薬理と治療

Abstract

Objectives　In humans, the antihypertensive effect of geniposidic acid via atrial natriuretic peptide（ANP）secretion is observed in Eucommia bark extract in which cyclic AMP phosphodiesterase（ cAMP-PDE）inhibitor coexists. On the other hand, the antihypertensive effect of geniposidic acid via ANP secretion is not observed in Eucommia leaf extract in which cAMP-PDE inhibitor does not coexist. 　For a long time（almost 20 years or more）, it has been believed that the antihypertensive effect of Eucommia leaf extract depends on the direct action of geniposidic acid to the parasymphasic nervous system, which results in the release of nitric oxide（NO）from the vascular endothelial cells, followed by the relaxation of vascular smooth muscle. However this mechanism is not correct since geniposidic acid does not act on the muscarinic acetylcholine receptor. 　The antihypertensive effect of Eucommia leaf extract in humans was considered from our previous and other reports. Methods　In order to determine the active ingredient in Eucommia leaf extract, each of the contents of iridoid compounds, phenolic compound and flavonoid compounds was measured by using the HPLC-UV method in the comparison with 85.0 mg of geniposidic acid（indicator component）in Eucommia leaf extract. Results　Geniposidic acid itself was also estimated to be the active ingredient showing the antihypertentive effect without the coexistence of cAMP-PDE inhibitor. Conclutions　Geniposidic acid is reported as a TNFα inhibitor. Therefore, it was suggested that the antihypertensive effect of the Eucommia leaf extract in humans might be dependent on the improvement of the vascular endothelial function by the suppression of the inflammation of blood vessels caused by TNFα. （Jpn Pharmacol Ther 2022；50：1013‒21）