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

Abstract

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 2H-pyranoids, namely methyl-2¹-yl-[5′, 6′- dihydro-5′-yl-{5⁴-(4-hydroxybenzoyl)-oxy-(5²-methylbutyl)}-3′-methyl-2H-pyran]-2¹-methyl butanoate (1), 11-[(3′, 6′-dihydro-4′-methyl-2′-oxo-2H-pyran-3′-yl)methyl]-10-methylhexyl benzoate (2), and [6-ethyl-3,4-dimethyl-(tetrahydro-2′, 2′, 6′-trimethyl-2H-pyran-3′-yl)-2,5-cycloheptadiene]-1-propanoate (3). The compounds 1 and 2 bearing 2H-pyranyl-4-hydroxybenzoyl and 2H-pyranyl-10-methylhexylbenzoate moieties exhibited potential antioxidant activities (IC₅₀ 0.54-0.69 mg mL⁻¹) as commercial antioxidant (α-tocopherol IC₅₀ 0.63-0.73 mg mL⁻¹). Likewise, potential bioactivity of the 2H-pyran derivative, 1 against 5-lipoxygenase (IC₅₀ ∼ 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.

Keywords:

• Turbinaria conoides
• substituted pyran derivatives
• 2H-pyranoids
• anti-inflammatory
• pro-inflammatory cyclooxygenase and lipoxygenase

Acknowledgements

The work was supported by Science and Engineering Research Board (SERB) (grant number SR/S1/OC-96A/2012) of the Department of Science and Technology, New Delhi, India. The authors thank the Director, Indian Council of Agricultural Research-Central Marine Fisheries Research Institute (ICAR-CMFRI), and Head, Marine Biotechnology Division, ICAR-CMFRI for guidance and support.

Disclosure statement

The authors report no conflict of interest.