Antimicrobial agents from Thai medicinal plants, Cleome viscosa Linn. and Gymnema griffithii Craib. fruits were investigated in this study. Leaves and stems, pods, roots and seeds of C. viscosa were collected from Nakornsawan and Ratchaburi and G. griffithii fruits were collected from Petchaburi. The hexane extract of pods, hexane extract of seeds and ethyl acetate of seeds from Nakornsawan showed antimicrobial activity at 50 μg/ml against Strephylococcus aureus with inhibition zones of 13, 11 and 9 mm, respectively. The hexane extract of pods from Nakornsawan and Ratchaburi also inhibited Propionibacterium acnes at 50 μg/ml with the inhibition zones of 15 and 13.5 mm, respectively.
After partition of methanol extract of G. griffithii fruits by dichloromethane. The dichloromethane extract and residue of G. griffithii were tested for antimicrobial activity. The results showed that the residue could inhibit P. acnes and E. coli at 100 µg/ml. But the dichloromethane extract could inhibit P. acnes at 50 µg/ml while inhibited E. coli at 100 µg/ml.
Isolation the antimicrobial compound from dichloromethane extract of G. griffithii fruits gave lupeol. Antimicrobial activity of lupeol was examined and it exhibited antimicrobial activity against E. coli and P. acnes with the minimum inhibition concentration (MIC) values of 25 and 50 μg/ml rescpectively.