Antimicrobial activities of creams prepared with methanol and aqueous leaf extracts of Ricinus communis L. (Euphorbiaceae)

Abstract

The aqueous and methanol crude extracts of the leaves of Ricinus communis L. (Euphorbiaceae) have been reported to possess antimicrobial activity. This study was carried out to investigate the antimicrobial activity of the cream formulations of these leaf extracts against some pathogens. The extract of R. communis was obtained by maceration of the blended leaf using methanol or distilled water. Topical creams were prepared by mixing 6 g of cetomacrogol ointment BP with an aqueous phase prepared by dispersing 4 g of the extract in 10 mL of purified water. Agar well diffusion method was used to determine the antimicrobial activity of the creams against test organisms using diameter of zones of inhibition as a measure of activity. Plain creams formulated and a commercial antimicrobial cream were also tested. The yield of the extraction was 7.27 and 6.73 % with methanol and water respectively. Extracts were dark green in colour with a pungent odour. The colours of the creams formulated were also dark green while their pH values range from 2.54-5.01. Diameter of zones of inhibition produced against gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and gram-negative bacterium (Pseudomonas aeruginosa) were 26, 18 and 14 mm for the methanol extract and 16, 13 and 11 mm for the aqueous extract. Escherichia coli and Candida spps were not inhibited by both extracts. The antimicrobial microbial activity of the methanol extract cream was comparable to that of the commercial cream. The plain creams showed no antimicrobial effect on all test organisms. The creams of methanol and aqueous extract of R. communis L. leaf have significant antimicrobial activity against test organisms except E. coli and Candida spps. The methanol extract cream would be useful in skin infections where the pathogen S. aureus is implicated.

Keywords:  Ricinus communis, zones of inhibition, cetomacrogol emulsifying ointment BP, maceration