Arch Pharm Res Vol 34, No 3, 455-461, 2011 DOI 10.1007/s12272-011-0314-x 455 Simultaneous Determination of Bioactive Flavonoids in Some Selected Korean Thistles by High-Performance Liquid Chromatography Nguyen Thi Phuong Thao 1 , To Dao Cuong 1 , Tran Manh Hung 1 , Je Hyun Lee 2 , MinKyun Na 3 , Jong Keun Son 3 , Hyun Ju Jung 4 , Zhe Fang 1 , Mi Hee Woo 1 , Jae Sue Choi 5 , and Byung-Sun Min 1 1 College of Pharmacy, Catholic University of Daegu, Gyeongsan 712-702, Korea, 2 College of Oriental Medicine, Dong- guk University, Gyeongju 780-714, Korea, 3 College of Pharmacy, Yeungnam University, Gyeongbuk 712-764, Korea, 4 College of Pharmacy, Wonkwang University, Jeonbuk 570-749, Korea, and 5 Faculty of Food Science and Biotechnology, Pukyoung National University, Busan 608-737, Korea (Received September 6, 2010/Revised November 15, 2010/Accepted December 16, 2010) In order to facilitate the quality control of some selected Korean thistles (Cirsii Herb), Cirsium japonicum var ussuriense, C. japonium var spinosissimum, C. setidens, C. pendulum, C. nip- ponicum, Carduus crispus, and Breea segetum, a simple, accurate and reliable high perfor- mance liguid chromatography method was developed for the simultaneous determination of the six flavonoids: luteolin 5-O-glucoside (1), luteolin 7-O-glucoside (2), hispidulin 7-O-neohes- peridoside (3), luteolin (4), pectolinarin (5), and apigenin (6), which were selected as the chem- ical markers of the thistles. Separation was achieved on an Agilent Eclipse XDB-C18 column with a gradient solvent system of 0.1% trifluoroacetic acid aqueous-methanol at a flow-rate of 1.0 mL/min and detected at 254 nm. All six calibration curves showed good linearity (R 2 > 0.991). The method was reproducible with intra- and inter-day variations of less than 6%. The recoveries were in the range of 90.01-100.05%. This analysis method was successfully utilized to quantify the six flavonoids in the 22 batches of the thistles. The results demonstrated that this method is simple, reliable and suitable for the quality control of this medicinal herb. Key words: High performance liquid chromatography (HPLC), Cirsium, Thistle, Cirsii Herb, Flavonoids INTRODUCTION Thistles, all members of the Compositae family, are perennial plants, 0.5 - 2 m in height, possessing lance- shaped, spiny-toothed leaves and white to purple flowers. The thistles grow abundantly in Korea, Japan, and China (Lee, 1979; Ganzera et al., 2005). Two hun- dred fifty species of the thistles have thus far been identified world wide, and about 10 of these species have been found in Korea (Lee, 2002). Due to various therapeutic effects, these plants have been employed in traditional folk medicine as diuretic, antiphlogistic, hemostatic, and detoxifying agents (Lee, 1966; Kim, 1984). Especially, milk thistle is one of the most popular herbal remedies used by patients with liver disease (Flora et al., 1996). This use has been support- ed by clinical trials and mechanism of action studies, so silymarin, a polyphenolic flavonoid derived from milk thistle, is now an important hepatoprotective agent (Smith et al., 2005). Silymarin is an antioxidant component which results in enhancement of cellular antioxidant defense machinery thus increasing the antioxidant potential of cells as well as protection of the liver from toxic substance (Mourelle et al., 1989; Letteron et al., 1990; Mereish et al., 1991; Luper, 1998; Bhatia et al., 1999). A great heal of research has been conducted regarding the flavonoids harbored by thistles, and a variety of activities were exhibited by these species such as cytotoxic, antimicrobial activi- ties as well as anti-haemorrhagic, antihypertensive, anti-hepatitis, and liver-enzyme-activating effects (Ishida et al., 1987; Lee et al., 1994, 2002; Park et al., 1995, 1997, 2004; Pezer et al., 2001; Nazaruk et al., 2005; Correspondence to: Byung-Sun Min, College of pharmacy, Catholic University of Daegu, Gyeongsan 712-702, Korea Tel: 82-53-850-3613, Fax: 82-53-850-3602 E-mail: bsmin@cu.ac.kr