Quantification of Antioxidants in Medicinal Plants and Foodstuffs Using Ce(IV) with Indigo Carmine as Chromogenic Probe
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Quantification of Antioxidants in Medicinal Plants and Foodstuffs Using Ce(IV) with Indigo Carmine as Chromogenic Probe Padmarajaiah Nagaraja & Anandamurthy Suma & Narayana Aradhana & Anantharaman Shivakumar & Krishnegowda Avinash & Honnur Krishna
Received: 14 June 2011 / Accepted: 2 November 2011 / Published online: 19 November 2011 # Springer Science+Business Media, LLC 2011
Abstract A simple, novel, sensitive and diversely applicable antioxidant assay method has been developed for the determination of total antioxidant capacity of some foodstuffs and medicinal plants. The method is based on the oxidation of antioxidants by a known amount of Ce(IV) sulphate under slightly acidic medium and subsequently allowing the unreacted Ce(IV) to react with a known amount of Indigo Carmine dye followed by measuring the unreacted blue-coloured Indigo Carmine dye solution at λmax =610 nm at room temperature. The antioxidant power was evaluated in terms of trolox equivalent antioxidant capacities and compared with those of ferric-reducing antioxidant power (FRAP–1.10 phenanthroline), Cu(II) reduction assay using bathocuproinedisulfonic acid disodim salt and 2, 2-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid methods. A good correlation (R2 =0.926) was found with the classical spectrophotometric FRAP assay. The proposed method is reproducible and successfully applied to assess the total antioxidant capacities in foodstuffs, vegetables and medicinal plants. The obtained results were compared with reference methods. Interference from other substances was also studied. Keywords Antioxidant . Spectrophotometry . Ce(IV) . Indigo Carmine dye . Trolox equivalent antioxidant capacities (TEAC)
P. Nagaraja (*) : A. Suma : N. Aradhana : A. Shivakumar : K. Avinash : H. Krishna Department of Studies in Chemistry, University of Mysore, Manasagangotri, Mysore 570006 Karnataka, India e-mail: [email protected]
Introduction Free radicals are unstable species because they have unpaired electron and seek stability through electron pairing with biological macromolecules (Winrow et al. 1993). When free radicals are in excess, they overwhelm protective enzymes such as superoxide dismutase, catalase, and peroxidase and cause cell destruction by oxidizing membrane lipids, proteins, DNA and enzymes, thus shutting down the cellular respiration (Colbert and Decker 1991; Shahidi et al. 1992). Antioxidants are vital in combating these free radicals, which otherwise damage human cell membranes under ‘oxidative stress’ conditions causing cancer, atherosclerosis, ageing and inflammatory diseases (Braca et al. 2002; Maxwell 1995). Dietary antioxidants, polyphenolic compounds, vitamin E, vitamin C and β-carotenoids are considered to be effective nutrients in the prevention of these oxidative stress-related diseases (Ames et al. 1995; Kaur and Kapoor 2001). Plants and foodstuffs are treasure houses of antioxidant constituents like polyphenols, vitamins, carotenoids and minerals. Natural antioxidants such as plant flavonoids are increasingly attracting attenti
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