New sterols with anti-inflammatory potentials against cyclooxygenase-2 and 5-lipoxygenase from Paphia malabarica

Abstract

Marine bivalves occupy a leading share in the total edible molluscs at the coastline regions of south-eastern Asia, and are found to possess significant nutritional and biological potential. Various in vitro evaluation (antioxidant and anti-inflammatory) guided purification of ethyl acetate–methanol (EtOAc–MeOH) extract of bivalve clam, Paphia malabarica characterised two new sterol derivatives as 23-gem-dimethylcholesta-5-en-3β-ol (1) and (22E)-24¹,24²-methyldihomocholest-5,22-dien-3β-ol (2) collected from the south-west coast of Arabian Sea. Their structures were unambiguously assigned on the basis of 1D, 2D NMR spectroscopy and mass spectrometry. The antioxidant and anti-inflammatory activities of 2 as determined by DPPH/ABTS⁺ radical scavenging and anti-cyclooxygenase-2/5-lipoxygenase assays were significantly greater (IC₅₀ < 1 mg/mL) than 1 (IC₅₀ > 1 mg/mL). Structure–activity relationship analysis revealed that the bioactivities of these compounds were directly proportional to the electronic and lipophilic parameters. This is the first report of the occurrence and characterisation of 23-gem-dimethyl-3β-hydroxy-Δ⁵-cholestane nucleus and C-30 dihomosterol from marine organisms.

Keywords:

• Bivalve clam
• Paphia malabarica
• 23-gem-dimethylcholesta-5-en-3β-ol
• (22E)-24¹,24²-methyldihomocholest-5,22-dien-3β-ol
• anti-inflammatory activity

Acknowledgements

The authors thank the Director, Central Marine Fisheries Research Institute for valuable guidance and support. Thanks are due to the Head, Marine Biotechnology Division, Central Marine Fisheries Research Institute for facilitating the research activity. M.J. and V.R. acknowledge Indian Council of Agricultural Research for fellowships.