Anticancer, Antioxidant And Antimicrobial Screening Of Extracts From Ziziphus Mucronata, Heliotropium Ciliatum And Gnidia Polycephala From The Oshikoto Region Of Namibia

ABSTRACT

Plants have long been used to treat ailments such as headaches, stomach-ache, diarrhoea, tumours, wounds and sexually transmitted diseases, just to mention a few. Ziziphus mucronata, Heliotropium ciliatum and Gnidia polycephala are traditionally used to treat tumours and wound-related illnesses. Tumours and persistent wounds can be a sign of cancer. Microbial wound infections can also bring fatal consequences if unattended. This study evaluates the antioxidant, anticancer and antimicrobial potential of extracts of these three plants. The leaves (Z. mucronata) and aerial parts (G. polycephala and H. ciliatum) were collected from Oshikoto region, grinded and sequentially extracted with hexane, dichloromethane, ethanol and methanol. Water extracts were also prepared. The antioxidant potential was evaluated by 1,1-diphenyl-picrylhydrazyl (DPPH) assay whereas the Brine shrimp lethality test (BST), 3-(4,5-dimethylthiazol-2-yl)-2,5- diphenyltetrazolium bromine (MTT) assay and APOPercentageTM flow cytometry assay were used to evaluate the anticancer potential of the extracts. The antimicrobial potential of the plant extracts against eight wound pathogens: Candida albicans, Clostridium tetani, Escherichia coli, Methillicin-resistant Staphylococcus aureus, Mycobacterium terrae, Pseudomonas aeruginosa, Staphylococcus epidermidis and Streptococcus A, was evaluated using the broth micro-dilution method. Methanol extracts of Z. mucronata and G. polycephala showed good antioxidant activity, comparable to that of a control, butylated hydroxyl toluene. Dichloromethane and hexane extracts of Z. mucronata and H. ciliatum as well as ethanol extracts of H. ciliatum showed high cytotoxicity, with LC50 values < 250 µg/ mL. Water extracts showed the least cytotoxic activity. In addition, dichloromethane extract of Z. mucronata also demonstrated a broad spectrum antimicrobial activity, obtaining MIC values ≤ 1 mg/ mL against six of the eight tested pathogens. The low toxicity of water extracts of the three plants and the antimicrobial activity recorded validates the use of these extracts in traditional medicine. Some extracts also appears to be good sources of potential antioxidant and anticancer agents. However, more studies are required.