INTRODUCTION

Antibiotic resistance is one of the greatest threats of the 21 century. Scientists search for potential antimicrobial sources that can cope with antibiotic resistance. Plants used in traditional medicine can be identified as potential candidates for the synthesis of novel drug compounds to act against antibiotic-resistant bacteria.

OBJECTIVE

To determine the potential antimicrobial effects of ethanol, aqueous, and hexane extracts of five Sri Lankan medicinal plants against four human pathogens.

METHODS

(tubers), (whole plant), (roots), (whole plant), and (seeds) were used in the study. Plant extracts were screened against four clinically important Gram-positive and Gram-negative bacterial strains, (ATCC 25923), (ATCC 25922), (ATCC 27853), and (ATCC 700603). Antibacterial activity of plant extracts were monitored using the agar disc diffusion method. Eight concentrations of each positive plant extract were used to determine the minimum inhibitory concentration (MIC) by 5-fold dilution of plant extracts yielding a serial dilution of the original extract.

RESULTS

Ethanol, aqueous, and hexane extracts of gave the maximum zones of inhibition of 16.3 mm, 7.4 mm, and 13.7 mm and MIC values of 0.48 mg/ml, 1.2 mg/ml, and 1.6 mg/ml, respectively, against . Ethanol and hexane extracts of gave the maximum zones of inhibition of 12.1 mm and 11.4 mm and MIC values 2.4 mg/ml and 0.003 mg/ml, respectively, against . None of the other plants were effective against any microorganism used for the study.

CONCLUSIONS

It can be concluded that and crude ethanol, aqueous, and hexane extracts exhibited significant antibacterial activity against , and the active compounds isolated from them can be potential sources for the synthesis of antibacterial drugs.