Natural Product Research Vol. 23, No. 13, 10 September 2009, 1240–1251 Antioxidant activity of Hypericum hookerianum Wight and Arn H. Raghu Chandrashekhar a * , P. Venkatesh b , S. Ponnusankar b and P. Vijayan b a Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical Sciences, Manipal 576104, Karnataka, India; b Department of Pharmaceutical Biotechnology, J.S.S. College of Pharmacy, Ooty 643001, Tamil Nadu, India (Received 4 June 2008; final version received 13 March 2009) Methanolic extracts of leaf, root, flower and aerial parts of Hypericum hookerianum were assessed for in vitro antioxidant activity using eight different models. Total antioxidant capacity, phenol and flavanol content of the extracts were determined to correlate between their antioxidant activity and constituents present therein. Results of in vitro antioxidant study suggest that extracts from leaf and flower have strong antioxidant potential. Leaf extract (100 & 200 mg kg 1 b.w. p.o.) that showed maximum activity was selected for in vivo antioxidant studies using a CCl 4 -intoxicated rat model. The effects of extracts on lipid peroxidation (LPO), superoxide dismutase (SOD) and catalase (CAT) in serum and liver homogenate were analysed. CCl 4 treatment caused a significant increase in the level of CAT and SOD and a significant decrease in the level of LPO in a dose-dependent manner when compared to CCl 4 treated control. The results indicate the strong antioxidant nature of H. hookerianum leaf extract. Keywords: Hypericum hookerianum; free radicals; CCl 4 1. Introduction Cell damage caused by free radicals is a major contributor to aging and degenerative diseases such as cancer, cardiovascular diseases, cataracts, immune system decline and brain dysfunction (Sies, Stahl, & Sundquist, 1992). Free radicals have been implicated in the pathogenesis of at least 50 different diseases. In recent times natural products and drugs such as antioxidant agents have received much attention, and herbal medicine has been improved in developing countries as an alternative solution to health problems (Kalt, Forney, Martin, & Prior, 1999). Hypericum is a large genus of herbs or shrubs comprising more than 1000 species (Cakir et al., 2003). Many of the Hypericum species are being used as traditional medicinal plants in different parts of the world. About 20 different species occur in India, including a few cultivated in gardens (Anonymous, 1962). Several species belonging to Hypericum, namely, H. perforatum (Luo, Sun, Mao, Lu, & Tan, 2004), H. hyssopifolium (Cakir et al., 2003), H. empetrifolium (Couladis et al., 2002), H. rumeliacum (Couladis et al., 2002), H. perfoliatum (Couladis et al., 2002), H. jovis (Athanasas et al., 2004), etc. are reported to *Corresponding author. Email: raghushekhar@gmail.com ISSN 1478–6419 print/ISSN 1029–2349 online ß 2009 Taylor & Francis DOI: 10.1080/14786410902885070 http://www.informaworld.com Downloaded By: [Raghu Chandrashekhar, H.] At: 06:10 7 September 2009