Karaya root saponin exerts a hypocholesterolemic response in rats fed a high-cholesterol diet Sadia Afrose a , Md. S. Hossain a , Takaaki Maki b , Hirotada Tsujii a, ⁎ a Laboratory of Animal Biotechnology, Interdisciplinary Graduate School of Science and Technology, Shinshu University, Minamiminowa-mura, Nagano 399-4598, Japan b Matsumoto Institute of Microorganisms, Matsumoto, Japan Received 1 March 2009; revised 10 May 2009; accepted 22 May 2009 Abstract Different sources of saponins are known to have hypocholesterolemic activity with varying degrees of efficacy. We hypothesize that karaya root saponin would efficiently reduce cholesterol. The aim of this study is to examine the comparative hypocholesterolemic effect of karaya root saponin in rats fed a high-cholesterol diet. Sixty male Wister–Imamichi rats were divided into 5 groups of 12 rats each constituting of the following: control group, soybean saponin–supplemented group, karaya root saponin–supplemented group, quillaja saponin–supplemented group, and tea saponin–supplemented group. Compared with the control diet, both the karaya root– and quillaja saponin–supplemented diets significantly reduced (P b .05) serum cholesterol and atherogenic index. Karaya root saponin significantly increased the serum high-density lipoprotein cholesterol, high- density lipoprotein cholesterol/cholesterol ratio, and fecal cholesterol concentrations (P b .05). The triacylglycerol concentration was significantly reduced only in the quillaja saponin–supplemented rats (P b .05). All the tea, soybean, karaya root, and quillaja saponins significantly reduced low- density lipoprotein cholesterol, and the greatest reduction was observed with karaya root saponin. Highest fecal bile acid concentration was found with quillaja saponin, whereas highest liver bile acid concentration was observed with karaya root saponin–supplemented rats (P b .05). These results collectively suggest that karaya root saponin can efficiently reduce serum cholesterol concentration in rats. © 2009 Elsevier Inc. All rights reserved. Keywords: Karaya root saponin; Cholesterol; Triacylglycerol; Atherogenic index; Rat Abbreviations: AI, atherogenic index; CHD, coronary heart disease; HDL, high-density lipoprotein; LDL, low-density lipoprotein. 1. Introduction Coronary heart disease (CHD) is one of the most significant causes of death throughout the world. Although the occurrence of CHD is multifactorial, recent under- standing of the association between total plasma cholesterol levels and the incidence of heart disease has led to the conclusion that an increased amount of dietary cholesterol may increase the risk of CHD. During the past 4 decades, many reports have focused on how to decrease plasma lipid concentrations and the absorption of fat in the intestinal tract to reduce diet-related chronic diseases. We have previously shown that Rhodobacter capsulatus is an effective serum and egg cholesterol-lowering agent in chickens and pigs [1,2]. Rhodobacter capsulatus and Rhodopseudomonas palustris [3] reduced serum cholesterol in rats by about 28%. Despite these initiatives, there is an ongoing search for Available online at www.sciencedirect.com Nutrition Research 29 (2009) 350 – 354 www.nrjournal.com ⁎ Corresponding author. Tel.: +81 0265 77 1616; fax: +81 0265 771616. E-mail address: htsujii@shinshu-u.ac.jp (H. Tsujii). 0271-5317/$ – see front matter © 2009 Elsevier Inc. All rights reserved. doi:10.1016/j.nutres.2009.05.008