Anti-inflammatory xenicane-type diterpenoid from the intertidal brown seaweed Sargassum ilicifolium

Chemical analysis of the organic extract from intertidal brown seaweed Sargassum ilicifolium (family Sargassaceae) characterised an undescribed xenicane-type diterpenoid sargilicixenicane, elucidated as 3-(17-hydroxy-14-methylhept-13-en-10-yl)-6-methylhexahydro-1H-cyclonona[c]furan-4,19-diyl diacetate (compound 1). The studied compound exhibited prospective free radical quenching potential (IC₅₀ 1.2-1.4 mM) in comparison with commercial antioxidant (α-tocopherol, IC₅₀ > 1.40 mM). Attenuation property of sargilicixenicane against pro-inflammatory enzyme, 5-lipoxygenase (IC₅₀ 4.70 mM) was comparable with that displayed by the non-steroidal anti-inflammatory agent ibuprofen (IC₅₀ 4.51 mM). Greater selectivity index displayed by the studied xenicane-type diterpenoid (1.42) than that exhibited by ibuprofen (0.44) recognised the selective attenuation potential of the former against the inducible cyclooxygenase-2 and 5-lipoxygenase enzymes. Higher electronic parameters (topological polar surface area, 82.06) and balanced hydrophobic-hydrophilic property (octanol-water partition coefficient 2.94) coupled with docking score (-11.17 kcal mol^-1) and lower binding energy (-9.61 kcal mol^-1) with the active site of 5-lipoxygenase supported the significant anti-inflammatory properties of the studied xenicane-type diterpenoid.