Piceatannol 3'-O-glucoside, an active component of Rhubarb, activates endothelial nitric oxide (NO) synthase through inhibition of arginase activity with IC50s of 11.22 µM and 11.06 µM against arginase I and arginase II, respectively. NO synthase[1]IC50: 11.22 μM (Arginase I), 11.06 μM (Arginase II)[1]

Piceatannol 3'-O-glucoside (Piceatannol-3'-O-β-D-glucopyranoside; PG) is a potent component of stilbenes, inhibits the activity of arginase I and II prepared from mouse liver and kidney lysates, respectively, in a dose-dependent manner. In human umbilical vein endothelial cells, incubation of Piceatannol 3'-O-glucoside markedly blocks arginase activity and increases nitrite and nitrate (NOx) production, as measured by Griess assay. In liver lysates, incubation of different concentrations of Piceatannol 3'-O-glucoside significantly decreases arginase I activity (75±5% at 1 µM, 72±7% at 3 µM, 62±1% at 10 µM) compared to untreated control (100±9%). In kidney lysates, the residual arginase activities after incubation of 1, 3 and 10 µM Piceatannol 3'-O-glucoside are 75±6, 74±5, and 53±8%, respectively. Arginase activity is measured in the presence of different concentration of Piceatannol 3'-O-glucoside (from 0 to 120 µM) using liver lysate and kidney lysate. The 50% inhibitory concentrations (IC50) are 11.22 µM for the liver lysate and 11.06 µM for kidney lysate. The values are obtained using the software of Graphpad prizm 4.0. Piceatannol 3'-O-glucoside inhibits arginase activity and increases NO production in HUVECs. Piceatannol 3'-O-glucoside inhibits lipoxygenase activity upto 66% at the concentration of 100 µM and IC50 value is 69 µM[1].

In order to ascertain whether Piceatannol 3'-O-glucoside (PG) ameliorates vascular function in wild-type (WT) and atherogenic model mice [apolipoprotein E-null mice (ApoE-/-)] and to investigate the possible underlying mechanism. Preincubation of aortic vessels from WT mice fed a normal diet (ND) with Piceatannol 3'-O-glucoside attenuates vasoconstriction response to U46619 and phenylephrine (PE), while the vasorelaxant response to acetylcholine (Ach) is markedly enhanced in an endothelium-dependent manner. Piceatannol 3'-O-glucoside treatment attenuates the phenylephrine (PE)-dependent contractile response, and significantly improves the acetylcholine (Ach)-dependent vasorelaxation response in aortic rings from ApoE-/- mice fed a high-cholesterol diet (HCD). Piceatannol 3'-O-glucoside administration in the drinking water significantly reduces fatty streak formation in ApoE-/- mice fed an HCD[2].

[1]. Woo A, et al. Piceatannol-3'-O-beta-D-glucopyranoside as an active component of rhubarb activates endothelial nitric oxide synthase through inhibition of arginase activity. Exp Mol Med. 2010 Jul 31;42(7):524-32. [2]. Woo A, et al. Arginase inhibition by piceatannol-3'-O-β-D-glucopyranoside improves endothelial dysfunctionvia activation of endothelial nitric oxide synthase in ApoE-null mice fed a high-cholesterol diet. Int J Mol Med. 2013 Apr;31(4):803-10.