Journal of Ethnopharmacology 108 (2006) 148–151 Ethnopharmacological communication Inhibitory effects of Tabebuia impetiginosa inner bark extract on platelet aggregation and vascular smooth muscle cell proliferation through suppressions of arachidonic acid liberation and ERK1/2 MAPK activation Dong-Ju Son a , Yong Lim a , Young-Hyun Park b , Sung-Keun Chang b , Yeo-Pyo Yun a , Jin-Tae Hong a , Gary R. Takeoka c , Kwang-Geun Lee d , Sung-Eun Lee e , Mi-Ran Kim e , Jeong-Han Kim e , Byeoung-Soo Park e,∗ a College of Pharmacy, Chungbuk National University, Cheongju 361-763, Republic of Korea b College of Natural Sciences, Soonchunhyang University, Asan 336-745, Republic of Korea c Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, 800 Buchanan Street, Albany CA 94710, USA d Department of Food Science and Technology, Dongguk University, Seoul 100-715, Republic of Korea e School of Agricultural Biotechnology, Seoul National University, San 56-1, Shillim-dong, Gwanak-gu, Seoul 151-742, Republic of Korea Received 23 February 2005; received in revised form 2 February 2006; accepted 11 April 2006 Available online 28 April 2006 Abstract The antiplatelet and antiproliferative activities of extract of Tabebuia impetiginosa inner bark (taheebo) were investigated using washed rabbit platelets and cultured rat aortic vascular smooth muscle cells (VSMCs) in vitro. n-Hexane, chloroform and ethyl acetate fractions showed marked and selective inhibition of platelet aggregation induced by collagen and arachidonic acid (AA) in a dose-dependent manner. These fractions, especially the chloroform fraction, also significantly suppressed AA liberation induced by collagen in [ 3 H]AA-labeled rabbit platelets. The fractions, especially the chloroform fraction, potently inhibited cell proliferation and DNA synthesis induced by platelet derived growth factor (PDGF)-BB, and inhibited the levels of phosphorylated extracellular signal regulated kinase (ERK1/2) mitogen activated protein kinase (MAPK) stimulated by PDGF-BB, in the same concentration range that inhibits VSMC proliferation and DNA synthesis. © 2006 Elsevier Ireland Ltd. All rights reserved. Keywords: Taheebo; Platelet aggregation; Arachidonic acid; Vascular smooth muscle cell; ERK1/2; Atherosclerosis 1. Introduction Platelet aggregation and vascular smooth muscle cell (VSMC) proliferation are essential events in the pathogenesis of vascular diseases such as thrombosis, atherosclerosis and restenosis (Sheu et al., 2004). A number of peptide growth factors, such as platelet derived growth factor (PDGF), released from platelets and VSMCs in response to vascular injury are known to play an important role in stimulating VSMC proliferative response (Newby and Zaltsman, 2000). Therefore, the inhibition of platelet activation and VSMC ∗ Corresponding author. Tel.: +82 2 880 4654; fax: +82 2 873 4415. E-mail address: bsp67@snu.ac.kr (B.-S. Park). proliferation represents a promising approach for the pre- vention of cardiovascular diseases such as thrombosis and atherosclerosis. Tabebuia spp. (Bignoniaceae) are native to tropical rain forests throughout Central and South America. Taheebo has been traditionally used as an anticoagulant and to treat circulation problems. In this study, we evaluated the inhibitory properties of the fractions obtained from taheebo methanolic extract on washed rabbit platelet aggregation and cultured rat aortic VSMC proliferation in vitro. Furthermore, we examined the effects of fractions of taheebo extract on arachidonic acid (AA) liberation and extracellular signal regulated kinase (ERK1/2) mitogen activated protein kinase (MAPK) activation in order to eluci- date a possible inhibitory mechanism in platelets and VSMCs, respectively. 0378-8741/$ – see front matter © 2006 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/j.jep.2006.04.016