Chemical Constituents of the Roots of Triosteum pinnatifidum

Abstract

The genus Triosteum Linn., belonging to the family Caprifoliaceae, consists of about eight species mainly distributed in East Asia and North America [1]. In traditional Chinese medicine the roots of T. pinnatifidum Maxim., locally known as “Tian Wang Qi,” are used for the treatment of rheumatic lumbocrural pain, bruises, dyspepsia, and menoxenia [2]. Ten iridoids have been reported from the title plant, which were the characteristic constituents of the Triosteum genus [3]. In continuation of our studies on chemical constituents from the roots of T. kirilowii, 17 compounds were isolated and elucidated as loganic acid (1), epi-vogeloside (2), 7-O-butylsecologanic acid (3), foliasacioside B1 (4), 3,5-di-O-caffeoyl quinic acid (5), methyl 3,5-di-O-caffeoyl quinate (6), 4,5-di-O-caffeoyl quinic acid (7), methyl 4,5-di-O-caffeoyl quinate (8), 4,5-di-O-caffeoyl quinic acid butyl ester (9), chlorogenic acid butyl ester (10), caffeic acid (11), ethyl caffeate (12), ursolic acid (13), betulin (14), -sitosterol (15), daucosterol (16), and daucosterol-6 -O-palmitate (17). To the best of our knowledge, all these compounds were obtained from the genus Triosteum for the first time. General. 1H and 13C NMR spectra were obtained on Varian INOVA 500 MHz (Varian, USA) or Bruker Avance DRX 400 MHz spectrometers (Bruker, Switzerland). All solvents used were of analytical grade (Tianjin Jiangtian Chemical Technology Co. Ltd., China). Silica gel (100–200 and 200–300 mesh, Qingdao Haiyang Chemical Co. Ltd., China), Sephadex LH-20 gel (Amersham Pharmacia Biotech AB, Sweden), LiChroprep RP-18 (40–63 m, Merck, Germany), and resin D101 (Tianjin Haiguang Chemical Co. Ltd., China) were used for column chromatography. TLC was carried out using precoated plates with GF254 silica gel (Qingdao Haiyang Chemical Co. Ltd., China). Spots on TLC were visually observed under UV light and by spraying with 5% H2SO4 reagent followed by heating. Plant Material. The roots of T. pinnatifidum were collected from Mei County, Shaanxi Province of China in August 2006, and authenticated by Prof. Zhen-Hai Wu, Northwest A F University. A voucher specimen (S200608007) was deposited in the herbarium of School of Pharmaceutical Science and Technology, Tianjin University, China. Extraction and Isolation. The air-dried powdered roots (20 kg) were refluxed with 95% EtOH and then with 60% EtOH twice. The extract was suspended in water and successively partitioned with petroleum ether (60–90 C), CHCl3, EtOAc, and n-BuOH in turn. The petroleum ether extract (80 g) was subjected to silica gel column chromatography eluting with petroleum ether–EtOAc (98:2 7:3) in a gradient manner to afford compounds 14 (20 mg) and 15 (2 g). The EtOAc extract (260 g) was subjected to silica gel column chromatography eluting with CH2Cl2–MeOH (97:3 8:2) in a gradient manner, and 88 fractions were collected. Fractions 16–18 were chromatographed over a silica gel column repeatedly and recrystallized with Me2CO to afford compound 13 (60 mg). Fractions 19–29 were subjected to silica gel column chromatography and further purified by Sephadex LH-20 to yield compound 12 (50 mg). Fractions 30–36 were purified by silica gel column chromatography and recrystallized to give compound 17 (80 mg). Fractions 49–55 were recrystallized with Me2CO to obtain compound 16 (560 mg). The n-BuOH extract (1.4 kg) was chromatographed over a D101 macroporous resin column eluting with H2O and 30%, 50%, 70%, and 95% EtOH. The 30% EtOH eluate (400 g) was subjecred to silica gel column chromatography eluting with EtOAc–MeOH (95:5 6:4) in a gradient manner. Fractions 1–2 were subjected to silica gel column chromatography and