Antimicrobial, antioxidant, anticancer, and phytochemical analysis of South African medicinal plants collected from the Senwabarwana area, Limpopo province

Abstract

The antimicrobial resistance (AMR) of many microorganisms to conventional antibiotics poses a serious threat to human health. The situation is further compounded by the development of tumours arising from complex infections and vice versa due to an immunocompromised immune system. The objective of the study is to assess the antimicrobial, antioxidant, anticancer, and phytochemical components of the selected medicinal plants’ extracts. The microdilution broth assay was used to evaluate the antimicrobial activity of the organic extracts against food-borne and human-infecting pathogens. Additionally, the anti-proliferative effects of the extracts were evaluated in vitro using a tetrazolium-based calorimetric (MTT) assay against a line of human colorectal carcinoma (Caco-2), human breast adenocarcinoma (MCF-7), and human cervical cancer cells (HeLa). Additionally, 2,2-Diphenyl-1-Picrylhydrazyl (DPPH), 2,2′-Azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), and possible iron chelation were used to measure the extracts’ antioxidant activity. Gas chromatography time-of-flight mass spectrometry (GC-TOF-MS) was used to evaluate the phytochemical analysis. Talinum caffrum (Thumb. Eckl. & Zeyhr.) extract exhibited the lowest minimum inhibitory concentration (MIC) value of 0.05 mg/ml against Salmonella arizonae, while extracts from Cassia abbreviata Oliv. subsp. beareana (Holmes) Brenan and Peltophorum africanum Sond. exhibited a similar MIC value against Shigella flexneri. P. africanum extracts exhibited a potent inhibition of the MCF-7 cell line, yielding an IC50 value of 1.80 µg/ml. In comparison, T. caffrum extracts exhibited an LC50 value of 5.66 µg/ml against the HeLa cell line and a notable LC50 value of 1.12 and 1.11 µg/ml against DPPH and Fe2+, respectively. The organic extract from T. caffrum contains 4-methyl-2,4-bis(p-hydroxyphenyl) pent-1-ene (20.803%), 2-furancarboxylic acid, 2-methylbutyl ester (16.909%), and 2-methylbutyl ester (13.702%). The selected medicinal plants exhibited a potent antimicrobial, antioxidant, and anticancer activity. The observed results, in a way, support the use of the selected medicinal plant species in treating various infections, as complementary and alternative medicines, particularly against opportunistic microbes and cancer by improving and supporting the immune system through many means, such as quenching free radicals, alleviating tumour and microbial growth.