a-Glucosidase inhibitory pentacyclic triterpenes from the stem bark of Fagara tessmannii (Rutaceae) Luc Meva’a Mbaze a , Herve Martial P. Poumale b,c , Jean Duplex Wansi a, * , Jean Alexandre Lado a , Shamsun Nahar Khan d , Muhammad Choudhary Iqbal d , Bonaventure Tchaleu Ngadjui c , Hartmut Laatsch b a Department of Chemistry, Faculty of Science, University of Douala, P.O. Box 24157, Douala, Cameroon b Department of Organic and Biomolecular Chemistry, University of Go ¨ ttingen, Tammannstrasse 2, D-37077 Go ¨ ttingen, Germany c Department of Organic Chemistry, Faculty of Science, University of Yaounde I, P.O. Box 812, Yaounde, Cameroon d H.E.J Research Institute of Chemistry, University of Karachi, Karachi 75270, Pakistan Received 8 September 2006; received in revised form 11 December 2006 Available online 31 January 2007 Abstract In addition to fatty acids, a mixture of sterols (b-sitosterol, stigmasterol, campesterol and stigmastanol), lupeol, arctigenin methyle- ther, sesamin, vanillic acid (1), 2,6-dimethoxy-1,4-benzoquinone (2), betulinic acid and two pentacyclic triterpene acetates were isolated from Fagara tessmannii Engl. They were identified as 3b-acetoxy-16b-hydroxybetulinic acid (3a) and 3b,16b-diacetoxybetulinic acid (3b), and their structures were established using 1 and 2D NMR spectra and by comparison with published data. Two derivatives of the com- pounds were prepared. Some isolated compounds were evaluated for their antifungal and antibacterial activities. Compounds 1 and 3a showed significant inhibition of a-glucosidase. Ó 2007 Elsevier Ltd. All rights reserved. Keywords: Fagara tessmannii; Rutaceae; Pentacyclic triterpene; Antifungal; Antibacterial; a-Glucosidase inhibition 1. Introduction Fagara tessmannii Engl. (Rutaceae) (Syn. Zanthoxylum tessmannii) is a shrub of the African rainforests in South-West, Centre, South and East provinces in Camer- oon. In the traditional medicine, it is used locally for the treatment of tumors, swellings, inflammation and gonor- rhoea (Raponda-Walker and Sillans, 1961). The root bark of this plant is used in West Africa in traditional medicine as a toothbrush (Kerharo and Adam, 1971). Previous phy- tochemical studies of F. tessmannii collected at three differ- ent localities in Cameroon resulted in the isolation of alkaloids, lignans, triterpenes and steroids (Ayafor et al., 1984). The widespread use of F. tessmannii in indigenous medicine for different ailments, as well as the antifungal and antioxidant activities exhibited by the genus (Chaaib et al., 2003), justified further attempts to isolate and iden- tify active compounds. In this paper, we report the isola- tion and structure elucidation of two new pentacyclic triterpene acetates, and their biological activities. 2. Results and discussion The stem bark of F. tessmannii was extracted with MeOH. The extract was submitted to repeated column chromatography and preparative TLC (PTLC) to afforded fatty acids, a mixture of sterols (b-sitosterol, stigmasterol, campesterol and stigmastanol), lupeol, arctigenin methyle- ther, sesamin, betulinic acid, vanillic acid (1), 2,6-dime- thoxy-1,4-benzoquinone (2), and two new pentacyclic triterpene acetates (3a, 3b). The 1 H and 13 C NMR, and 0031-9422/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2006.12.015 * Corresponding author. Tel.: +237 781 77 31. E-mail address: jdwansi@yahoo.fr (J.D. Wansi). www.elsevier.com/locate/phytochem Phytochemistry 68 (2007) 591–595 PHYTOCHEMISTRY