Background and objective: Microbial drug resistance is a growing health problem. This has led to search for new antimicrobial compound and plants are considered as one of the most promising sources for new antimicrobials discovery. Pyrenacantha grandiflora (P. grandiflora) Baill is used for the treatment and management of diarrhea, gastrointestinal related infections, dysentery, inflammation and tooth pain by traditional healers in the Venda region. The goal of the present study was to evaluate the antimicrobial activity of P. grandiflora tubers using different extraction solvents against 15 bacterial and 11 fungal strains.
Materials and methods: Plant extracts were obtained using 5 solvents separately, boiled water, cold water, methanol, dichloromethane, chloroform and ethyl acetate. Hole plate assay was used for initial evaluation of antimicrobial properties of plant materials. Minimum inhibitory concentrations (MIC) of the most active plant extracts were determined by the broth microdilution method. One-way ANOVA was used for data analysis.
Results: The hole plate assay revealed that the highest antibacterial activity was against Micrococcus kristinae with ethyl acetate extract and no extract was active against Candida and Fusarium species using this method. The MIC of the extracts was determined and all the extracts showed antimicrobial activity against all tested strains ranging from 0.06-7.5 mg mL-1. Some extract appeared to be fungicidal and hot water extract were more active against Cryptococcus neoformans with the MFC value of 0.06 mg mL-1. Methanol extract was also active against most test strains including Candida tropicalis with the minimum fungicidal concentration value of 3.75 mg mL-1.
Conclusion: Pyrenacantha grandiflora contains substances that make it active against bacterial and fungal pathogens. This is the first time the antimicrobial and antifungal activities of P. grandiflora have been demonstrated scientifically. Extraction with hot water as done by the traditional healers showed activity thereby justifying the traditional use of this plant.
Keywords: Antibacterial; MFC; MIC; Pyrenacantha; antifungal; bacterial and fungal species.