First report of substituted 2 H- pyranoids from brown seaweed Turbinaria conoides with antioxidant and anti-inflammatory activities.

The organic extract of Turbinaria conoides , a brown seaweed harvested from the Gulf of Manner region of Indian peninsular was chromatographically fractionated to yield three substituted 2 H- pyranoids, namely methyl-2 ¹ -yl-[5', 6'- dihydro-5'-yl-{5 ⁴ -(4-hydroxybenzoyl)-oxy-(5 ² -methylbutyl)}-3'-methyl-2 H -pyran]-2 ¹ -methyl butanoate ( 1 ), 11-[(3', 6'-dihydro-4'-methyl-2'-oxo-2 H -pyran-3'-yl)methyl]-10-methylhexyl benzoate ( 2 ), and [6-ethyl-3,4-dimethyl-(tetrahydro-2', 2', 6'-trimethyl-2 H -pyran-3'-yl)-2,5-cycloheptadiene]-1-propanoate ( 3 ). The compounds 1 and 2 bearing 2 H -pyranyl-4-hydroxybenzoyl and 2 H -pyranyl-10-methylhexylbenzoate moieties exhibited potential antioxidant activities (IC ₅₀ 0.54-0.69 mg mL ^-1 ) as commercial antioxidant ( α -tocopherol IC ₅₀ 0.63-0.73 mg mL ^-1 ). Likewise, potential bioactivity of the 2 H -pyran derivative, 1 against 5-lipoxygenase (IC ₅₀ ∼ 1 mg mL ^-1 ) along with higher index of selectivity (COX-1 inhibitory _IC50 /COX-2 inhibitory _IC50 1.88) indicated their selective anti-inflammatory properties against inducible inflammatory mediators than that displayed by commercially available non-steroidal anti-inflammatory drug (ibuprofen, 0.44). Structure activity relationship analysis of the studied compounds showed that the antioxidative and anti-inflammatory properties were directly proportional to their electronic properties. The previously undescribed 2H- pyranoids might constitute as potential antioxidative and anti-inflammatory pharmacophores for medicinal applications. [Formula: see text].