Characterization and bioactive potentials of secondary metabolites from mollusks <i>Crassostrea madrasensis</i> and <i>Amphioctopus marginatus</i>

<p>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 (<b>1</b>) and methyl-3-(26-phenylacetyloxy)-icosahydro-1,19-dihydroxy-4,4,20-trimethylpicene-23-carboxylate (<b>2</b>) from <i>Crassostrea madrasensis</i>, whereas cholesta-5-en-3<i>β</i>-yl-(32-methyl-(30-((<i>E</i>)-34-amino-36-ethyl-39-oxohept-36-enyl)-pentanedioate (<b>3</b>) and 7-ethyl-9-vinyl-octahydroazuleno [1,8-<i>bc</i>]pyran-3,12-dione (<b>4</b>) were isolated from <i>Amphioctopus marginatus</i>. Their structures were assigned by detailed spectroscopic experiments. The studied compounds were checked for antioxidant and anti-inflammatory activities by various <i>in vitro</i> 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 <b>2</b> (IC₅₀ 0.85 and 1.10 mg/mL, respectively) than other studied compounds. The pro-inflammatory cyclooxygenase-2 inhibitory activity of <b>2</b> was greater (IC₅₀ 0.95 mg/mL) than those displayed by other studied compounds (>1.0 mg/mL). The 5-lipoxygenase inhibitory potential of <b>1</b> and <b>2</b> (~1.36 mg/mL) were greater than those displayed by <b>3</b> (1.64 mg/mL) and <b>4</b> (1.45 mg/mL).