A New Flavone C -Glucoside from Aquilaria agallocha
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A NEW FLAVONE C-GLUCOSIDE FROM Aquilaria agallocha
C. T. Chang,1 C. L. Kao,2 H. C. Yeh,3 P. L. Song,3 H. T. Li,3 and C. Y. Chen4*
5,7,2′,3′,4′,5′-Hexahydroxyflavone 6-C-glucoside (1), 5-hydroxy-4′,7-dimethoxyflavone, luteolin-7,3′,4′trimethyl ether, 5,3′-dihydroxy-7,4′-dimethoxyflavone, persicogenin, quercetin-3-O-rhamnoside, kaempferol3-O-rhamnoside, isorhamnetin-3-O-rhamnoside, tamarixetin-3-O-rhamnoside, (+)-syringaresinol, (+)-diasyringaresinol, (+)-epi-syringaresinol, liriodendrin, methyl-β-D-xylopyranoside, methyl-β-Dglucopyranoside, and methyl-β-D-galactopyranoside were isolated from the seeds of Aquilaria agallocha (Thymelaeaceae). Among them, 1 is a new hexahydroxyflavone 6-C-glucoside. The structures of these compounds were characterized and identified by spectral analyses. Keywords: Aquilaria agallocha, Thymelaeaceae, hexahydroxyflavone, C-glucoside. The genus Aquilaria (Thymelaeaceae) is widely distributed in Asia. Aquilaria agallocha is of particular interest economically because it is the principal source of agarwood, one of the most highly valuable forest products currently traded internationally. The flowers of A. agallocha, which is widely cultivated in Guangdong, Hainan, and Taiwan Provinces in China, are orally reported to be used locally in trauma-related diseases such as fracture, bruise, etc. [1]. Previous phytochemical investigations on Chinese eaglewood revealed characteristic sesquiterpenes and chromone derivatives [2–15], but there have been no reports on the chemical constituents of the seeds [16, 17]. Previously, we have isolated flavonoids, benzenoids, and steroids from this plant [18–20]. To further understand the chemotaxonomy and to continue searching for novel agents from Thymelaeaceous plants, the seeds of A. agallocha were chosen for phytochemical investigation. These observations provide useful information for potential chemopreventive drug design. The chemical constituents in the seeds of A. agallocha were separated by column chromatography. A new flavone 1 and 15 known compounds, including eight flavonoids, 5-hydroxy4′,7-dimethoxyflavonoid (2) [20], luteolin-7,3′,4′-trimethyl ether (3) [21], 5,3′-dihydroxy-7,4′-dimethoxyflavone (4) [22], persicogenin (5) [23], quercetin-3-O-rhamnoside (6) [24], kaempferol-3-O-rhamnoside (7) [25], isorhamnetin-3-O-rhamnoside (8) [26], and tamarixetin-3-O-rhamnoside (9) [26], four lignans, (+)-syringaresinol (10) [27], (+)-dia-syringaresinol (11) [28], (+)-epi-syringaresinol (12) [28], and liriodendrin ((+)-syringaresinol-di-O-β-D-glucopyranoside) (13) [29], and three carbohydrates, methyl-β-D-xylopyranoside (14) [30], methyl-β-D-glucopyranoside (15) [31], and methyl-β-D-galactopyranoside (16) [32] were isolated from the seeds of A. agallocha. 5,7,2′,3′,4′,5′-Hexahydroxyflavone 6-C-glucoside (1) was obtained as a white amorphous powder from CH3OH. Its molecular formula was deduced as C21H20O13 by HR-ESI-MS m/z 503.0804 [M + Na]+ (calcd 503.0802). The UV spectrum of 1 contained absorption bands typical of the flavonoids [33]. The IR spectrum of
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