Characterization and bioactive potentials of secondary metabolites from mollusks Crassostrea madrasensis and Amphioctopus marginatus.

Chemical investigations of the ethyl acetate-methanol (EtOAc-MeOH) extract of the selected mollusks from the south-west coast of Arabian Sea led to the isolation of methyl-3-(26-phenylacetyloxy)-icosahydro-19-hydroxy-4,4,20-trimethylpicene-23-carboxylate (1) and methyl-3-(26-phenylacetyloxy)-icosahydro-1,19-dihydroxy-4,4,20-trimethylpicene-23-carboxylate (2) from Crassostrea madrasensis, whereas cholesta-5-en-3β-yl-(32-methyl-(30-((E)-34-amino-36-ethyl-39-oxohept-36-enyl)-pentanedioate (3) and 7-ethyl-9-vinyl-octahydroazuleno [1,8-bc]pyran-3,12-dione (4) were isolated from Amphioctopus marginatus. Their structures were assigned by detailed spectroscopic experiments. The studied compounds were checked for antioxidant and anti-inflammatory activities by various in vitro experiments. The radical quenching potential of 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azino-bis-3-ethylbenzothiozoline-6-sulfonic acid diammonium salt were greater for 2 (IC50 0.85 and 1.10 mg/mL, respectively) than other studied compounds. The pro-inflammatory cyclooxygenase-2 inhibitory activity of 2 was greater (IC50 0.95 mg/mL) than those displayed by other studied compounds (>1.0 mg/mL). The 5-lipoxygenase inhibitory potential of 1 and 2 (~1.36 mg/mL) were greater than those displayed by 3 (1.64 mg/mL) and 4 (1.45 mg/mL).