Antioxidant and Hypolipidemic Potential of Peptides from Broccoli Stems and Leaves

To isolate bioactive broccoli peptides, crude proteins were flocculated from heated juice of broccoli stems and leaves and then hydrolyzed by proteases. Different proteases yielded different peptides with a significant effect on the bio-activities of broccoli peptides. Antioxidant activity of the broccoli peptides was investigated by measuring their DPPH (1,1-diphenyl-2-picrylhydrazyl) radicals scavenging action in comparison to native antioxidants, reduced glutathione (GSH) and soybean peptides. Broccoli peptides (obtained by Neutrase (R) hydrolysis) at 5.0 mg/mL exhibited 72.8% of radicals scavenging rates, resembling GSH at 1.0 mg/mL (72.1%), and was 2.8 times than that of soybean peptides at 5.0 mg/mL (25.7%). Subsequently, the hypolipidemic activities were measured by oral gastric gavage of broccoli peptides in hyperlipemic golden hamster. Treatment with broccoli peptides (obtained by papain hydrolysis) significantly decreased the serum TC and LDL-C levels (P < 0.01) in experimental rats. The constitution of amino acid and the distribution of molecular weight analysis showed broccoli peptides contained sixteen amino acids and a great percentage of low molecular weight peptides (<1 kDa, 77.67%). By analyzing the amino acid compositions and bio-activities, our results indicate the high nutritive value and possible applications of broccoli peptides for human health.