Antioxidant and chelating activity of Jatropha curcas L. protein hydrolysates

Abstract

Jatropha curcas L., a member of the Euphorbiaceae family, is a drought-resistant small tree of great economic importance in developing countries because of its several industrial and medicinal uses.1,2 The seeds contain around 600 g kg−1 oil and 300 g kg−1 protein.3 The seed oil is used for biodiesel production and for manufacturing cosmetics, but the protein-rich defatted meal resulting from oil extraction is mostly wasted. This is so because of the presence of toxic phorbol esters in this material.3 However, non-toxic genotypes which do not contain phorbol esters have been reported in Mexico.1 The concentration of antinutritional and toxic components in the defatted seed meal is reduced during the preparation of J. curcas protein isolates.4 These protein isolates are a good substrate for the production of hydrolysates with improved functional and nutritional properties, which facilitates the revalorization of numerous oilseeds and grain legumes.5 In addition, protein hydrolysates are a source of bioactive peptides, which are shortchain peptides with beneficial biological activities which are released from food proteins during hydrolysis.6 For example, bioactive peptides with antihypertensive, immunomodulatory, opioid, antioxidant, hypocholesterolemic, and metal-chelating activity have been described.6,7 Oxidative damage due to generation of reactive oxygen species has been related to a variety of diseases, including cancer, cardiovascular disease, and neurodegenerative diseases. Excessive production of oxygen reactive species, and/or decreased antioxidant defenses, lead to damage to various cell components, including lipids, proteins and nucleic acids, and to blood lipoproteins. In foods, the main targets of oxidative reactions are polyunsaturated lipids. The oxidative alterations of lipids have a negative effect on flavor, texture, nutritive value, and shelf life of food products. Therefore, natural and synthetic antioxidants play a very important role in both health promotion and the conservation of foodstuffs. A variety of antioxidant peptides have been purified from various plant protein hydrolysates.8,9 Thus antioxidant peptides generated by hydrolysis of food proteins constitute a new source of functional components that could inhibit deleterious oxidative processes both in vivo and in foods. One of the mechanisms for the antioxidant effect of peptides is metal chelation, because transition metals catalyze numerous oxidative reactions.10 In addition to this,metal-chelating peptides are of interest because they can increase the bioavailability of essential trace elements such as calcium, iron, and zinc. The goal of this work was to determine the presence of antioxidant and metal-chelating peptides in J. curcas protein hydrolysates produced by treatmentwith the food-grade protease preparation alcalase. The presence of these peptides in J. curcas