ANTIMICROBIAL PROPERTIES, PHYTOCHEMICAL COMPOSITION AND CYTOTOXICITY OF Launaea cornuta, Maesa lanceolata and Bidens pilosa

Abstract

Drug resistant pathogenic microorganisms have become an emerging clinical and public health challenge globally. Medicinal plants contain natural products of therapeutic value to human health due to their antimicrobial properties. Bidens pilosa dried leaf decoctions are used in Marakwet traditional medicine to treat skin infections and wounds. Launaea cornuta leaves and roots are used by the Suba people in Kenya to treat opportunistic diseases associated with HIV/AIDS. Maesa lanceolata is used in the Kenyan indigenous medical practice in the treatment of helminthes, bacterial and fungal infections. However, their antimicrobial properties and/or safety have not been scientifically evaluated. The main objective of the study was to determine the in vitro antimicrobial efficacy of Maesa lanceolata, Bidens pilosa and Launaea cornuta against pathogenic strains of Shigella dysentriae, Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Candida glabrata, Aspergillus flavus, Trychophyton mentagrophytes and Microsporum gypseum. The antibacterial and antifungal activity of methanol, dichloromethane and water extracts of the roots, stem and leaves of the plants against the test microorganisms was carried out using Kirby Bauer disc diffusion technique and acute toxicity evaluated using Vero E6 cell lines. Minimum inhibitory concentration was determined by broth microdilution method. The presence of phytochemicals was determined using thin layer chromatography. Data obtained from the study was analyzed using multifactorial Analysis of variance. Results showed that the four fungal pathogens were inhibited significantly by the methanolic, dichloromethane and water extracts of the plants with the exception of Aspergillus flavus that was not inhibited. Water extracts of the root and stem bark of Maesa lanceolata were significantly active with P-value of 0.0000 against C. glabrata ATCC 24433 strain with inhibition zone diameter and minimum inhibitory concentration values of 23.33mm, 31.25 mg/ml and 19.67mm, 125mg/ml respectively. Bacterial bioassays inhibition zone diameter and minimum inhibitory concentration values ranged between 6-21mm, 3.91-500 mg/ml respectively. The phytochemicals present in the leaves, stems and roots included alkaloids, phenols, terpenoids, anthraquinones and tannins. The selected leaves (dichloromethane and methanol) extracts and stem bark (dichloromethane and aqueous) extracts displayed cytotoxicity on Vero E6 cell lines with cytotoxicity concentration ranging between 206 - 684 μg/ml. Herbalists and the public would benefit from the information disseminated concerning the minimum inhibitory concentration to be administered to patients, which parts of the plants are most effective against infection-causing pathogenic bacteria, fungi and safety of the extracts .