10.22376/ijpbs.2019.10.1.p1-12 Volume 5 Issue 2 2014 (April - June) The purpose of present work is to study antimicrobial activity and medicinally active principles present in different solvent extracts obtained from roots of Heracleum rigens. The active principles were isolated by Soxhlet extractor using petroleum ether, chloroform, ethyl acetate and methanol and identified by preliminary phytochemical test. The results of analyses of each extract confirm the active substances were alkaloids, sterols, triterpenes, glycosides and flavonoids. The antimicrobial tests of isolated substances were performed against bacteria- Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Pseudomons aeruginosa, and a fungus Candida albicans. The results revealed that ethyl acetate extract has significant antimicrobial activities. Heracleum rigens revealed the highest antibacterial activity at a minimum inhibitory concentration (6.25µg/ml) against P.aeruginosa and highest antifungal activity at a MIC (1.56µg/ml) against C.albicans. The results provide justification for the use of the H.rigens in folk medicine to treat various infectious diseases.  LINGARAJU D P AND SUDARSHANA M S Heracleum rigens, Phytochemical screening, Secondary metabolites, Antibacterial activity, Antifungal activity. 288-294