Triterpenoid saponins from a cytotoxic root extract of Sideroxylon foetidissimum subsp. gaumeri Alberto Sánchez-Medina a , Philip C. Stevenson b,c , Solomon Habtemariam d , Luis M. Peña-Rodríguez e , Olivia Corcoran a , Anthony I. Mallet f , Nigel C. Veitch b, * a Medicines Research Group, School of Health and Bioscience, University of East London, University House, Romford Road, London E15 4LZ, UK b Jodrell Laboratory, Royal Botanic Gardens, Kew, Surrey TW9 3AB, UK c Natural Resources Institute, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK d Pharmacognosy and Phytotherapy Research Laboratories, Medway School of Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK e Grupo de Química Orgánica, Unidad de Biotecnología, Centro de Investigación Científica de Yucatán, A.C., Calle 43 No. 130 Col. Chuburná de Hidalgo. CP 97200, Mérida, Yucatán, Mexico f Medway School of Science, University of Greenwich, Central Avenue, Chatham Maritime, Kent ME4 4TB, UK article info Article history: Received 23 October 2008 Received in revised form 16 February 2009 Available online 22 April 2009 Keywords: Sideroxylon foetidissimum subsp. gaumeri Sapotaceae Yucatan peninsula Endemic Triterpenoid saponins Cytotoxic activity Medicinal plants HPLC NMR abstract Evaluation of the cytotoxicity of an ethanolic root extract of Sideroxylon foetidissimum subsp. gaumeri (Sapotaceae) revealed activity against the murine macrophage-like cell line RAW 264.7. Systematic bio- assay-guided fractionation of this extract gave an active saponin-containing fraction from which four saponins were isolated. Use of 1D ( 1 H, 13 C, DEPT135) and 2D (COSY, TOCSY, HSQC, and HMBC) NMR, mass spectrometry and sugar analysis gave their structures as 3-O-(b-D-glucopyranosyl-(1 ? 6)-b-D-glucopyr- anosyl)-28-O-(a-L-rhamnopyranosyl-(1 ? 3)[b-D-xylopyranosyl-(1 ? 4)]-b-D-xylopyranosyl-(1 ? 4)-a- L-rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-16a-hydroxyprotobassic acid, 3-O-b-D-glucopyran- osyl-28-O-(a-L-rhamnopyranosyl-(1 ? 3)[b-D-xylopyranosyl-(1 ? 4)]-b-D-xylopyranosyl-(1 ? 4)-a-L- rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-16a-hydroxyprotobassic acid, 3-O-(b-D-glucopyrano- syl-(1 ? 6)-b-D-glucopyranosyl)-28-O-(a-L-rhamnopyranosyl-(1 ? 3)-b-D-xylopyranosyl-(1 ? 4)[b-D-apio- furanosyl-(1 ? 3)]-a-L-rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-16a-hydroxyprotobassic acid, and the known compound, 3-O-b-D-glucopyranosyl-28-O-(a-L-rhamnopyranosyl-(1 ? 3)[b-D-xylopyranosyl- (1 ? 4)]-b-D-xylopyranosyl-(1 ? 4)-a-L-rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-protobassic acid. Two further saponins were obtained from the same fraction, but as a 5:4 mixture comprising 3- O-(b-D-glu- copyranosyl)-28-O-(a-L-rhamnopyranosyl-(1 ? 3)-b-D-xylopyranosyl-(1 ? 4)[b-D-apiofuranosyl-(1 ? 3)]- a-L-rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-16a-hydroxyprotobassic acid and 3-O-(b-D-apio- furanosyl-(1 ? 3)-b-D-glucopyranosyl)-28-O-(a-L-rhamnopyranosyl-(1 ? 3)[b-D-xylopyranosyl-(1 ? 4)]- b-D-xylopyranosyl-(1 ? 4)-a-L-rhamnopyranosyl-(1 ? 2)-a-L-arabinopyranosyl)-16a-hydroxyprotobassic acid, respectively. This showed greater cytotoxicity (IC 50 = 11.9 ± 1.5 lg/ml) towards RAW 264.7 cells than the original extract (IC 50 = 39.5 ± 4.1 lg/ml), and the saponin-containing fraction derived from it (IC 50 = 33.7 ± 6.2 lg/ml). Ó 2009 Elsevier Ltd. All rights reserved. 1. Introduction The Yucatan peninsula is considered a distinct biome, and as such includes the Mexican states of Campeche, Quintana Roo, and Yucatan, as well as parts of Chiapas and Tabasco, the north of Belize, and the Peten region of Guatemala (Durán et al., 2000). Included in its flora are 182 plant families comprising 992 genera and approximately 3000 species, 7.3% of which are endemic (Durán et al., 2000; Espadas-Manrique et al., 2003). Knowledge about the use of plants for therapeutic purposes has been preserved by some indigenous groups, and it is reported that more than 800 species, including 50 endemics, are used in Yucatecan traditional medicine (Durán et al., 1998). These include Sideroxylon foetidissimum Jacq. subsp. gaumeri Pittier (T.D.Penn), an endemic tree of the Sapota- ceae which is used mainly for timber and firewood. The fruits of this species are edible, and local people are said to use the plant for medicinal purposes, although no details on its preparation or application are available (Durán et al., 2000). Phytochemical and pharmacological studies of Sideroxylon are limited, and only a few species have been investigated. MeOH ex- tracts of the root of Sideroxylon cubense, a Caribbean species used externally to treat fractures, yielded the triterpenoid saponins sideroxyloside A and 3-O-b-D-glucopyranosyl-protobassic acid (Jiang et al., 1994). In addition, two further triterpenoid saponins, sideroxyloside B and sideroxyloside C, were reported from S. 0031-9422/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.phytochem.2009.03.014 * Corresponding author. Tel.: +44 208 332 5312; fax: +44 208 332 5310. E-mail address: n.veitch@kew.org (N.C. Veitch). Phytochemistry 70 (2009) 765–772 Contents lists available at ScienceDirect Phytochemistry journal homepage: www.elsevier.com/locate/phytochem