Toxicology Letters 216 (2013) 189–199 Contents lists available at SciVerse ScienceDirect Toxicology Letters jou rn al h om epage: www.elsevier.com/locate/toxlet The cucurbitacins E, D and I: Investigation of their cytotoxicity toward human chondrosarcoma SW 1353 cell line and their biotransformation in man liver Suzanne Abbas a,∗ , Jean-Baptiste Vincourt a , Lamice Habib b , Patrick Netter a , Hélène Greige-Gerges b , Jacques Magdalou a a UMR 7561 CNRS-Université Lorraine, School of Medicine, 9 Avenue de la forêt de Haye, BP 184, F-54505 Vandœuvre-lès-Nancy, Cedex, France b Bioactive Molecules Research Group, Faculty of Sciences-2, Lebanese University, Jdaidet el-Matn, Lebanon h i g h l i g h t s ◮ Cucurbitacins I, D and E cytotoxicity toward chondrosarcoma was investigated. ◮ All cucurbitacins showed a very strong cytotoxicity and induced apoptosis. ◮ Cucurbitacins biotransformation in vitro in human liver was investigated. ◮ Cucurbitacin were glucuronidated by several UGTs isoforms at a very low extent. ◮ Cucurbitacin E was hydrolyzed by microsomal esterases leading to cucurbitacin I. a r t i c l e i n f o Article history: Received 12 October 2012 Received in revised form 16 November 2012 Accepted 19 November 2012 Available online 27 November 2012 Keywords: Cucurbitacin Glucuronidation Sulfation Hydroxylation Cytotoxicity Chondrosarcoma a b s t r a c t Cucurbitacins are a class of natural compounds known for their numerous potential pharmacological effects. The purpose of this work was to compare the cytotoxicity of three cucurbitacins I, D, E on the chondrosarcoma SW 1353 cancer cell line and to investigate their biotransformation in man. Cucur- bitacins I and D showed a very strong cytotoxicity, which was higher than that of cytochalasin D, used as a drug reference. Almost 100% of the cells were apoptotic as observed by DNA fragmentation (TUNEL assay) after 12 h with cucurbitacins I and D (1 M) and cucurbitacin E (10 M). In terms of IC 50 values, cucurbitacins I and E presented a higher toxicity compared to that of cucurbitacin D (MTT assay). Cucur- bitacin E was readily hydrolyzed by human hepatic microsomes, leading to cucurbitacin I (K m 22 M, V max 571 nmol/mg proteins/min). On the other hand, the three cucurbitacins were hydroxylated at a very low extent, but they were sulfated and glucuronidated. In terms of V max /K m , the cucurbitacin E was the best substrate of UDP-glucuronosyltransferases. This study shows that cucurbitacins I, D and E present a potent cytotoxic activity toward the chondrosarcoma SW 1353 cell line and are metabolized as sulfate and glucuronide conjugates. © 2012 Elsevier Ireland Ltd. All rights reserved. 1. Introduction Cucurbitacins are a family of highly oxygenated triterpenoids characterized by tetracyclic cucurbitane nucleus skeleton: the 19- (10 → 9)-abeo-10-lanost-5-ene (Chen et al., 2005; Seger et al., Abbreviations: FCS, fetal calf serum; ITS, insulin, tansferrin and sodium selen- ite; MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide; NADPH, nicotinamide adenine dinucleotide phosphate; TdT, terminal deoxynucleotidyl transferase; UDP, uridine diphosphate; UDPGA, uridine 5 ′ -diphosphoglucuronic acid. ∗ Corresponding author. Tel.: +33 383 68 54 23; fax: +33 383 68 54 09. E-mail addresses: suziabbas@yahoo.com (S. Abbas), Jean-Baptiste.Vincourt@medecine.uhp-nancy.fr (J.-B. Vincourt), lamice.habib@yahoo.fr (L. Habib), patrick.netter@medecine.uhp-nancy.fr (P. Netter), hgreige@ul.edu.lb (H. Greige-Gerges), Jacques.Magdalou@medecine.uhp-nancy.fr (J. Magdalou). 2005). They are natural compounds found mainly in Cucurbitaceae and in large varieties of plants families (Chen et al., 2005; Dirr et al., 1986). Cucurbitacin synthesis in plants is initiated by the cucurbitadienol synthase (Shibuya et al., 2004). The primary cucur- bitacins synthesized are cucurbitacins E and B that possess an acetyl function at C25 (Fig. 1) (Gry et al., 2006). The other cucurbitacins are produced due to several metabolic reactions as hydrogena- tion by cucurbitacin  23 -reductase, deacetylation by cucurbitacin acetylesterases, hydroxylation, dehydrogenation and isomeriza- tion reactions (Dirr et al., 1986; Gry et al., 2006; Schabort and Teijema, 1968). Those reactions lead to more than 20 different species of cucurbitacins that differ from each other by their hydrox- ylation at C-2, -3, -19, -24, the presence of a double bond between C-1 and C-2 or between C-23 and C-24, the acetylation of the C-25 hydroxyl group and the presence of a ketone function at C-3 (Chen et al., 2005). 0378-4274/$ – see front matter © 2012 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.toxlet.2012.11.014