Triterpenoid, lup-1, 2-ene-3-one (1), lupeol (2), oleanolic acid (3), ursolic acid (4) and steroid, â-sitosterol (5) was isolated from the toluene extract of the root of Croton bonplandianum Bail. Their chemical structures were established on the basis of spectroscopic analysis (UV, IR, NMR, Mass etc.) and by chemical means. A probable biosynthetic pathway of compound 1 was also proposed. Compound 1 and 2 is reporting first time to obtain from this plant. The triterpenpoids (1, 2, 3 and 4) have also been screened for their antimicrobial activity. Preliminary investigation showed potent activity of 1against a series of fungal and bacterial pathogens.