Isosteviol

Isosteviol, a common natural sweetener, belongs to tetracyclic diterpene glycosides. The pharmacology researches have suggested that stevioside and its hydrolysis products, steviol, isosteviol and steviolbioside, have many biological activities, such as reducing blood glucose, lowering blood pressure, anti-inflammation, anti-tumor, anti-diarrhea, antibacterium, immunoregulation, etc. (In Vitro) :Isosteviol ((-) -Isosteviol) dose-dependently relaxed the vasopressin (10-8 M) -induced vasoconstriction in isolated aortic rings with or without endothelium. However, in the presence of potassium chloride (3x10-2 M), the vasodilator effect of isosteviol on arterial strips disappeared. Only the inhibitors specific for the ATP-sensitive potassium (KATP) channel or small conductance calcium-activated potassium (SKCa) channel inhibited the vasodilator effect of isosteviol in isolated aortic rings contracted with 10-8 M vasopressin.The attenuation by isosteviol of the vasopressin- and phenylephrine-induced increase in [Ca2+]i was inhibited by glibenclamide, apamin and 4-aminopyridine but not by charybdotoxin. Furthermore, the inhibitory action of isosteviol on [Ca 2+]i was blocked when A7r5 cells co-treated with glibenclamide and apamin in conjunction with 4-aminopyridine were present.Isosteviol (1-100 micromol/l) inhibits angiotensin-II-induced DNA synthesis and endothelin-1 secretion. Measurements of 2'7'-dichlorofluorescin diacetate, a redox-sensitive fluorescent dye, showed an isosteviol-mediated inhibition of intracellular reactive oxygen species generated by the effects of angiotensin II.