Toxicology 242 (2007) 71–79 Available online at www.sciencedirect.com Pterocarpans phaseollin and neorautenol isolated from Erythrina addisoniae induce apoptotic cell death accompanied by inhibition of ERK phosphorylation W. W¨ atjen a,∗ , A. Kulawik a , A.K. Suckow-Schnitker b,1 , Y. Chovolou a , R. Rohrig a,1 , S. Ruhl a,1 , A. Kampk ¨ otter a , J. Addae-Kyereme c , C.W. Wright c , C.M. Passreiter b a Heinrich-Heine-Universit¨ at, Institute of Toxicology, P.O. Box 101007, 40001 D¨ usseldorf, Germany b Heinrich-Heine-Universit¨ at, Institute of Pharmaceutical Biology and Biotechnology, Universit¨ atsstr. 1, 40225 D¨ usseldorf, Germany c The School of Pharmacy, University of Bradford, Richmond Road, West Yorkshire BD 71 DP, UK Received 3 August 2007; received in revised form 7 September 2007; accepted 10 September 2007 Available online 15 September 2007 Abstract The genus Erythrina (Leguminosae), consisting of over 100 different species, is distributed in tropical regions. In traditional medicine, Erythrina species are used to treat cancer, but little is known about the anticancer mechanisms. From the stem bark of Erythrina addisoniae Hutch. & Dalziel, six prenylated pterocarpans were isolated and analysed for pharmacological activity: While calopocarpin, cristacarpin, orientanol c, and isoneorautenol showed only a weak or moderate toxicity in H4IIE hepatoma cells (EC 50 -value > 25 M), the toxicity of neorautenol and phaseollin was in the low micromolar range (EC 50 -value: 1 and 1.5 M, respectively). We further focused on these two substances showing that both increased caspase 3/7 activity and nuclear fragmentation as markers for apoptotic cell death. Neorautenol (10 M, 2 h), but not phaseollin induced the formation of DNA strand breaks (comet assay). Both substances showed no effect on NF-B signalling (SEAP assay: basal activity and stimulation with TNF-), on the other hand both pterocarpans (10 M, 2h) decreased the activation of the ERK kinase (p44/p42), an mitogen activated protein kinase which is associated with cell proliferation. We conclude that the pterocarpans phaseollin and neorautenol may be responsible for the anticarcinogenic actions of the plant extract reported in the literature. Further analysis of these substances may lead to new pharmacons to be used in cancer therapy. © 2007 Elsevier Ireland Ltd. All rights reserved. Keywords: Apoptosis; Caspase; Cytotoxicity; ERK; Erythrina addisoniae; NF-B; Prenylated pterocarpans; TNF- Abbreviations: ERK, extracellular regulated protein kinase; FBS, fetal bovine serum; HPLC, high performance liquid chromatog- raphy; MTT, 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl-tetrazolium- bromide; PBS, phosphate buffered saline; ROS, reactive oxygen species; SEAP, secreted alkaline phosphatase; TNF-, tumor necrosis factor . ∗ Corresponding author. Tel.: +49 211 81 13003; fax: +49 211 81 14807. E-mail address: wim.waetjen@uni-duesseldorf.de (W. W¨ atjen). 1 This work is part of the running PhD thesis. 1. Introduction The genus Erythrina (Leguminosae), a group of more than 100 different species, is distributed in all tropical areas of the world (Krukoff and Barneby, 1974). These plant species are widely used in folk medicine to treat diverse diseases, e.g. different kinds of infections as well as inflammation of skin and mucous membranes (Ghosal et al., 1972; Cox, 1993; Saiduh et al., 2000). They are also used due to their analgesic as well as tranquiliz- 0300-483X/$ – see front matter © 2007 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.tox.2007.09.010