Isolation of quinone reductase (QR) inducing agents from ginger rhizome and their in vitro anti-inflammatory activity Feng Li a,b , Yongli Wang a , Kirk L. Parkin b , Viriya Nitteranon b , Jin Liang a , Wenjian Yang a , Ying Li b , Guodong Zhang b , Qiuhui Hu a, ⁎ a College of Food Science and Technology, Nanjing Agricultural University, Nanjing 210095, People's Republic of China b Department of Food Science, University of Wisconsin-Madison, 1605 Linden Drive, Madison, WI 53705, United States abstract article info Article history: Received 27 February 2011 Accepted 8 April 2011 Keywords: Ginger rhizome Quinone reductase [6]-Dehydroshogaol Inflammation To investigate the potential activity of ginger rhizome extracts to induce quinone reductase (QR), we performed bioactivity-guided fractionation using a murine hepatoma cell (Hepa 1c1c7) bioassay. Anti- inflammatory effects were then studied utilizing lipopolysaccharide (LPS)-stimulated mouse macrophage (RAW 264.7) cells. An ethyl acetate-partitioned fraction from ethanolic extract, rich in both QR inducing potency and anti-inflammatory activity, was subjected to repeated silica gel column and preparative thin layer chromatography to yield three compounds. The three isolated compounds were [6]-shogaol, 1-dehydro- [6]-gingerdione and hexahydrocurcumin. [6]-Dehydroshogaol, a minor component in ginger rhizome, was chemically synthesized and used for comparison in the subsequent bioassay based on its excellent QR inducing potency. Results showed that [6]-dehydroshogaol had the highest ability to induce QR activity (CD = 9.23 ± 0.22 μM), followed by 1-dehydro-[6]-gingerdione (CD = 13.24 ± 0.45 μM), and then hexahy- drocurcumin (CD = 68.81 ± 3.90 μM). Increasing QR activity in induced cells was associated with elevated expression of NQO-1 protein as confirmed by Western blot. [6]-Dehydroshogaol, [6]-shogaol and 1-dehydro- [6]-gingerdione were also potent inhibitors of nitric oxide (NO) synthesis in activated macrophages. Their IC 50 values ranged from 5.80 ± 1.27 to 25.06 ± 4.86 μM. Hexahydrocurcumin exhibited the weakest inhibitory effect (IC 50 = 304.76 ± 54.80 μM). These findings contribute to our theoretical understanding of the potential beneficial effects of consuming ginger as food and/or dietary supplement. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Cancer chemoprevention has been defined as the use of dietary and pharmacological intervention with specific natural or synthetic agents, designed to prevent, suppress, or reverse the process of carcinogenesis before the development of malignancy (Hong & Sporn 1997). Recently, increasing evidence based on in vitro and in vivo investigations have been linked to a decreased cancer risk with the consumption of certain dietary photochemicals (Bachmeier et al. 2010; Russo 2007). Among the multiple mechanisms underlying the chemopreventive potential of these constituents, xenobiotic- transforming and antioxidant defense systems are widely viewed as affording protection from cancer through the detoxification of potential carcinogens and mitigation of oxidative stress (Calabrese et al. 2008). The induction of phase II enzymes was proposed as a major mechanism of cellular protection against the toxic and reactive chemical species (Begleiter et al. 1997), and neoplastic effects of carcinogens (Wattenberg 1992). The elevation of phase II detoxifica- tion enzymes through the antioxidant response element (ARE) by dietary factors is considered more beneficial than coordinative induction of both phase I (cytochrome P450s) and phase II enzymes. Other ARE-encoded enzymes include glutathione and glucuronide conjugating enzymes, multidrug resistance protein, antioxidant defense agents such as hemeoxygenase-1 (HO-1), thioredoxin reductase, sirtuins, glutamate cysteine ligase, and several heat shock proteins (Russo 2007). Talalay (1989) and Wattenberg (1992) have reported that induction of phase II detoxification enzymes, which can modulate the threshold for chemical carcinogenesis and thereby increase cellular resistance to carcinogen exposure, was correlated with protection against chemical-induced carcinogenesis in animal models (Song et al. 1999). This was demonstrated in the stage of promotion as well as initiation (Gills et al. 2006). The regulatory regions of inducible ARE genes are activated upon binding of the nuclear factor E2-related protein 2 (Nrf2) transcription factor. Nuclear translocation of Nrf2 has been shown to be essential in the up- regulation of these protective genes as a response to oxidative stress, electrophiles, and some phytochemicals (Eggler et al. 2008). QR (NAD(P)H: quinone reductase, EC1.6.99.2), one of the important components of phase II detoxification enzyme systems, catalyzes the two-electron reductions of a variety of quinone Food Research International 44 (2011) 1597–1603 ⁎ Corresponding author. Tel./fax: + 86 25 84399086. E-mail address: qiuhuihu@njau.edu.cn (Q. Hu). 0963-9969/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2011.04.010 Contents lists available at ScienceDirect Food Research International journal homepage: www.elsevier.com/locate/foodres