Antimicrobial activity and qualitative phytochemical composition of crude extracts from medicinal plants against selected enteric bacterial pathogens and candida albicans
Opinde, Hibert Rachuonyo
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Plant extracts with medicinal value have been used to treat many diseases that can either be bacterial, fungal or parasitic among many others. Plants with medicinal value produce certain chemical elements known as phytochemicals that have antimicrobial activity. Enteric bacterial pathogens are disease-causing microorganisms that are usually located in the intestinal tracts of either animal or human beings. The pathogenic members are usually associated with infections that are characterized by; enteric fevers, abdominal pain, diarrhoea, and vomiting. Candida albicans is a yeast fungus that is mainly found in the mucosal cavity of the vagina and intestinal tract as a normal microbiota but it can cause systematic infections in immunocompromised individuals. This study was aimed at determining the antimicrobial activity, combined effects of the selected plant leaf extracts of Tagetes minuta, Aloe secundiflora, Vernonia lasiopus and Bulbine frutescens against selected clinical isolates of Escherichia coli, Salmonella typhi, Staphylococcus aureus, Shigella flexineri, Enterococcus faecalis and Candida albicans obtained from Kenyatta University Health Centre; using the Kirby-Bauer method. In addition, qualitative analysis of the phytochemicals present in the extracts was also determined. The plants materials were obtained from Kenyatta University arboretum and identified by Taxonomist; Prof L.E. Newton and voucher specimen deposited in the University herbarium. The collected data was then analyzed in SAS version 9.1 using ANOVA and further subjected to a post hoc test with P<0.05 being considered significant. When used singly and in combinations against the test microorganisms the average zones of inhibition were found to be significant at P<0.05. When the plant extracts were used in low concentrations against the test microorganisms; Vernonia lasiopus was more active against Shigella flexineri (MIC 3.3μg/ml, MBC 7.1μg/ml), Bulbine frutescens against Shigella flexineri (MIC 3.2μg/ml, MBC 6.2μg/ml), Aloe secundiflora against Shigella flexineri (MIC 3.7μg/ml, MBC 8.0μg/ml) and Tagetes minuta against Enterococcus faecalis (MIC 5.1μg/ml, MBC 6.3μg/ml)*. The combining of the extracts also showed an increased and decreased antimicrobial activity with the interactions being significant; P<0.05. The average zone of inhibition formed by Aloe secundiflora and Tagetes minuta plant leaf extracts combination (8.67±1.86mm) showed a decrease in antimicrobial activity as compared to when Tagetes minuta (15.17±2.71mm) and Aloe secundiflora (17.00±2.10mm) respectively when used against Candida albicans. The qualitative phytochemical analysis showed the presence of four phytochemicals; saponins, tannins, alkaloids, and flavonoids. The study provides insight into the antimicrobial activities of the plant extracts and their use in the treatment of bacterial or fungal infections. This information might be used in herbal medicine in making concoctions to maximize their effectiveness. There is a need to elucidate the actual compounds in the plant leaf extracts responsible for the antimicrobial activity so that can be used in drug development.