Inhibition of angiotensin converting enzyme (ACE) by flavonoids isolated from Ailanthus excelsa (Roxb) (Simaroubaceae).

In our screening program for antihypertensive properties of plants, the leaves of Ailanthus excelsa (Roxb), a plant used in Egyptian traditional medicine, were analysed. Chromatographic separation of A. excelsa MeOH extract yielded six flavonoids for the first time from this species, namely apigenin, luteolin, kaempferol-3-O-alpha-arabinopyranoside, kaempferol-3-O-beta-galactopyranoside, quercetin-3-O-alpha-arabinopyranoside and luteolin-7-O-beta-glucopyranoside. The in vitro hypotensive activities of the MeOH extract and the isolated compounds were elucidated. All the flavonoids tested exhibited ACE inhibitory activity, in particular the most active compound was kaempferol-3-O-beta-galactopyranoside with an IC(50) value of 260 microm.