First report of antioxidant abeo-labdane type diterpenoid from intertidal red seaweed Gracilaria salicornia with 5-lipoxygenase inhibitory potential

Phytochemical investigation on the biologically active compounds of seaweed Gracilaria salicornia {(C. Agardh) E.Y. Dawson} (family Gracilariaceae) guided to the separation of a previously unreported abeo-labdane class of diterpenoid. The compound was characterized as methyl-16(13 -> 14)-abeo-7-labdene-(12-oxo) carboxylate by extensive spectroscopic experiments, and comparison with the related compounds. The studied compound registered significantly greater activities against pro-inflammatory 5-lipoxygenase (IC50 0.86 mg/mL) than that exhibited by non-steroidal anti-inflammatory agent ibuprofen (IC50 0.92 mg/mL, P < 0.05). Likewise, this compound exhibited comparable radical quenching (1, 1-diphenyl-2-picryl-hydrazil) activity (IC50 0.66 mg/mL) as standard antioxidant agent alpha-tocopherol (IC50 0.62 mg/mL).