Isolation, structure elucidation and bioactivity of secondary metabolites produced by marine derived Streptomonospora arabica VSM-25

Abstract

The strain VSM-25 with an exhilarating bioactive potential isolated during our systematic screening of marine actinomycetes was identified as Streptomonospora arabica based on polyphasic taxonomy. The ethyl acetate extract of culture filtrate was purified by silica gel column chromatography. The chemical structure of active compounds was determined by NMR, FTIR, and ESIMS and were established as Indole-3-carboxaldehyde (C1), 2, 3-dihydroxy benzoic acid (C2), Vanillic acid (C3), Daidzein (C4), and 3, 4-Dihydroxy benzaldehyde (C5). The antimicrobial activities of the compounds were tested against medicinally and agriculturally significant bacteria and fungi. C1 displayed a high inhibitory effect against bacteria and fungi to that of the other compounds tested. C5 exerted the strongest scavenging activity of free radicals such as DPPH and NO at a concentration of 400 µg/mL. C1 inhibited alpha-amylase effectively at 400 µg/mL although it was less potent than acarbose. C3 and C4 exerted significant anti-inflammatory and anti-arthritic activities at 400 µg/mL. The anti-inflammatory activity of compound C3 was found to be more potent than Diclofenac sodium, the reference drug. MTT assays of five compounds against MDA-MB-231 and MCF-7 cell lines using taxol as standard documented cytotoxicity. C4 showed highest activity of 67.81% and 54.33% (IC50 -1 µg/mL) against MDA-MB-231 and MCF-7. The cytotoxicity of five compounds was also evaluated by soft agar colony forming assay to determine the ability of MDA-MB-231 cells to proliferate while cell cycle arrest at sub G1 and induction of apoptosis was documented with MDA-MB-231 cells after treatment with C1, C2, C3, C4, and C5.