Isolation and Identification of the Chemical Constituents in Ethyl Acetate Extracts of Wild Aquilaria sinensis Leaves
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Abstract:
The aim of this study was to explore the material basis for the pharmacological activities of Aquilaria sinensis leaves, which are the main components of the ‘Aquilaria Tea’ health food product series. Dried leaf powder was percolated with an aqueous solution containing 70% acetone and extracted several times using petroleum ether and ethyl acetate. Subsequently, seven compounds were isolated from the ethyl acetate extracts of wild Aquilaria sinensis leaves by multiple techniques including silica gel column chromatography, gel filtration chromatography (Sephadex LH-20), and preparative high performance liquid chromatography (PHPLC). Data from mass spectrometry (MS) and nuclear magnetic resonance (NMR) spectroscopy revealed the presence of six compounds: ergosterol (1), quercetin-3-O-?-D- galactopyranoside (2), stigmasterol (3), 5,4-dihydroxy-7-methoxyflavanone (4), ?-sitosterol (5), and quercetin-3-O-?-D-glucopyranoside (6). Based on their structures, the compounds could be classified as three sterols and their derivatives, two flavonoid glycosides, and one flavanone. Among them, compounds 1-2 were first isolated from the family Thymelaeaceae, and compound 4 was the first flavanone isolated from the genus Aquilaria (family Thymelaeaceae). The 2D NMR data and chemical shift assignments of compound 5 were reported here for the first time.
