Evaluation Of Pharmacological Properties Of Traditional Medicinal Plants Used For The Treatment Of Cancer By South African And Lesotho Communities

Abstract

The aim of this study was to assess Asparagus laricinus, Senecio asperulus and Gunnera perpensa which are used to treat cancer as antibacterial, antioxidant, anti-inflammatory, anticancer and antimutagenicity agents. Medicinal plants extracts were prepared through maceration with methanol, water, Dichloromethane (DCM), methanol: dichloromethane and hexane as solvents. Secondary metabolites were assessed qualitatively, while antibacterial activities were determined using the disk diffusion assay, and the 2, 2- diphenyl-1-picrylhydrazyl (DPPH) assay was used to evaluate antioxidant activity. The lipopolysaccharide (LPS) stimulated RAW 264.7 mouse macrophage in vitro model was used to evaluate the anti-inflammatory activity of these three plants, with resveratrol used as a positive control. All extracts were tested in vitro for growth inhibitory effects against human prostate cancer (PC3), human breast cancer (MCF-7) and the non-cancerous African green monkey kidney (Vero) cell lines using the MTT assay. Cell cycle analysis was performed on two extracts (methanol and dichloromethane) with selective anticancer properties to elucidate their mechanism of action. Mutagenic and antimutagenic properties were determined by the Comet assay using hepatic cells, and Vitotox test using Salmonella typhimurium genotoxicity (recN2-4) and cytotoxicity (pr1) strains, with and without S9 metabolic activation. To describe distinctive chemical features of Asparagus laricinus and Senecio asperulus crude extracts, Liquid chromatography-mass spectrometry (LC-MS) analysis was performed. Asparagus laricinus inhibited bacterial growth of all selected micro-organisms. However, Staphylococcus species were resistant even at 500 μg/ml. Methanol extracts of Senecio asperulus inhibited microbial growth at the concentration of 50 μg/ml. The dichloromethane extract of Senecio asperulus was active on most bacteria with MICs between 50 μg/ml and 500 μg/ml. Nonetheless, the water and methanol extracts of Gunnera perpensa had no activity against all organisms tested. Methanolic and aqueous extracts of Asparagus laricinus showed good antioxidant activity. Aqueous extracts of Senecio asperulus and Gunnera perpensa showed free radical scavenging activity yielding EC50 values of 100 μg/ml and 25 μg/ml, respectively. The aqueous extracts of Senecio asperulus showed moderate anti-inflammatory activity from 50 to 200 μg/ml, while the methanol extracts were active at 200 μg/ml and with no cytotoxicity. Asparagus laricinus showed weak anti-inflammatory activity when compared with resveratrol. No anti-inflammatory activity was observed from all Gunnera perpensa, suggesting that this species may be using other mechanisms for anti-inflammatory activity. Asparagus laricinus methanol and Senecio asperulus dichloromethane extracts exhibited cytotoxicity activity against breast cancer cells with IC50 values of 97.6 μg/mL and 69.15 μg/mL, respectively. Gunnera perpensa DCM extract also showed cytotoxicity on prostate and breast cancer cells, with less activity on Vero cells. Cell cycle analysis suggested that Asparagus laricinus methanol extract induced cell death selectively through apoptosis observed from Annexin V-FITC and PI stain. Cell cycle analysis also showed that Senecio asperulus DC. dichloromethane extracts induced breast cancer cells death through cell arrest at the synthesis phase and G2 phase. Senecio asperulus dichloromethane extracts further showed cytotoxicity activity against prostate cancer cells with IC50 values of 69.25 μg/mL due to cell arrest at the G2 and early mitotic (G2/M) phase. The results obtained from the Vitotox test for Asparagus laricinus, Senecio asperulus, and Gunnera perpensa correlated well with results obtained from NRU and Comet assays. All the tested extracts had no toxicity and genotoxicity in vitro, except the dichloromethane extracts from Senecio asperulus and Gunnera perpensa which were found to be cytotoxic but not genotoxic after S9 metabolic activation. None of the tested extracts had antigenotoxic properties. Gunnera perpensa extracts showed more polyphenols than Asparagus laricinus and Senecio asperulus. The LCMS results of these plant extracts showed the presence of twelve known compounds such as Luteolin 7-O-rutinoside, and Rutin, and twenty-eight unknown compounds from Asparagus laricinus. Senecio asperulus had nineteen unknown compounds and two known compounds; chlorogenic acid isomer, and dicaffeoyl quinic acid. Deductions made from the anticancer analysis propose that the methanol extract of Asparagus laricinus is a suitable aspirant for future breast cancer chemotherapeutic drug, due to its selective cytotoxicity on cancer cells and not on non-cancerous cells. Furthermore, the anticancer activities of Asparagus laricinus, Senecio asperulus and Gunnera perpensa observed were not from the protection against genotoxicity as none of these plants had genotoxic properties. Moreover, the negative genotoxicity highlighted the safe use of Asparagus laricinus, Senecio asperulus and Gunnera perpensa as medicinal plants. Results from this study were encouraging; especially for Asparagus laricinus as a potential anti-breast cancer agent, despite the need for clinical studies to confirm the pharmacological activities of these plants and toxicological effects in vivo.