Abstract

ASSESSMENT OF ANTIBACTERIAL AND ANTIFUNGAL ACTIVITIES OF THE EXTRACTS OF RHYNCHOSTYLIS RETUSA BLUME- A MEDICINAL ORCHID

Bakul Bhattacharjee and S. M. Shahinul Islam*

ABSTRACT

Rhynchostylis retusa is a monopodial, epiphytic and medicinal orchid. The phytochemical screening and antimicrobial activities of different extract (methanol, ethanol, chloroform and hexane) of Rhynchostylis retusa was applied on five different bacteria (gram positive: Staphylococcus aureus & Bacillus subtilis; gram negative: Vibrio cholerae, Escherichia coli & Klebsiella pneumonia) and three fungus species (Penicillium sp., Rhizopus sp. and Aspergillus niger). The antmicrobial activity was assessed using disc diffusion method. A preliminary phytochemical screening was performed on the basis of detection of alkaloid, terpenoids, flavonoids, tannins, steroids, coumerins, amino acides and carbohydrates. Under this study methanol, ethanol and chloroform extracts from Rhynchostylis retusashowed different degree of inhibitory that potential against tested bacteria while hexane extract not showed any inhibition zone on studied bacteria. The antibacterial activity against all bacteria with the zone of inhibition ranging from 5‐12 mm were observed and found that highest inhibition zone (10-12 mm) with the concentration of 10.0 mg/ml of chloroform extract. Chloroform extract also showed significant antifungal activity against Penicillium, Rhizopus and Aspergillus niger with the highest zone (12‐15 mm) of inhibition. The ability of the crude extracts of Rhynchostylis retusa to inhibit the growth of bacteria and fungus is an indication of its broad spectrum antimicrobial potential which may be employed in the management of microbial infections.

Keywords: Rhynchostylis retusa, phytochemical, antimicrobial, disc diffusion method.