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Two rare antioxidative prenylated terpenoids from loop-root Asiatic mangrove Rhizophora mucronata (Family Rhizophoraceae) and their activity against pro-inflammatory cyclooxygenases and lipoxidase
- Raola, Vamshi Krishna, Chakraborty, Kajal
- Natural product research 2017 v.31 no.4 pp. 418-427
- Rhizophora mucronata, antioxidant activity, inhibitory concentration 50, lipoxygenase, mass spectrometry, methanol, nuclear magnetic resonance spectroscopy, prostaglandin synthase, sesquiterpenoids, triterpenoids
- Two new biogenic prenylated terpenoids were isolated from the methanol extract of Rhizophora mucronata. The extended C ₂₀ sesquiterpenoid with prenylated guaiane framework was characterised as (4 E , 8 Z)-3, 3a, 6, 7-tetrahydro-3, 9-dimethyl-5-(6-methylheptan-2-yl) cycloocta[b]furan-2-(9aH)-one (1). (35 E)-1,2,3,5,6,6-icosahydro-4,4,8b,10,14,17,20,20-octamethylpicen-3-yl-34,35-dimethyloct-31-enoate (2) represents the first example of naturally occurring C ₄₀ prenylated oleanane-type triterpenoid, whereas one 4,5-dimethyloct-5-enoate side chain remains attached at C-3 position of the oleanane framework formed by the E-ring closure of C ₃₀ saccharide moiety. The structures of the compounds were elucidated using NMR and mass spectrometric analysis. Compound 1 was found to have significantly greater antioxidant activities (IC ₅₀ ~ 0.75 mg/mL) compared to 2 (IC ₅₀ > 0.80 mg/mL). No significant differences in anti-cyclooxygenase-2 of these compounds were discernable (IC ₅₀ 0.8 – 0.9 mg/mL), whilst compound 1 showed greater anti-5-lipoxidase activities (IC ₅₀ ~ 0.8 mg/mL) those that of 2 (IC ₅₀ 0.96 mg/mL). Bioactivities of the prenylated terpenoids were inversely proportional to lipophilic and bulk descriptors.