Ethnobotanical Survey And In Vitro Evaluation Of Antimicrobial Activity Of Plants Traditionally Used As Herbs And Spices From Kabbe Constituencies In Zambezi Region, Namibia

ABSTRACT

The aims of this study were to conduct an ethnobotanical survey on indigenous knowledge of plants traditionally used as herbs and spices in Kabbe constituencies of the Zambezi region, evaluate their antimicrobial activity, determine their synergistic effects, and further elucidate their potential mechanism of action. Using semistructured interviews and closed-end questionnaires, ethnobotanical data were collected from local informants in fourteen villages of Kabbe constituencies between December 2018 and April 2019. Plant samples were extracted with 1:1 ratio of dichloromethane:methanol (DCM:MeOH) and double distilled water before evaluated against laboratory strains of Candida albicans, Saccharomyces cerevisiae, Staphylococcus aureus, Bacillus cereus, Listeria monocytogenes, Clostridium perfringens, Enterococcus faecalis, Escherichia coli, Salmonella typhimurium, Shigella sonnei, Pseudomonas aeruginosa and Proteus vulgaris using disc diffusion assay, minimum inhibitory concentration (MIC), time-kill synergistic study, permeability of cell membrane, and measurement of release of 260 nm absorbing materials and proteins. Twenty-three plant species belonging to 16 plant families were documented. Cleome gynandra (83.8) and Hibiscus mechowii (77.9) were widely used species. DCM:MeOH extracts of C. gynandra had the lowest MIC value of 6.25 mg/mL against both B. cereus, E. faecalis, E. coli, C. perfringens, S. typhimurium, P. aeruginosa, P. vulgaris, C. albicans and S. cerevisiae. Meanwhile, the water extracts of Eucalyptus sp. showed the lowest MIC value of 6.25 mg/mL against both E. coli, S. typhimurium and P. vulgaris. Twenty-three synergistic effects were observed with S. cerevisiae, S. typhimurium, S. aureus, P. vulgaris, P. aeruginosa, E. coli, and C. perfringens. The 2 × MIC of Nymphaea lotus exhibited the greatest electric conductivity at 4 and 6 hours, leaked DNA materials and proteins at 4, 8, 12 and 24 hours against C. albicans. Our results contributed data to the gap in the knowledge and availability of scientific information regarding plants traditionally used as herbs and spices in Kabbe constituencies of the Zambezi region. Toxicity studies are needed to support the safe usage of these plants as food additives and natural preservatives for food safety applications.