Benzoic acid derivatives, acetophenones, and anti-inflammatory constituents from Melicope semecarpifolia

Two new benzoic acid derivatives, (E)-3-acetyl-6-(3,7-dimethylocta-2,6- dienyloxy)-2,4-dihydroxybenzoic acid (1) and (E)-3-acetyl-4-(3,7-dimethylocta-2, 6-dienyloxy)-2,6-dihydroxybenzoic acid (2), and three new acetophenones, (E)-1-(5-(3,7-dimemylocta-2,6-dienyloxy)-7-hydroxy-2,2-dimemyl-2H-chromen-8-yl) ethanone (3), (E)-1-(5-(3,7-dimethylocta-2,6-dienyloxy)-7-hydroxy-2-methyl-2-(4- methylpent-3-enyl)-2H-chromen-8-yl)ethanone (4), and (R,E)-1-(5-(3,7- dimethylocta-2,6-dienyloxy)-3,7-dihydroxy-2,2-dimethylchroman-8-yl)ethanone (5), have been isolated from the fruits of Melicope semecarpifolia, together with eight known compounds. The structures were determined through in-depth NMR and mass spectrometric analyses. Among the isolated compounds, 2-(1′- geranyloxy)-4,6,β-trihydroxyacetophenone (8), 4-(1′-geranyloxy)-2,6, β-trihydroxyacetophenone (9), 5-hydroxy-3,7,3′,4′- tetramethoxyflavone (10), 5,4′-dihydroxy-3,7,3′-trimethoxyflavone (11), and 5,4′-dihydroxy-3,7-dimethoxyflavone (12) exhibited potent inhibition (IC₅₀ < 4 μg/mL) on superoxide anion generation and elastase release by human neutrophils in response to fMet-Leu-Phe/cytochalasin B.