Asian Journal
Of Traditional Medicines

Abstract: The effects of Ginkgo biloba (Ginkgoaceae), its terpene-lactones (ginkgolide A, B, C and bilobalide), biflavonols (quercetin), biflavones (sciadopitysin) and proanthocyanidins (procyanidin) on angiotensin-converting enzyme (ACE) activity and nitric oxide (NO) production in cultured human endothelial cells from umbilical veins (HUVEC) were investigated. A dose-dependent significant inhibition of the ACE activity was observed after 10 min incubation with Ginkgo biloba extract EGb 761 and quercetin. No significant effects due to terpene-lactones or sciadopitysin were seen. Incubation with Ginkgo biloba extract, quercetin, sciadoitysin and procyanidin for 24 hr significantly increased NO production. No significant effects were seen with ginkgolide A, B and C, while bilobalide induced a dose-dependent decrease in NO production. In conclusion, this study shows that Ginkgo biloba extract inhibits ACE activity and increases NO production from HUVEC. A flavonol (quercetin and/or homologs) is the main component responsible for the inhibitory effect of ACE activity. Quercetin and a proanthocyandin (procyanidin) are responsible for the increases seen in NO production. These results may explain the positive effects of Ginkgo biloba on the cardiovascular system and on cognitive function.

Key words: angiotensin-converting enzyme, flavonoids, Ginkgo biloba, nitric oxide, terpene-lactones