Comparative vasodilating actions among terpenoids and flavonoids contained in Ginkgo biloba extract

Background: Comparative vasodilating actions of the constituents of Ginkgo biloba extract (GBE), terpenoids (bilobalide, ginkgolides A, B and C) and flavonoids (quercetin and rutin), were examined using rat aorta ring strips. Methods: Cumulative administrations of GBE and its constituents were followed with the pretreatment of 5 mumol/l NE. Results: GBE at 0.03 to 3 mg/ml had a potent concentration-dependent relaxation; by 70 +/- 4.5% (n = 6, P < 0.001) at 3 mg/ml. Terpenoids and flavonoids at 0.1 to 100 mumol/l had potent concentration-dependent relaxation. At 100 mumol/l, bilobalide dilated by 17.6 +/- 3.9% (n = 7, P < 0.05), and ginkgolides A, B and C also caused it to the almost same extent. Quercetin (100 mumol/l) caused a potent vasorelaxation by 49.9 +/- 4.8% (n = 10, P < 0.001). Rutin at 100 mumol/l had weaker vasorelaxation; by 13.7 +/- 3.2% (n = 6, P < 0.01). Conclusions: All constituents of GBE have the concentration-dependent vasorelaxtant effect. The potency of GBE's action was not made simply by addition of those of the constituents. Each constituent itself would contribute to the GBE-induced vasodilation, although the constituents have the complicated interactions with each other. (C) 2003 Elsevier B.V. All rights reserved.