A new isoflavanone namely 3,5,7,2',4'-pentahydroxy-8,3'-di(gamma,gamma-dimethylallyl)isoflavanone (bolusanthin II) and four new pterocarpans identified as 3-hydroxy-6',6'-dimethylpyrano[2',3':1,2] [6a R,11a R]-8,9-methylenedioxypterocarpan (bolucarpan A), 3-hydroxy-6',6'-dimethyl-4',5'-dihydropyrano[2',3':1,2][6a R,11a R]- 8,9-methylenedioxypterocarpan (bolucarpan B), 3-hydroxy-9-methoxy-6',6'-dimethylpyrano-[2',3':1,2][6a R,11a R]-pterocarpan (bolucarpan C) and 3-hydroxy-9-methoxy-6',6'-dimethyl-4',5'-dihydropyrano[2',3':1,2][6a R,11a R]-pterocarpan (bolucarpan D) and three known isoflavonoids were isolated from the methanolic extracts of the root bark, while eight known isoflavonoids were isolated from the stem bark of Bolusanthus speciosus. These compounds showed antimicrobial activity against Bacillus subtilis, Staphylococcus aureus, Escherichia coli, Saccharomyces cerevisiae and Candida mycoderma using the agar overlay technique.