Journal of Chromatography A, 1089 (2005) 59–64 Liquid chromatography–diode array detection–electrospray ionisation mass spectrometry/nuclear magnetic resonance analyses of the anti-hyperglycemic flavonoid extract of Genista tenera Structure elucidation of a flavonoid-C-glycoside Am´ elia P. Rauter a,∗ , Alice Martins a , Carlos Borges a , Joana Ferreira a , Jorge Justino b , Maria-Ros´ ario Bronze c , Ana V. Coelho c , Young H. Choi d , Robert Verpoorte d a Departamento de Qu´ ımica e Bioqu´ ımica/Centro de Qu´ ımica e Bioqu´ ımica, Faculdade de Ciˆ encias da Universidade de Lisboa, Ed. C8, 5 ◦ Piso, 1749-016 Lisboa, Portugal b Escola Superior Agr ´ aria de Santar´ em, Instituto Polit´ ecnico de Santar´ em, Apartado 279, 2001-904 Santar´ em, Portugal c Instituto de Tecnologia Qu´ ımica e Biol ´ ogica, Universidade Nova de Lisboa, Apartado 127, 2891-901 Oeiras, Portugal d Division of Pharmacognosy, Section Metabolomics, Institute of Biology, Leiden University, P.O. Box 9502, 2300 RA Leiden, The Netherlands Received 21 February 2005; received in revised form 3 June 2005; accepted 8 June 2005 Abstract The anti-hyperglycemic flavonoid extract obtained from Genista tenera was first studied by liquid chromatography (LC)–diode array detection (DAD) which showed the presence of two major compounds. One of them was identified as genistein-7-O-glucoside. Luteolin-7-O- glucoside was detected as a minor constituent, while luteolin-7,3 ′ -di-O-glucoside and rutin were found in trace amounts. LC–DAD–ESI–MS and NMR were used to confirm the structure of these compounds and allowed the elucidation of the structure of the unknown major compound, which is the flavonoid 5,7,4 ′ -trihydroxyisoflavone-8-C-glucoside. © 2005 Elsevier B.V. All rights reserved. Keywords: Genista tenera; LC–DAD–ESI–MS; NMR; Flavonoid glycoside; 5,7,4 ′ -Trihydroxyisoflavone-8-C-glucoside 1. Introduction Genista tenera (Jacq. Ex Murr) O. Kuntze is an endemic plant to the Island of Madeira and belongs to the Legumi- nosae family. The infusion of its aerial parts is used by the local population as an adjuvant for the treatment of diabetes. Previous studies of the secondary metabolites of Genista species reported alkaloids and flavonoids as the chemotax- onomic markers of the genus Genista [1]. The alkaloids extracted from the aerial parts of the plant studied in this work have recently been described [2]. A previous investigation of the diethyl ether extract of G. tenera afforded the flavones ∗ Corresponding author. Tel.: +351 21 7500952; fax: +351 21 7500088. E-mail address: aprauter@fc.ul.pt (A.P. Rauter). apigenin and chrysoeriol, and the isoflavones genistein, 3 ′ -O- methylorobol, 5-O-methylgenistein and alpinumisoflavone, which were characterized by FAB-MS/MS [3,4]. There is growing evidence that supports a protective role of flavonoids in cardiovascular diseases and various types of cancer [5,6]. Apigenin is a dietary bioflavone with anticarcinogenic prop- erties, which is thought to play a role in cancer chemopre- vention and cancer chemotherapy [7,8]. Also the flavone lute- olin has been reported as an anticancer agent [9–11]. Some isoflavones, e.g. genistein, possess anticancer activity [12] and estrogen-like activities, which could have a beneficial role in humans against estrogen deficiency [13,14]. Further- more, flavonoids have been recently reported as aldose reduc- tase inhibitors blocking the sorbitol pathway that is linked to many problems associated with diabetes [15]. A preliminary 0021-9673/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.chroma.2005.06.046