ANTIMICROBIAL EFFECTS OF Richardia brasiliensis GOMES CRUDE EXTRACTS

Abstract

Dried leaf powder of Richardia brasiliensis was extracted separately with ethanol and water using maceration method. Phytochemical components of the extracts were analyzed using standard conventional protocols and the extracts were serially diluted to get extract - water ratio of 0:1 (control), 1:2, 1:4, 1:6, and 1:8. Clinical strains of Staphylococcus aureus and Pseudomonas aeruginosa and Laboratory strains of Aspergillus niger and Penicillium notatum were tested against the extracts, using the paper disc diffusion method. Discs containing gentamycin (10 ?g/ml) and griseofulvin (10 ?g/ml) instead of plant extract served as positive controls, for bacteria and fungi, respectively, while discs with distilled water only, served as negative controls. Potato Dextrose Agar (for fungi) and Nutrient Agar (for bacteria) culture plates were incubated at 25 oC and 37 oC for 48 and 24 hours, respectively. Phytochemical analysis showed the presence of alkaloids, flavonoids, tannins, saponins and terpenoids. Both ethanol and water extracts showed inhibitory activity against bacteria and fungi. The 1:2 dilution had the greatest effect (diameter = 22 mm for S. aureus and 21 mm for P. aeruginosa for ethanol extract while S. aureus had 12 mm and P. aeruginosa 15 mm. For A. niger, 15.6 mm (ethanol) and 13.5 mm (water) were recorded whereas P. notatum had 15 mm (ethanol) and 13.1 mm (water). The 1:8 dilution produced the least effect in both bacteria and fungi. Results for control (gentamycin) compared well (no significant difference) with those for ethanol extract treatments at the 1:2 dilution (P = 0.05). Griseofulvin gave values that were not significantly different from results of ethanol extract treatments at 1:2 dilution.