Studies on physiologically active substances in citrus peel. Part II. Structure and hypotensive effect of flavonoid glycosides in Citrus unshiu peelings.

Abstract

An attempt was made to isolate hypotensive substances from a hot water extract of Citrus unshiu. Six flavonoid glycosides were isolated by repeated chromatography and gel nitration after extraction with butanol and treatment with lead subacetate. Their structures were established to be limocitrin 3-β-D-glucose (1), limocitrin-3-α-L-rhamnose (2), 3, 6-di-C-glucosylapigenin (3), narirutin (4), rutin (5) and narcissin (6) by UV, 1H-NMR and 13C-NMR spectroscopy and sugar analysis. Each component was intravenously injected into SHR-SP rats (1 mg/100 g body weight), and 3 and 5 were found to lower their blood pressure. Among these compounds, 2 and 3 were a new flavonol and flavone glycoside, respectively.