br Conclusion RSP can be obtained

Conclusion RSP can be obtained from the enzymatic hydrolysis of rapeseed protein, and can be fractionated into four fractions with various molecular masses by gel filtration on a Sephadex G-25 column. Fraction RSP-4 revealed the highest ABTS radical-scavenging activity and ACE-inhibiting capacity. Meanwhile, the amino I-BET-762 sequence of RSP-4 was identified as PFDSYFVC, with a molecular mass of 977D. Based on these studies, RSP has high potential to develop as a valuable antioxidant peptide for food additives. However, further structural analysis of RAH still needs to be conducted.
Acknowledgements This work was finically supported by the National Natural Science Foundation of China (Nos. 30800767 and 31271979), and the Opening Foundation of Large-scale Equipment in Tianjin University.
Introduction Flavonoids are a large group of naturally occurring phenolic constituents, ubiquitously present in edible plants, vegetables and fruits. Epidemiological evidence suggests that consumption of foods and beverages rich in flavonoids correlate with lower risk of various diseases, including certain cancers, cardiovascular diseases and oxidative stress-related diseases [1]. More than 6000 varieties of flavonoids have been identified, among them quercetin (abundant in onion, apple, broccoli and berries) and catechin (abundant in tea) are the most common and widely consumed flavonoids [2]. Onion (Allium cepa L.), a widely consumed vegetable, is a good source of dietary phytochemical (organosulphur compounds and flavonoid especially quercetin) with proven antioxidant properties and ability to modulate the detoxification systems [3,4]. Various scientific reports have confirmed its functional properties which include free radical scavenging activities, immune stimulation, cardioprotective effects (by lowering serum cholesterol and blood pressure), anti-cancer, and anti-infectious properties [5]. Various degenerative and metabolic diseases such as diabetes, atherosclerosis, cancer and aging are known to lead toward oxidative stress [6]. In recent years, there is renewed interest toward study of plants and their isolated compounds for the prevention of diseases and diverse pathological conditions by offering protection against cellular damage and oxidative stress [7].
Materials and methods
Results A significant (P<0.05) reduction in body weight was observed after four weeks in mercuric chloride treated rats (Fig. 1). All the groups were studied for the plasma antioxidant capacity by FRAP assay. Treatment with either onion extract, catechin or quercetin increased the antioxidant potential of the plasma (P<0.05) and (P<0.01) with respect to control (Fig. 2A), however, the antioxidant potential of plasma was significantly (P<0.001) reduced in rats treated with HgCl2 (Fig. 2B). Treatment of HgCl2 challenged rats with either onion extract, quercetin or catechin significantly (P<0.01) improved the antioxidant potential of the plasma compared to HgCl2 treated group (Fig. 2B). At the end of the fourth week, the level of MDA was significantly increased in the HgCl2 group compared with the control (P<0.001) (Fig. 3B), and, in contrast, no statistically significant change was observed in rats treated with either onion, catechin or quercetin (Fig. 3A). The MDA level was significantly decreased in erythrocytes at the end of the fourth week in the onion+HgCl2, catechin+HgCl2 group and quercetin+HgCl2 group compared with the HgCl2 group (P<0.05) and (P<0.001) (Fig. 3B). Treatment with onion extract and catechin caused slight increase (13.92% and 20.70%) in GSH level (P<0.05), however, treatment with quercetin resulted in significantly higher GSH level (37.02%) as compared to control (P<0.001) (Fig. 4A). HgCl2 treatment significantly depleted erythrocyte GSH as compared to control (P<0.0001) (Fig. 4B). Co-treatment of onion extract, catechin and quercetin with HgCl2 significantly (P<0.001) improved the GSH level as compared to HgCl2 group (Fig. 4B).