Thirteen-week repeated dose toxicity of Siraitia grosvenori extract in Wistar Hannover (GALAS) rats

Abstract

Siraitia grosvenori extract has been used as a food additive. As a part of the safety assessment of the extracts, a 13-week repeated dose toxicity study was performed in Wistar Hannover (GALAS) rats. Male and female rats were divided into five groups consisting of eight animals each and given diet containing 0%, 0.04%, 0.2%, 1%, and 5% of S. grosvenori extract for 13 weeks. During the experiment, no deaths were observed in any groups, and there were no remarkable changes in general appearance, body weight, food and water consumption, hematological and serum biochemical parameters, organ weight and histopathological findings between the control and treated groups. On the basis of these data, the no-observed-adverse effect level (NOAEL) of S. grosvenori extract in Wistar Hannover rats was considered to be 5% (2520 mg/kg/day in males and 3200 mg/kg/day in females) or more.

Introduction

Luo Han Kuo (Siraitia grosvenori), formerly called Momordica grosvenori (a member of the Curcubitaceae), is an intensely sweet fruit and has been cultivated in a restricted area of the southern part of China, Guangxi Province (Kasai et al., 1989). Since the major components of this plant are mogroside V and 11-oxo-mogroside V that are 400 times sweeter than sucrose (Matsumoto et al., 1990), this plant has been used as a sweet beverage. This fruit has been also traditionally used as folk medicine for the treatment of pharyngitis or pharyngeal pain as well as antitussive medicine in China and Japan (Kasai et al., 1989). Because of the efficacy of this fruit, the heated and dried fruit or the extract that was extracted with water or ethanol has been exported from the China to southeast Asia, Japan and the United States of America (Konoshima and Takasaki, 2002), and this extract has been used as a food additive in Japan. Recently, much attention has been paid on the cancer chemopreventive and antioxidant effects of this extract, and several experimental studies to demonstrate such effects have been reported (Konoshima and Takasaki, 2002, Takeo et al., 2002, Shi et al., 1996, Takasaki et al., 2003).

With respect to the toxicity of this extract, it has been established by the contract studies of the Ministry of Health, Labor and Welfare (MHLW) of Japan that LD50 of this extract is more than 2000 mg/kg body weight by gavage for rats (Unpublished data). In addition, the genotoxicity was confirmed by the MHLW to be negative in Ames test, in vitro chromosome aberration study and in vivo micro-nucleus test (Unpublished data). Regarding the repeated dose toxicity studies, a 90-day toxicity study in F344 rats was performed in Japan, and the data are available in Japanese as a report submitted to the MHLW of Japan but not published in academic journals. In this report, it was described that the highest dose was set as 2% in diet in spite of the fact that there were no remarkable changes in the highest dose group of the preliminary dose-range finding study where rats received diet containing 5%, 2%, 1%, or 0% S. grosvenori extract for 4 weeks. In addition, since the purity of this extract was extremely low, the toxicity of this extract could not be adequately evaluated. Furthermore, histopathological examinations were performed on the limited numbers of animals of some of the treated and control animals. In accordance with the request from the MHLW as a part of a comprehensive safety assessment of the existing food additives, a 13-week repeated toxicity study was conducted to clarify the repeated dose toxicity of S. grosvenori extract in the present study.