Antimicrobial activities of crude extracts from selected medicinal climbers against Candida albicans, Pseudomonas aeruginosa and Staphylococcus aureus

Antimicrobial resistance (AMR) is a major global health threat to humans, and combating it is increasingly challenging. Recent studies suggest that plant-derived antimicrobials could be effective in combating AMR. Commonly used as herbal medicine, Adenia lobata, Ipomoea aquatica, and Rubia cordifolia are climbers with significant medicinal value for treating or managing various human diseases and conditions. This study aimed to evaluate the effect of methanol leaf, stem, and root extracts of these climbers on the growth of Candida albicans, Pseudomonas aeruginosa, and Staphylococcus aureus. Plant samples were collected from Kisii, the shores of Lake Victoria-Kisumu, and Maseno University farm in Kenya, then shade-dried and extracted with methanol. Antimicrobial efficacy of the extracts was assessed using disc diffusion method at 25, 50, 75, and 100 mg/ml concentrations along with the determination of minimum inhibitory concentration (MIC) at 0.625, 1.25, 2.5, 5 and 10 mg/ml concentrations, minimum bactericidal concentration (MBC), and minimum fungicidal concentration (MFC). Data was subjected to analysis of variance (ANOVA) followed by T-test analysis. Means were separated and compared using the least significant difference (LSD) at P≤0.05. Largest zones of inhibition were observed in 100 mg/ml R. cordifolia leaf extract against P. aeruginosa (21.00 mm), and S. aureus (15.57 mm), and 100 mg/ml R. cordifolia root extract against C. albicans (11.67 mm). MIC values for R. cordifolia extracts against C. albicans was 5 mg/ml for both leaf and root extracts and 10 mg/ml for the stem whereas for both P. aeruginosa and S. aureus they were all at 10 mg/ml. However, neither MBC nor MFC was observed. These research findings suggest that A. lobata, I. aquatica, and R. cordifolia have potential as antimicrobial agents, particularly R. cordifolia, with antimicrobial properties linked to phytochemicals like anthraquinones, terpenoids, alkaloids, and phenolic compounds, supporting their use in traditional herbal medicine.