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Biogenic guaianolide-type sesquiterpene lactones with antioxidative and anti-inflammatory properties from natural mangrove hybrid Rhizophora annamalayana

Raola, Vamshi Krishna, Chakraborty, Kajal
Natural product research 2017 v.31 no.23 pp. 2719-2729
2,2-diphenyl-1-picrylhydrazyl, Rhizophora annamalayana, alpha-tocopherol, anti-inflammatory activity, antioxidant activity, chloroform, enzyme inhibition, hybrids, ibuprofen, inhibitory concentration 50, prostaglandin synthase, sesquiterpenoid lactones
Previously undescribed guaianolide-type sesquiterpene lactones were isolated from the chloroform fraction of the natural hybrid mangrove Rhizophora annamalayana , and were characterised as (Z)-3α,4,5,6-tetrahydro-5α-isobutyl-2β-(methoxymethyl)-7-methyl-3 H -cyclohepta[b]carbolactone (1) and (7 Z)-isopentyl 3α,4,5,6,7,8-hexahydro-2β-((E)-11-methylbut-10-enyl)-1-oxo-2 H -cyclohepta[b]furan-6-carboxylate (2). Compound 2 displayed greater antioxidative activities {1, 1-diphenyl-2-picrylhydrazyl (DPPH) and 2, 2′-azino-bis-3 ethylbenzothiozoline-6-sulphonic acid diammonium salt (ABTS), IC ₅₀ 0.65 and 0.62 mg/mL, respectively)} compared to 1 (IC ₅₀ 0.83 and 1.14 mg/mL, respectively) (p < 0.05). Compound 2 recorded no significant difference in DPPH . scavenging activities (IC ₅₀ 0.65 mg/mL) compared to α-tocopherol (IC ₅₀ 0.63 mg/mL). Pro-inflammatory 5-lipoxygenase inhibitory activity of 2 was found to be comparable (IC ₅₀ 0.98 mg/mL) to that displayed by synthetic anti-inflammatory drug ibuprofen (IC ₅₀ 0.93 mg/mL). Compound 2 showed significantly greater selectivity index (anti-cyclooxygenase-1/anti-cyclooxygenase-2 = 2.15) than non-steroidal anti-inflammatory ibuprofen (<0.5) (p < 0.05), and therefore, might be used as selective cyclooxygenase-2 inhibitor. The hitherto undescribed guaianolide lactones might be used as potential anti-inflammatory and antioxidative pharmacophore leads.