Flavonoids from Dalbergia louvelii and their antiplasmodial activity.

Four new flavonoids (1-4), along with 13 known compounds, were isolated from the heartwood of Dalbergia louvelii by following their potential to inhibit in vitro the growth of Plasmodium falciparum. Of the isolated compounds, four known compounds showed antiplasmodial activity with IC(50) values ranging from 5.8 to 8.7 microM, namely, (R)-4' '-methoxydalbergione (5), obtusafuran (6), 7,4'-dihydroxy-3'-methoxyisoflavone (7), and isoliquiritigenin (8). The structures of the new compounds were determined using spectroscopic techniques as 1-(3-hydroxyphenyl)-3-(4-hydroxy-2,5-dimethoxyphenyl)propane (1), spirolouveline (2), (3R)-7,2'-dihydroxy-4',5'-dimethoxyisoflavanone (3), and 3-(2,4-dihydroxy-5-methoxy)phenyl-7-hydroxycoumarin (4), respectively.