Angustilobine and andranginine type indole alkaloids and an uleine–secovallesamine bisindole alkaloid from Alstonia angustiloba Wai-Foong Ku a , Shin-Jowl Tan a , Yun-Yee Low a , Kanki Komiyama b , Toh-Seok Kam a,⇑ a Department of Chemistry, University of Malaya, 50603 Kuala Lumpur, Malaysia b The Center for Basic Research, Kitasato University, 5-9-1, Shirokane, Minato-ku, Tokyo 108-8642, Japan article info Article history: Received 23 March 2011 Received in revised form 5 July 2011 Available online 31 August 2011 Keywords: Apocynaceae Alstonia angustiloba Alkaloids Bisindole NMR Cytotoxicity abstract A total of 20 alkaloids were isolated from the leaf and stem-bark extracts of Alstonia angustiloba, of which two are hitherto unknown. One is an alkaloid of the angustilobine type (angustilobine C), while the other is a bisindole alkaloid angustiphylline, derived from the union of uleine and secovallesamine moieties. The structures of these alkaloids were established using NMR and MS analysis. Angustilobine C showed moderate cytotoxicity towards KB cells. Ó 2011 Elsevier Ltd. All rights reserved. 1. Introduction Plants of the genus Alstonia (Apocynaceae), which are usually shrubs or trees, are distributed over the tropical parts of Central America, Africa and Asia (Markgraf, 1974; Sidiyasa, 1998; Whitmore, 1972). Plants belonging to this genus represent a rich source of biologically-active indole and bisindole alkaloids (Arai et al., 2010; Atta-ur-Rahman et al., 1991, 1994; Cai et al., 2007, 2008, 2010; Carroll et al., 2005; Feng et al., 2009a,b; Ghedira et al., 1988; Hamaker and Cook, 1994; Hirasawa et al., 2009a,b; Kam, 1999; Kam and Choo, 2000, 2003, 2004a,b,c, 2006; Kam et al., 1999, 2004a, 2008; Keawpradub and Houghton, 1997; Keawpra- dub et al., 1997, 1999a,b; Koyama et al., 2008, 2010a,b; Macabeo et al., 2005; Salim et al., 2004; Tan et al., 2010a,b; Wang et al., 2009; Wright et al., 1992, 1993; Zhou et al., 2005), and several spe- cies have been reported to be used in the treatment of malaria and dysentery (Burkill, 1966; Perry and Metzger, 1980). About six species occur in the Peninsular Malaysia and are mainly found in both the lowland and highland forest, as well as in swampy areas (Sidiyasa, 1998; Whitmore, 1972). In continuation of studies of the alkaloids of this genus (Kam and Choo, 2000, 2003, 2004a,b,c; Kam et al., 1997, 1999, 2004a, 2008; Tan et al., 2010a,b), we wish to report the alkaloidal composition as well as the isolation of new biologically-active alkaloids from Alstonia angustiloba Miq. There have been several previous phytochemical investigations of this species (Kam and Choo, 2004b; Koyama et al., 2008; Ravao et al., 1985; Zeches et al., 1984, 1987). 2. Results and discussion The EtOH extract of the leaves of A. angustiloba provided a total of 13 alkaloids, including the new angustilobine type alkaloid, angustilobine C (1), and the andranginine derivative andransinine 0031-9422/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2011.08.001 ⇑ Corresponding author. Tel.: +60 3 79674266; fax: +60 3 79674193. E-mail address: tskam@um.edu.my (T.-S. Kam). Phytochemistry 72 (2011) 2212–2218 Contents lists available at SciVerse ScienceDirect Phytochemistry journal homepage: www.elsevier.com/locate/phytochem