Evaluation of Antimicrobial Activities of Medicinal Plants Against Some Fungi and Antibiotic Resistant Bacteria

Abstract

ABSTRACT Bioactive chemicals from the medicinal plants are source of both traditional and modern medicines can be searched by ethno botanical approach or on the traditional knowledge of plants used. The secondary metabolites have the ability to kill microorganisms and have been used to cure diseases. The aim of the study is to evaluate the antimicrobial activities of some medicinal plants used in Ayurvedic medicine to treat gastrointestinal and dermatological diseases. Altogether, 16 plants belonging to 15 families were tested for their antimicrobial activities against 8 fungal and 15 bacterial strains. The plants were extracted in ethanol by percolation or soxhlet method. The percentage yield was the most in Centella asiatica (30.9%) and the least in Curculigo orchioides (6.8%). The antimicrobial susceptibility of selected clinical bacterial isolates was determined by modified Kirby-Bauer disk diffusion technique. The inhibitory effect was observed by agar cup-well method and minimum bactericidal concentration (MBC) by two fold serial broth dilution method. Fifteen plant extracts exhibited antifungal activity against at least one fungus. Acorus calamus exhibited the highest (6 out of 8) antifungal activity. Similarly 13 plant extracts exhibited the antibacterial activity against at least 5 bacteria. Cynodon dactylon exhibited the highest antibacterial activity (13 out of 15) in ethanolic extract. Then C. dactylon was extracted in solvents of increasing polarity into 4 fractions and the highest yield was in water (8.7%) and the lowest in chloroform (1.4%) fraction. Chloroform and n-butanol fraction exhibited better inhibitory effect than hexane and water. The highest zone of inhibition (ZOI) exhibited by Curcuma longa against Enterococcus faecalis (diameter 19 mm) and by A. calamus against Aspergillus niger (15 mm). Cinnamomum camphora gave the lowest value of minimum bactericidal concentration (MBC) (0.2 mg/ml) against S. pyogenes. Gram-negative bacteria were rather resistant; some plants (Adhatoda vesica and C. asiatica) did not exhibit any inhibitory effect against any Gram-negative bacteria. Only one plant extract exhibited inhibitory effect against Escehrichia coli (MDR), Salmonella enteritidis and Citrobacter freundii, however, these bacteria were resistant to the most of the common antibiotics. Some of the plant extracts exhibited substantial inhibitory effect against fungi and antibiotic resistant bacteria that could be used to treat for fungal and bacterial infection especially in dermatological and diarrheal diseases. Key words: Medicinal plants, Antibacterial activity, Antifungal activity, Multidrug resistance.