In the course of our phytochemical studies of North American useful plants, we investigated the chemical constituents in Juniperus plants. Genus Juniperus belongs to family Cupressaceae and it comprises about 70 species distributed in the Northern Hemisphere. Juniperus communis is a familiar species with the characteristic flavor of distilled liquor gin. In this report we present the structural determination and biological activities of phenolic components of J. communis var. depressa and J. occidentalis collected in Oregon, U.S.A. From the methanolic extracts of the two Juniperus plants, 22 flavonoids (1-22), 15 neolignan (lignan) glycosides (23-37) and 17 phenylpropanoids (phenylethanoids) (38-54) were isolated and thier structures were established on the basis of spectral and chemical evidence. Among them, biflavonoids (1, 2), flavan glucosides (6, 7), neolignan glycosides (23, 24, 30-32, 35), phenylethanoids (38, 39) and phenylpropanoids (41, 48) were new compounds. Compounds 1 and 2, obtained from J. communis var. depressa, were confirmed to be atropisomers of cupressuflavone 4'-O-β-D-glucopyraonoside. The absolute stereochemistries of 1 and 2 were determined to be aR and aS, respectively, by CD spectra. Although cupressuflavone has been isolated from various gymnosperms, 1 and 2 are the first instance of its glycosides. The inhibitory activities of some isolated compounds on the Maillard reaction and lipid peroxide formation were examined. As a result, (-)-catechin (10) and (+)-epicatechin (11) strongly inhibited AGEs formation in the Maillard reaction. Similarly, some flavonoids showed moderate inhibitory activities on the Maillard reaction and lipid peroxide formation.
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