Antibacterial activity of seven Indigenous Vegetables

Abstract

Aqueous, methanolic and ethanolic extracts of seven medicinal plant species commonly consumed in Thailand were evaluated for antimicrobial activity against four pathogenic bacteria, i.e. Escherichia coli ATCC25922, Klebsiella pneumoniae ATCC27736, Staphylococcus aureus ATCC6538 and Staphylococcus epidermidis ATCC12228, using the agar well diffusion method with 21 medicinal plant extract samples (30 μg/plate) for each bacterial strain. The results showed that the methanolic extract of Sechium edule caused the largest inhibition zones with E. coli and S. epidermidis of 20.46 mm and 35.23 mm in diameter, respectively; while the aqueous extract of Mentha cordifolia and the methanolic extract of Piper sarmentosum caused the largest inhibition zones with K. pneumoniae and S. aureus at 19.15 mm and 24.77 mm in diameter, respectively. The analysis of the minimum inhibitory concentration (MIC) which inhibited the four pathogenic bacteria using the microdilution assay showed that MICs of the methanolic extract of Sechium edule for E. coli and S. epidermidis were 7.81 mg/ml and 62.50 mg/ml, respectively, while the MIC of the aqueous extract of Mentha cordifolia and the methanolic extract of Piper sarmentosum for K. pneumoniae and S. aureus was 15.62 mg/ml. In addition, the MICs of chloramphenicol for E. coli, K. pneumoniae, S. epidermidis and S. aureus were 15, 7, 31 and 7 μg/ml, respectively.