Chemical Constituents of the Roots of Trichosanthes kirilowii

Abstract

The genus Trichosanthes Linn. (Cucurbitaceae) is composed of about 50 species distributed mainly in Southeast Asia. In traditional Chinese medicine the roots of Trichosanthes kirilowii Maxim., commonly known as “Tian Hua Fen,” are used for the treatment of cough, inflammation, polydipsia, and diabetes [1]. Most previous phytochemical studies of T. kirilowii have focused on the fruits and seeds, and triterpenoids, sterols, amino acid, lipids, and other compounds have been isolated from different parts of the plant [2–5]. In our research on chemical constituents of the roots of T. kirilowii, which has rarely been reported in recent years, 18 compounds were isolated and elucidated as 2,3,4,9-tetrahydro-1H-pyrido[3,4-b]indole-3-carboxylic acid (1), allantoin (2), nicotinic acid (3), xanthine (4), adenine (5), uracil (6), thymine (7), guanosine (8), uridine (9), phenylalanine (10), tyrosine (11), 1-C-(p-hydroxyphenyl)-glycerol (12), furoic acid (13), p-hydroxybenzoic acid (14), p-hydroxybenzaldehyde (15), succinic acid (16), -spinasterol-3-O-D-glucopyranoside-6 -O-palmitate (17), and bryonolic acid (18). Plant Material. The roots of Trichosanthes kirilowii were collected from Hebei Province of China in July 2010 and authenticated by Prof. Tian-Xiang Li, Tianjin University of Traditional Chinese Medicine. A voucher specimen was deposited in the herbarium of pharmacognosy, Tianjin University of Traditional Chinese Medicine. Extraction and Isolation. The air-dried roots (14 kg) were cut into small pieces and refluxed with 95% EtOH and then with 50% EtOH twice. The extract was suspended in water and successively partitioned with petroleum ether (60–90 C), CH2Cl2, EtOAc, and n-BuOH in turn. The petroleum ether extract (45 g) was subjected to silica gel column chromatography eluting with petroleum ether–EtOAc in a gradient manner, and further purified by silica gel and Sephadex LH-20 column chromatography repeatedly to afford compounds 17 (80 mg) and 18 (25 mg). The CH2Cl2 extract (30 g) was subjected to silica gel column chromatography eluting with gradient CH2Cl2–EtOAc to get compounds 12 (8 mg) and 15 (6 mg). The EtOAc extract (18 g) was repeatedly separated by silica gel, Sephadex LH-20, and preparative TLC to yield compounds 2 (85 mg), 3 (5 mg), 4 (5 mg), 6 (72 mg), 9 (3 mg), 13 (7 mg), 14 (15 mg), and 16 (100 mg). The n-BuOH extract (170 g) was chromatographed over a D101 macroporous resin column eluting with H2O and 30%, 50%, 70%, and 95% EtOH. The 30% eluate (37 g) was subjected to silica gel column chromatography and further purified on Sephadex LH-20 and ODS columns to give compounds 1 (20 mg), 5 (20 mg), 7 (3 mg), 8 (150 mg), 10 (80 mg), and 11 (8 mg). The structures of the compounds were identified by a combination of spectroscopic methods (MS, 1H NMR, and 13C NMR) and physicochemical properties. The spectroscopic data of all the compounds were in good agreement with the literature data. 1H and 13C NMR spectra were recorded on 400 MHz and 600 MHz Bruker AV III spectrometers (Bruker, Switzerland). ESI-MS data were obtained on a Waters Quattro Premier XE mass spectrometer (Waters, USA). Silica gel (100–200 and 200–300 mesh, Qingdao Haiyang Chemical Co. Ltd., China), Sephadex LH-20 gel (GE Healthcare Bio-Sciences AB, Sweden), ODS (YMC Co. Ltd, Japan), and D101 resin (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.