Phenylpropanoids from subterranean organs of Inula helenium

Abstract

Inula helenium L. is a plant species of the family Asteraceae. Its rhizomes and roots are widely used in medical practice. Glucofructans [1], sesquiterpenes [2], thymol derivatives [3], and dammaradienyl acetate [4] were observed earlier in roots of I. helenium. No information is available on phenolic compounds from roots of I. helenium. Preliminary studies showed that subterranean organs of I. helenium contained phenylpropanoids, the chemical study of which is the focus of the present work. Subterranean organs of I. helenium were collected at the experimental plantation in the vicinity of Goryachinsk (Pribaikal Region, Republic of Buryatiya, 30 Aug., 2009, 52°48 98 N, 108°29 01 E). The species was determined by Dr. T. A. Aseeva (IGEB, SB, RAS). Extraction and Fractionation. Ground raw material (1.5 kg) was extracted (5 ) with EtOH (60%, 1:10, 2 h) on a boiling-water bath. The combined EtOH extracts were concentrated to a watery residue that was extracted with C6H14, CHCl3, EtOAc, and BuOH to produce C6H14 (61.8 g, 4.12% of air-dried raw material mass), CHCl3 (24.2 g, 1.61%), EtOAc (7.8 g, 0.52%), and BuOH fractions (260.9 g, 17.39%) and an aqueous residue (166.2 g, 11.08%). The EtOAc fraction (5 g) was chromatographed over Sephadex LH-20 (3 120 cm) using an EtOH:H2O gradient (96:4 0:100) with subsequent column chromatography (CC) of subfractions over polyamide (5 10, H2O:EtOH eluent, 0:100 96:4) and preparative TLC on cellulose (solvent systems 1 and 2) and SiO2 (solvent system 3). The separation isolated from the EtOAc fraction nine compounds that were identified by MS, UV, IR and 13C NMR spectroscopy as the methyl ester of caffeic acid (1, 12 mg) [5]; caffeic (2, 31 mg) [6]; 3,5-di-O-caffeoylquinic (3, 17 mg); 1,5-di-O-caffeoylquinic (4, 16 mg) [7]; 2,3-di-O-caffeoyltartaric (chicoric, 5, 11 mg) [8]; 2-O-caffeoyltartaric (caftaric, 6, 37 mg) [9]; 5-O-caffeoylquinic (7, 12 mg) [6]; and 3-O-caffeoylquinic acids (8, 46 mg) [10]; and echinacoside (9, 11 mg) [11]. Echinacoside (9), C35H46O20. UV spectrum (MeOH, max, nm): 221, 246 sh, 290 sh, 330. FAB-MS (m/z): 785 [M – H]–. 13C NMR spectrum (125 MHz, DMSO-d6): dihydroxyphenylethanol: 146.27 (C-4), 144.31 (C-3), 134.22 (C-1), 121.24 (C-6), 117.10 (C-5), 116.21 (C-2), 72.00 (C-7), 36.21 (C-8); caffeate: 168.92 (C-9), 149.93 (C-4), 148.21 (C-8), 146.63 (C-3), 127.56 (C-1), 123.24 (C-6), 116.11 (C-2), 115.11 (C-7), 114.69 (C-5); glucose I: 104.15 (C-1), 81.50 (C-3), 74.61 (C-2), 73.60 (C-5), 70.43 (C-4), 69.52 (C-6); glucose II: 104.08 (C-1), 77.80 (C-3), 76.16 (C-5), 74.83 (C-2), 71.39 (C-4), 62.60 (C-6); rhamnose: 102.57 (C-1), 73.63 (C-4), 72.17 (C-2, C-3), 70.27 (C-5), 18.27 (C-6).