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Two previously undescribed furanyl compounds, characterized as 5-(7-(5-ethyl-3,4-dimethoxycyclooctyl) benzofuran-6-yl)-7-methyl-3,4,7,8-tetrahydro-2H-oxocin-2-one (compound 1) and 2-(3-ethyl-9-(2-methoxyethoxy)-1-oxo-2,3,4,9-tetrahydro-1H-xanthen-2-yl) ethyl-5-hydroxy-9-methoxy-7,8-dimethyl-8-(5-methylfuran-2-yl) nona-3,6-dienoate (compound 2) were derived from the ethyl acetate-methanol (EtOAc:MeOH) crude extract of red seaweed Gracilaria opuntia. The isolated compounds are the first furanyl natural products featuring methoxycyclooctyl benzofuran with tetrahydro-2H-oxocin framework and tetrahydro-1H-xanthenyl methoxy methylfuran skeletons. These compounds were assessed for anti-inflammatory activities against pro-inflammatory cyclooxygenase-2/5-lipoxygenase (COX-1, 2, and 5-LOX) and antioxidative effects in various in vitro models. The methylfuran derivative exhibited comparable inhibitory activities towards 5 LOX (IC50 0.209 × 10−2 M) with synthetic non-steroidal anti-inflammatory drugs (NSAID) ibuprofen (IC50 0.451 × 10−2 M, P < 0.05), which indicated its potential anti-inflammatory properties. The antioxidative properties of the furanyl derivatives as resolved by 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2ʹ-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid (ABTS) free radical scavenging activities were found to be significantly greater (IC50 ~0.051-0.055 × 10−2 M) than those exhibited by α-tocopherol (IC50 > 0.146 × 10−2 M), and were similar to those displayed by the synthetic antioxidants (butylated hydroxytoluene (BHT)/ butylated hydroxyanisole (BHA) (IC50 ~0.144-0.189 × 10−2 M, P < 0.05). The anti-inflammatory selectivity indices of the isolated compounds recorded significantly greater values (SI: anti-COX-1IC50/anti-COX-2IC50 ~1.08-1.09) than NSAIDs (aspirin, and ibuprofen, SI: 0.02 and 0.44, respectively, P < 0.05), and consequently, appeared to be safer. The isolated compounds showed significant anti-diabetic properties as determined by α-amylase/α-glucosidase (IC50 < 0.052 × 10−2 M) and dipeptidyl peptidase-4 (DPP-4, IC50 < 0.002 × 10−2 M) inhibitory activities. The angiotensin converting enzyme-I (ACE-I) inhibitory activity of the compounds (IC50 0.023-0.024 × 10−2 M) was found to be comparable with that recorded by commercial ACE inhibitor, captopril (IC50 0.037 × 10−2 M). [ABSTRACT FROM AUTHOR]

Previously undescribed chromenyl derivatives, characterized as 7-(2′-ethyl-1′-hydroxynonan-2′-yl)-6,7,8,8a-tetrahydro-3 H-isochromen-1-(5 H)-one ( 1) and 6-(3-(( E)-3-(furan-2′-yl)-prop-3-en-3-yl)-4a,5,6,8a-tetrahydro-8-methyl-2 H-chromen-6-yl)-ethyl-5′′-methyl-hexanoate ( 2) were isolated from ethyl acetate-methanol extract of yellow-foot bivalve clam, Paphia malabarica. Their structures have skeletons composed of isochromen-(5 H)-one and furanyl-2 H-chromenyl moieties, which are reported for the first time in marine organism. These were characterized by extensive one and two-dimensional nuclear magnetic resonance, infrared, and high-resolution mass spectroscopic experiments. The title compounds were evaluated for therapeutic potentials with regard to anti-inflammatory and antioxidant properties compared to known standards. These compounds exhibited comparable 2, 2-diphenyl-1-picrylhydrazyl (DPPH) and 2, 2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radical scavenging activities with α-tocopherol (IC ~0.6-0.7 mg/mL). The significantly higher anti-5-lipoxygenase activity of the title compounds (IC 0.76-0.82 mg/mL) than ibuprofen (IC 0.93 mg/mL) indicated their potential anti-inflammatory properties. The selectivity indices (IC anti-cyclooxygenase-1/ICanti-cyclooxygenase-2) of compounds 1 (1.19) and 2 (1.31) well established its safety profiles as an anti-inflammatory when compared to known drug, ibuprofen (0.44). The target bioactivities of chromenyl derivatives were guided by hydrophobic and electronic parameters. These compounds can be used as potential bioactive leads in functional food and medicinal applications. [ABSTRACT FROM AUTHOR]