The incidence of drug resistance is an expanding global issue that necessitates the search for novel drug substitutes. Humans have used traditional medicinal plants (TMPs) for thousands of years to treat a variety of diseases, such as cancer and microbial infections. The scientific validation of therapeutic effects of TMPs aided in the development of complementary and alternative therapies for a variety of medical conditions. The therapeutic nature of TMPs can be attributed to phytochemicals. Kigelia africana (K. africana) and Pterocapus angolensis (P. angolensis) are medicinal plants found throughout Southern Africa. They are used in these countries to treat a variety of diseases such as rheumatic conditions, stomach ailments, infertility, cancer, inflammation, dysentery, and sexually transmitted infections (STIs). In this study, we extracted phytochemicals (as crude extracts) from K. africana and P. angolensis in Botswana. We then assessed their antioxidant, antimicrobial, and anticancer properties. The crude extracts from leaves, barks, roots, and fruits of the two plants were prepared through maceration using distilled water (aqueous), methanol, ethyl acetate, and hexane. Total phenolic content (TPC) and total flavonoid content (TFC) of the crude extracts were determined using the Folin Ciocalteu (F-C) and aluminum chloride (AlCl3) colorimetric assays respectively. The antioxidant activity and capacity of the crude extracts were evaluated using the 2,2-Diphenyl 1-picrylhydrazyl (DPPH) free radical scavenging assay, ferric reducing antioxidant power (FRAP) assay, and Phosphomolybdenum inhibition total antioxidant capacity (TAC) assay. The Kirby Bauer Disc diffusion method and the serial micro-dilution method were used to assess the antimicrobial activity of crude extracts. In-silico analysis was used to investigate the anticancer properties of K. africana and P. angolensis. Protein-ligand molecular docking was used to analyze the site-specific binding interaction of K. africana and P. angolensis phytochemicals with the epidermal growth factor receptor (EGFR). Drug-likeness analysis and Absorption, Distribution, Metabolism, Excretion, and Toxicity (ADME/Tox) predictions were used to further assess the safety of the top-performing phytochemicals. A significantly higher TPC was observed in P. angolensis bark aqueous extract (556.2 ± 3.7 µg gallic acid equivalent (GAE)/mg dry extract (DE)), while a significantly higher TFC was observed in K. africana leaves ethyl acetate extract (445.1 ± 1.6 µg quercetin equivalence (QE)/mg (DE)). Pterocarpus angolensis bark methanol extract exhibited significantly higher DPPH radical scavenging xvi activity (87.2 ± 0.084 % and DPPH IC50 of 3 ± 3 µg/mL), FRAP activity (1042.2 ± 133.2 µg GAE/mg DE) and Phosphomolybdenum inhibition TAC (2206.5 ± 14 µg GAE/mg DE). TPC, TFC, and antioxidant activity were positively correlated. Both plants exhibited antimicrobial activity. Kigelia africana crude extracts exhibited broad spectrum antimicrobial activity. Yohimbine, Digoxigenin and Lupeol phytochemicals showed high affinity to EGFR (≥ 8.7 kcal/mol) and they showed promising drug-like and ADME/Tox properties.

Thesis (MSc Biological Sciences and Biotechnology)--Botswana International University of Science and Technology, 2023