Pergamon PII: S0031-9422(96)00849-7 Phytochemistry, Vol. 45, No. 2, pp. 411415, 1997 © 1997 Elsevier Science Ltd All rights reserved. Printed in Great Britain 0031 9422/97 $17.00+0.00 WAHLENBERGIOSIDE, A PHENYLPROPANOID GLUCOSIDE FROM WAHLENBERGIA MARGINA TA WEI GUANGMA, REN XIANGTAN,* NICOLAFUZZATI,QINGSHENG LI,t JEAN-Luc WOLFENDER and KURT HOSTETTMANN~ Institut de Pharmacognosie et Phytochimie, Universit6 de Lausanne, BEP, CH-1015 Lausanne, Switzerland; * Institute of Biotechnology, Department of Biological Sciencesand Technology, Nanjing University, Nanjing 210093, P.R. China; t Yunnan College of Traditional Chinese Medicine, Kunming, Yunnan, 650011, P.R. China (Receivedin revised form 30 October 1996) Key Word Index--Wahlenberyia maryinata; Campanulaceae; wahlenbergioside; phenyl- propanoid glucoside. Abstraet--Wahlenbergioside, a new hydroxymethylglutaroyl phenylpropanoid glucoside, and a known compound, lobetyolin, were isolated from the methanol extract of Wahlenbergia marginata. The structures were determined by spectroscopic analysis and chemical degradations. © 1997 Elsevier Science Ltd. All rights reserved INTRODUCTION The whole herb of Wahlenbergia marginata (Thunb.) A. DC., a widely-used Chinese medicinal plant, has been employed for many years by different ethnic groups in the Yunnan Province for the treatment of coughs, pneumonia, tuberculosis and heart disease. It is also used as a tonic and haematopoietic [1]. However, due to the complexity of its constituents, little work has been done on the chemistry of the genus Wahlenbergia. As part of our phytochemical investigations on Chinese medicinal plants [2-8], W. rnarginata has been studied. RESULTSANDDISCUSSION Compound 1, named wahlenbergioside, was obtained as a colourless gum. In its negative ion FAB mass spectrum a deprotonated molecular ion was observed as the base peak at m/z = 515 [M-H]-, tog- ether with an intense dimer ion at m/z = 1031 [2 × M- H] . The molecular formula C23H32013 was deduced from the combined FAB-MS data, and JH and ~3C NMR data (Tables 1 and 2). The UV spectrum of 1 showed absorptions at 2max (MeOH) 220 and 265 nm and suggested that there was an aromatic system conjugated with an unsaturated side chain. In the 1H NMR spectrum ofl, the presence of a trans-propenyl alcohol moiety linked to a 3,4,5- trisubstituted phenyl residue was indicated by a pair :~ Author to whom correspondence should be addressed. of olefinic signals at 5 6.56 (1H, br d, J = 16.2 Hz, H- ?) and 6.23 (1H, dt, J = 16.2, 7.6 Hz, H-fl), and a broadened methylene doublet (J = 7.6 Hz) at 3 4.72 (H<t) as well as two meta-coupled aromatic doublets (J = 2 Hz) at 5 6.62 and 6.59. A three-proton singlet at 6 3.84 was characteristic of a methoxyl group situ- ated on an aromatic nucleus. Furthermore, a methyl singlet at 5 1.38 (6'-Me), a methyl ester singlet at 8 3.66 (-OMe), and a pair of methylene singlets at 5 2.71 (H-2' and H-4'), together with two carbonyl signals at ~ 173.3 (C-I') and 176.7 (C-5') demonstrated the presence of a methyl ester derivative of a 3-oxygenated 3-methylglutarate moiety (HMG) [9]. This diester chain was shown to be at C-~t by the downfield shifted methyleneoxy doublet of H-a at 6 4.72 when compared with the shifts of analogues reported previously [9, 10]. The ~H and ~3C NMR spectra also showed a set of signals of a saccharide unit. This information suggested that 1 was a 'tangshenoside type' phe- nylpropanoid derivative [9, 10]. Comparison of the spectral data of I with those of tangshenoside I (T-I) (see Fig. 1) revealed that there was only one saccharide unit and one methoxyl group in compound 1 instead of two glucoses and two methoxyl groups as in the case of T-I. Acid hydrolysis of 1 with 2 M HC1, followed by a comparison with authentic sugar samples on HPTLC plates [11], indicated that glucose was the saccharide unit of 1. However, the glucose unit could either be located on the HMG chain or on the aromatic nucleus. In order to prove the attachment position of the glu- cose unit, alkaline hydrolysis of 1 with 0.5 M KOH, followed by acetylation was carried out. This reaction 411