Studies on bioactive constituents from the leaves of Zanthoxylum avicennae

Zanthoxylum avicennae (Lam.) DC (Rutaceae) is an evergreen shrub distributed in Vietnam, Philippines, southern China, and Taiwan. Z. avicennae, locally called 'Ying Bu Bo', is used as a folk medicine for treatment of rheumatism, abdominal pain, jaundice, chronic hepatitis, and common cold in China. In our studies on the anti-inflammatory constituents of Formosan plants, many species have been screened for in vitro inhibitory activity on neutrophil pro-inflammatory responses, and Z. avicennae has been found to be an active species. Investigation on EtOAc-soluble fraction of the leaves of Z. avicennae has led to the isolation of four new coumarins, 5'-methoxy- collinin (1), 5'-methoxyauraptene (2), 7-((2'E,5'E)-7'-methoxy-3',7'-dimethylocta-2',5'-dienyloxy)coumarin (3), 6-methoxy-7-((2'E,5'E)-7'-methoxy-3',7'-dimethylocta-2',5'- dienyloxy)coumarin (4), along with 16 known compounds (5–20). Compounds 8, 13–15, 18, and 19 exhibited inhibition (IC₅₀ ≤ 7.67 µg/ml) of superoxide anion generation by human neutrophils in response to formyl-L-methionyl-L-leucyl-L-phenylalanine/cytochalasin B (fMLP/CB). Compounds 8, 14, and 18 inhibited fMLP/CB-induced elastase release with IC₅₀ values ≤ 6.30 µg/ml.