Antioxidant activity of grape seed (Vitis vinifera) extracts on peroxidation models in vitro

Abstract

Antioxidant-rich fractions were extracted from grape seeds (Vitis vinifera) using various solvents, such as acetone, ethyl acetate, methanol and mixtures of different solvents, such as ethyl acetate (EtOAc) and water in 9:1, 17:3 and 4:1 ratios. The antioxidant activity of the extracts was evaluated using a β-carotene-linoleate model system and linoleic acid peroxidation method. At 100 ppm concentration, various extracts showed 65–90% antioxidant activity. Mixtures of EtOAc and water at different concentrations exhibited more antioxidant activity than other extracts. These extracts also showed good reducing power, at 500 μg/ml concentration, by the potassium ferricyanide reduction method. Grape seed extracts may be exploitable for the preservation of food products as well as for health supplements and nutraceuticals.

Introduction

Lipid peroxidation is one of the major reasons for deterioration of food products during processing and storage. The addition of antioxidants is a method of increasing shelf life, especially of lipids and lipid-containing foods. Synthetic antioxidants, such as butylated hydroxyanisole (BHA) and butylated hydroxytolune, have restricted use in foods as these synthetic antioxidants are suspected to be carcinogenic (Madahavi & Salunkhe, 1995). Therefore, the search for natural antioxidants, especially of plant origin, has greatly increased in recent years (Loliger, 1991).

Grape (Vitis vinifera) is one of the world's largest fruit crops, which approximates an annual production of 58 million metric tons (FAO, 1997). Phenolics in grapes and red wines have been reported to inhibit human low-density lipoprotein (LDL) oxidation in vitro (Frankel et al., 1995, Teissedre et al., 1996). Grape seeds are a rich source of monomeric phenolic compounds, such as (+)-catechins, (−)-epicatechin and (−)-epicatechin-3-O-gallate, and dimeric, trimeric and tetrameric procyanidins, and these compounds act as antimutagenic and antiviral agents (Saito, Hosoyama, Ariga, Kataoka & Yamaji, 1998). There are reports of the possible use of phenolics in grapes in preventing atherosclerosis (Kovac & Pekic, 1991). Recognition of such health benefits of catechins and procyanidins has led to the use of grape seed extract as a dietary supplement (Laparra, Michaud & Masquelier, 1979) Phenolic compounds, extracted from twelve different varieties of grapes, showed antioxidant activity toward LDL oxidation in vitro (Mayer, Ock-Sook, Person, Waterhouse & Franke, 1997). Studies have been reported of the procyanidin composition of grape seeds (Lee & Jaworski, 1987). The predominant compounds reported are hexamers, but only the structures of some dimer and trimer procyanidins and their acylated derivatives have been elucidated. All of the acylated procyanidins found in grape seeds are esters of gallic acid (Lee & Jaworski, 1990). Teresa, Yolanda, Julian and Celestino (1992) have reported 17 chemical constituents in V. vinifera (Tintal del pais) grape seeds. The major compounds are (+)-catechin (11%), epicatechin-(4β→8)-epicatechin (dimer B2) (6%), (−)-epicatechin (10%), epicatechin 3-O-gallate-(4β→8)-catechin (B1-3-O-gallate) (7%) and (−)-Epicatechin-3-O-gallate (9%). Fuleki and Ricardo da Silva (1997) have reported monomers of (+)-catechin, (−)-epicatechin and (−)-epicatechin-3-O-gallate, 14 dimeric, 11 trimeri procyanidins and one tetrameric procyanidin from grape seeds. Substantial quantities of highly polymerised procyanidins are also present in the grape seeds. It has been found that 55% of the procyanidins in grape seeds consist of more than five monomer units. The objectives of this study were to prepare an antioxidant-rich fraction of grape seed extract and to evaluate its antioxidant activity using a β-carotene-linoleate model system and linoleic acid peroxidation method.