Evaluation of the antifungal and antibacterial activities of crude extracts of three species of Rigidoporus (Basidiomycota, Polyporaceae) from Cameroon

Abstract

This study aimed at assessing the antimicrobial activities of hexane and chloroform crude extracts of three species of Rigidoporus including R. microporus, R. ulmarius and R. vinctus on eleven strains of bacteria of which five gram-positive (Bacillus subtilis, Enterococcus faecalis, Staphylococcus epidermidis, Staphylococcus aureus, Mycobacterium smegmatis) and six gram-negative (Enterobacter cloacae, Proteus vulgaris, Klebsiella oxytoca, Klebsiella aerogenes, Proteus mirabilis, Escherichia coli), as well three species of human pathogenic fungi including Candida albicans, Aspergillus fumigatus and Aspergillus ochraceus. The assessment was done by determining the Minimal Inhibition Concentration (MIC). Results recorded globally show a strong activity of crude extracts on pathogenic fungi with MIC values ranging from 0.39 to 6.25 mg/mL. This activity was rather weak on all strains of bacteria tested with MIC values ranging from 6.25 to 12.5 mg/mL. More precisely, a strong activity (MIC = 0.39 mg/mL) of extracts of R. microporus and R. vinctus was recorded on Aspergillus fumigatus, a weak activity (MIC = 6.25 mg/mL) of R. ulmarius on the same Aspergillus species, and rather a strong activity (MIC = 0.39 mg/mL) of extracts of R. microporus and R. ulmarius on Aspergillus ochraceus. These results show that pathogenic fungi are generally much more sensitive to crude extracts of Rigidoporus than bacteria. Based on these preliminary and rather interesting results, it clearly appears that carpophores of these three species of Rigidoporus could constitute a source of new natural compounds that could be used to manufacture new pharmaceutical products potentially more efficient against some bacterial and fungal infections.