New bioactive compounds of plant origin

Crude extracts of Withania somnifera (WS) and Polygonum equisetiforme (PE) as well as the pure compounds isolated therefrom were screened for antibacterial and antifungal activity against 20 bacterial and 17 fungal cultures. The crude extract of PE and WS inhibited the growth of T. mentagrophyte, M. canis and A. boydii at an MIC of 450-500 microg/ml whereas the pure compounds inhibited the growth at MIC of 300-350 micro/ml. Species of Corynebacterium, Bacillus, Streptococcus and Staphylococcus were found to be highly susceptible to both the crude sad the pure compounds. MIC values of both crude extracts for different organisms tested were found to be higher (200-350 microg/ml) than the pure compounds (150-170 microg/ml). The crude extract of PE did not inhibit the growth of Ps. aeruginosa, however, the pure compound was found to be bacteriostatic. Brine shrimp and BALB/c mice lethality test indicated that these extracts maybe toxic at high concentration.