Antibacterial, antioxidant and anticancer activities of biphenyls from Streptomyces sp BO-07: an endophyte in Boesenbergia rotunda (L.) Mansf A.

Strain BO-07 was isolated from the root tissue of Boesenbergia rotunda (L.) Mansf A. and identified as Streptomyces sp. on the basis of morphology, chemotaxonomy and 16S rDNA sequencing. The fractionation of the crude extract from strain BO-07 cultures led to the isolation of two biphenyls: 3'-hydroxy-5-methoxy-3,4-methylenedioxybiphenyl (1) and 3'-hydroxy-5,5'-dimethoxy-3,4-methylenedioxybiphenyl (2); these compounds and the crude extract had potent antibacterial activity against Gram-positive bacteria, and antioxidant and anticancer activities. These compounds showed the highest activity against Staphylococcus aureus ATCC25932, Bacillus cereus ATCC7064 and Bacillus subtilis ATCC6633 with a minimum inhibitory concentration value of 0.5 mu g/ml and minimum bactericidal concentrationof 2-8 mu g/ml. Compounds 1 and 2 showed the highest (1, 1diphenyl-2-picryl hydrazyl)DPPH antioxidant activity with a scavenging concentration (SC50) value of 85.84 and 88.26 mu g/ml, respectively, and also showed strong cytotoxicity against all the three cancer cell lines (HeLa, HepG2 and Huh7) at an IC50 value of 3.04-20.30 mu g/ml. Both the compounds were less toxic on normal cells (L929) than on the investigated cancer cell lines.