Inhibition of hepatic neoglucogenesis and glucose‐6‐phosphatase by quercetin 3‐O‐α(2″‐galloyl)rhamnoside isolated from Bauhinia megalandra leaves

Abstract

AbstractIn intact microsomes, quercetin 3‐O‐α‐(2″‐galloyl)rhamnoside (QGR) inhibits glucose‐6‐phosphatase (G‐6‐Pase) in a concentration‐dependent manner. QGR increased the G‐6‐Pase Km for glucose‐6‐phosphate without change in the Vmax. The flavonol did not change the kinetic parameters of disrupted microsomal G‐6‐Pase or intact or disrupted microsomal G‐6‐Pase pyrophosphatase (PPase) activity. This result allowed the conclusion that QGR competitively inhibits the glucose‐6‐phosphate (G‐6‐P) transporter (T1) without affecting the catalytic subunit or the phosphate/pyrophosphate transporter (T2) of the G‐6‐Pase system.QGR strongly inhibits the neoglucogenic capacity of rat liver slices incubated in a Krebs‐Ringer bicarbonate buffer, supplemented with lactate and oleate saturated albumin.The QGR G‐6‐Pase inhibition might explain the decrease in the liver slice neoglucogenic capacity and, in turn, could reduce glucose levels in diabetic patients. Copyright © 2005 John Wiley & Sons, Ltd.