eng Science and Education Publishing Journal of Food and Nutrition Research 2333-1240 2014-10-27 2 11 831 838 10.12691/jfnr-2-11-12 JFNR201421112 article Ping Xiao 1 Hongzhi Huang lixiang_8182@163.com 1 Yayun Chen 1 Jianwei Chen 1 Xiang Li lixiang_8182@163.com 1 Haitao Shi 1 College of Pharmacy, Nanjing University of Chinese Medicine, Nanjing, P.R. China In this study, the antioxidant activities of alcalase-treated Radix Isatidis protein hydrolysates (RIPH) were compared during a two-stage gastrointestinal (GI) digestion in vitro. Compared with the blank, the enzymatic breakdown of the GI digests increased their 1,1-diphenyl-2-picrylhydrazyl (DPPH) (1.2-fold increase), hydroxyl (1.9-fold increase), (5.6-fold increase) in the radical scavenging activities and the reducing power (4.0-fold increase). The investigated items of RIPH consisted of the degrees of hydrolysis (DH), the compositions of amino acid, the nutritional parameters and the molecular weight distributions (MWD). The analysis of amino acid compositions of RIPH showed that essential amino acids such as isoleucine, threonine, tryptophan, valine and histidine took a high portion. The final Radix Isatidis protein hydrolysate digests (FRIPHD) contained the free amino acids of about 29.4%. Results from this study showed that RIPH is a good source of natural antioxidants that the formed peptides can resist physiological digestion in GI digestive system. http://pubs.sciepub.com/jfnr/2/11/12/jfnr-2-11-12.pdf radix isatidis protein hydrolysates; gastrointestinal digestion antioxidant activity amino acid composition