Pentacyclic triterpenes from Euphorbia stygiana Elisabete M.C. Lima a, *, Jorge M.R. Medeiros a , Laurence B. Davin b a Department of Technological Sciences, University of Azores, 9501-801 Ponta Delgada, Ac ¸ ores, Portugal b Institute of Biological Chemistry, Washington State University, PO Box 646340, Pullman, WA 99164-6340, USA Received 6 August 2002; received in revised form 20 December 2002 Abstract Two pentacyclic triterpenes, D-friedomadeir-14-en-3b-yl acetate and D:C-friedomadeir-7-en-3b-yl acetate, named madeiranyl acetate and isomadeiranyl acetate, respectively, were isolated from leaves of Euphorbia stygiana, together with the two known madeiranes, D-friedomadeir-14-en-3-one and D:C-friedomadeir-7-en-3-one, which were obtained from the stem bark. In addition, four known lupane and taraxerane-type triterpenes, namely lupenyl acetate, lupenone, taraxeryl acetate and taraxerone, were also iso- lated from the same source. Structures were elucidated by physical, chemical and spectroscopic methods ( 1 H NMR, 13 C NMR, IR and mass spectra) and by comparison with literature data, and in the case of D:C-friedomadeir-7-en-3b-yl acetate by X-ray analysis as well. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Euphorbia stygiana; Euphorbiaceae; Pentacyclic triterpenes; Madeiranes; Lupanes; Taraxeranes 1. Introduction Euphorbia stygiana Watson (Euphorbiaceae), a shrub endemic to the archipelago of Azores, is closely related to Euphorbia mellifera Ait., with the latter being found in the archipelago of Madeira and in two of the Canary islands. E. stygiana produces a latex which causes irri- tation of the skin and eyes during collection, and has also been reported to possess molluscicidal activity (Mendonc¸a et al., 1993). However, no chemical investi- gation on this plant has been reported up to now. In this regard, the plant was screened for triterpenoids and four pentacyclic triterpenes were found with a madeirane skeleton: of these, two were new triterpenes, D-friedo- madeir-14-en-3b-yl acetate and D:C-friedomadeir-7-en- 3b-yl acetate, named madeiranyl acetate (1a) and iso- madeiranyl acetate (2a), respectively, and the others were the two known triterpenes, D-friedomadeir-14-en- 3-one (1b) and D:C-friedomadeir-7-en-3-one (2b), pre- viously isolated from E. mellifera (Ferreira, 1990). In addition, four known pentacyclic triterpenes of the lupane and taraxerane-type skeleton were also isolated: lupenyl acetate, taraxeryl acetate, lupenone and tarax- erone. The acetates were isolated from the leaves and the ketones from the stem bark. 2. Results and discussion The acetone extracts from the air-dried stem bark and leaves of E. stygiana were individually partitioned between 85% aqueous MeOH and n-hexane. Each of the corresponding n-hexane soluble fractions were then saponified, with the non-saponifiable constituents being subjected to silica gel column chromatography using n- hexane–EtOAc gradients as eluants. Recrystallization of the resulting fractions yielded eight pentacyclic tri- terpenes: four acetates, madeiranyl acetate (1a), iso- madeiranyl acetate (2a), lupenyl acetate and taraxeryl acetate, isolated from the leaves, and four ketones, madeiranone (1b), isomadeiranone (2b), lupenone and taraxerone, isolated from the stem bark. The acetates 1a and 2a are new compounds, whereas ketones 1b and 2b were previously reported in E. mellifera. The struc- tures of the lupane and taraxerane-type triterpenes were established according to spectral data analysis and by comparison with published reported data (Lima, 2000). The molecular formulae, C 32 H 52 O 2 , of the acetates 1a and 2a, and C 30 H 48 O, of the ketones 1b and 2b, 0031-9422/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. PII: S0031-9422(03)00007-4 Phytochemistry 63 (2003) 421–425 www.elsevier.com/locate/phytochem * Corresponding author. Tel.: +351-296-650171; fax: +351-296- 650172. E-mail address: elis@notes.uac.pt (E.M.C. Lima).