Four New Prenylated Flavonoids from the Fruits of Sinopodophyllum hexandrum
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FOUR NEW PRENYLATED FLAVONOIDS FROM THE FRUITS OF Sinopodophyllum hexandrum
Yan-jun Sun,1,2,3* Rui-jie Han,1,2 Chen Zhao,1,2 Hui Chen,1,2 Yan-li Zhang,1,2 and Wei-sheng Feng1,2*
Four new prenylated flavonoids, sinoflavonoids NF–NI (1–4), were isolated from the fruits of Sinopodophyllum hexandrum by different chromatographic methods such as silica gel, Sephadex LH-20, ODS, and preparative high-performance liquid chromatography (HPLC). Their structures were elucidated on the basis of extensive spectroscopic data (UV, IR, HR-ESI-MS, 1H NMR, 13C NMR, HSQC, HMBC). Keywords: Sinopodophyllum hexandrum, prenylated flavonoids, structure identification. With their chemical and pharmacological diversity, prenylated flavonoids have attracted much attention from natural product chemists [1]. Sinopodophyllum hexandrum, widely distributed in the Southwest of China, is a member of the Berberidaceae family [2]. Its roots and rhizomes are mainly used for extracting podophyllotoxin [3]. However, its fruits are clinically applied for the treatment of amenorrhea, dead fetus, and placental retention [4]. Previous phytochemical investigations revealed that S. hexandrum is particularly rich in aryltetralin lactone lignans and prenylated flavonoids [2, 4–12]. As part of our continuous efforts toward discovering new natural products, four new prenylated flavonoids, sinoflavonoids NF–NI (1–4), were isolated from the fruits of S. hexandrum. Details of the isolation and structure elucidation of all isolated compounds are described here (Fig. 1). The EtOH extract of the fruits of S. hexandrum was partitioned between petroleum ether (PE), CH2Cl2, EtOAc, n-BuOH, and water. The EtOAc layer was fractionated and purified by repeated column chromatography, allowing the isolation of four new prenylated flavonoids, sinoflavonoids NF–NI (1–4). Their structures were elucidated on the basis of extensive spectroscopic data (UV, IR, HR-ESI-MS, 1H NMR, 13C NMR, HSQC, HMBC). Compound 1 was obtained as a yellow amorphous powder and possesses the molecular formula C21H20O7, as revealed from its HR-ESI-MS analysis (m/z 383.1129 [M – H]–, calcd 383.1131). The 1H NMR (Table 1) spectrum showed two aromatic systems including one 1,3,4-tri-substituted benzene ring at δ 7.53 (1H, d, J = 2.2 Hz), 6.89 (1H, d, J = 8.5 Hz), and 7.42 (1H, dd, J = 8.5, 2.2 Hz), one penta-substituted benzene ring at δ 6.42 (1H, s), one 2,2-dimethyldihydropyrano group [based on the HMBC correlations of methyl groups at δ 1.31 (6H, s, H-4′′, 5′′) with C-3′′ (δ 76.2), and C-2′′ (δ 30.9) and a methylene group at δ 1.81 (2H, t, J = 6.8 Hz, H-2′′) with C-3′′ (δ 76.2) and C-1′′ (δ 15.7)], one aromatic methoxy group at δ 3.76 (3H, s), and three phenolic hydroxyl groups at δ 13.05 (1H, s), 9.76 (1H, s), and 9.37 (1H, s). The 13C NMR (Table 2) spectrum revealed a flavonol skeleton, including one carbonyl group at δ 178.0, two benzene rings, two oxygen-bearing olefinic carbons at δ 155.3, 137.5, one 2,2-dimethyldihydropyrano group at δ 15.7, 30.9, 76.2, 26.3 (× 2), and one aromatic methoxy group at
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