Six new flavonoids—5-hydroxy-3,8-dimethoxy-3′,4′:6,7-bismethylenedioxyflavone (
1), 3,3′,4′,5-tetramethoxy-7-(3-methylbut-2-enyloxy)flavone (
2), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,3′,4′,5-tetramethoxyflavone (
3), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,5-dimethoxy-3′,4′-methylenedioxyflavone (
4), 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,3′,4′,5,8-pentamethoxyflavone (
5), and 7-(2-hydroxy-3-methylbut-3-enyloxy)-3,5,8-trimethoxy-3′,4′-methylenedioxyflavone (
6)—were isolated from the leaves of
Melicope triphylla. In addition, six already known flavonoids were also detected: 5-hydroxy-3,6,7-trimethoxy-3′,4′-methylenedioxyflavone (
7), 5,7-dihydroxy-3,3′,4′,8-tetramethoxyflavone (
8), 4′,5-dihydroxy-3,3′,7,8-tetramethoxyflavone (
9), 3,5,6,7,8-pentamethoxy-3′,4′-methylenedioxyflavone (
10), 3,5,6,7-tetramethoxy-3′,4′-methylenedioxyflavone (
11), and 3,3′,4′,5,6,7,8-heptamethoxyflavone (
12). The structures of the new compounds were established by spectroscopic methods. Compound
2 displayed ichthyotoxic activity against Japanese killifish (
medaka in Japanese) (
Oryzias latipes var.) at 10 ppm.
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