Anti‐obesity action of Salix matsudana leaves (Part 2). Isolation of anti‐obesity effectors from polyphenol fractions of Salix matsudana

Previously, it was reported that polyphenol fractions prepared from the leaves of Salix matsudana reduced the elevation of the rat plasma triacylglycerol level at 3 and 4 h after oral administration of a lipid emulsion containing corn oil, at a dose of 570 mg/kg. Moreover, body weights at 2–9 weeks and the nal parametrial adipose tissue weights were signicantly lower in mice fed the high‐fat diet with 5% polyphenol fractions of S. matsudana leaves than in those fed the high‐fat diet alone. The polyphenol fractions of S. matsudana leaves also signicantly reduced the hepatic total cholesterol content, which was elevated in mice fed the high‐fat diet alone. In addition, the polyphenol fractions of S. matsudana leaves inhibited palmitic acid uptake into brush border membrane vesicles prepared from rat jejunum and α ‐amylase activity, and their fractions enhanced norepinephrine‐induced lipolysis in fat cells. To clarify the active substances inhibiting the palmitic acid uptake into small intestinal brush border membrane, the α ‐amylase activity or enhancing the norepinephrine‐induced lipolyis in fat cells, the isolation of the active substances from polyphenol fraction was attempted using the above three assay systems. Compounds 1, 2 and 3 were isolated from the polyphenol fractions and identied as apigenin‐7‐ O ‐ d ‐glucoside, luteolin‐7‐ O ‐ d ‐glucoside and chrysoeriol‐7‐ O ‐ d ‐glucoside, respectively. Among three avonoids, apigenin‐7‐ O ‐ d ‐glucoside inhibited α ‐amylase activity, and luteolin‐7‐ O ‐ d ‐glucoside and chrysoeriol‐7‐ O ‐ d ‐glucoside inhibited palmitic acid uptake into small intestinal brush border membrane. Furthermore, three avonoid glucosides enhanced norepinephrine‐induced lipolysis in fat cells. Copyright © 2003 John Wiley & Sons, Ltd.