination of the leaves and twigs (87.5 % at 100 μg/ml). The plant extracts displayed antiviral potential against the beta-strain of the SARS-CoV 2 virus, with the organic extracts exhibiting higher inhibition of the viral load with EC50 values of 48.84 μg/ml (leaf extracts), 24.65 μg/ml (twig extracts) and 251.67 μg/ml (combination of the leaves and twigs extracts). The results of the MTT cytotoxicity assay indicated that the aqueous extracts showed little to no cytotoxicity; the organic extracts on the other hand showed high cytotoxicity with IC50 values of 134.12 μg/ml (leaves and twigs), followed by 151.53 μg/ml (twigs) and 182.31 μg/ml (leaves). The findings of this study suggest that ‘Wilde als’ has the potential to be used as an antiviral agent with antioxidant and anti-inflammatory activities as the possible mechanisms of action, with low cytotoxic effects for the aqueous extracts. The organic extracts, however, were cytotoxic, but when used in the correct doses, they can have significant health benefits. This study also provides evidence that the use of ‘Wilde als’ an herbal remedy in the south of Namibia is rational and consistent with research from other regions of Africa