RESUMEN
BACKGROUND: Walnut (Juglans regia L.), that belongs to the Juglandaceae family, is one of the nuts commonly found in Chinese diets. Researchers had obtained peptides from walnut protein hydrolysates, and these peptides exhibited the high antioxidant activities. The objective of this study was to develop a simple and convenient method for a facile and reproducible preparation of antioxidant peptides from walnut protein hydrolysates. RESULTS: Walnut proteins were extracted from walnut kernels using continuous countercurrent extraction process, and were separately hydrolyzed with six types of proteases (neutrase, papain, bromelain, alcalase, pepsin, and pancreatin). Then, hydrolysates were purified by ultrafiltration. The yields and purity of the peptides prepared using neutrase and papain were 16 and 81 % at least, respectively, higher than others, and had low molecular weight, 99 % of which were less than 1500 Da. Furthermore, the bioassay indicated that the two peptides exhibited the high antioxidant activities in the DPPH (IC50 values: 59.40 and 31.02 µg/mL, respectively), ABTS (IC50 values: 80.36 and 62.22 µg/mL, respectively), and superoxide radical scavenging assay (IC50 values: 107.47 and 80.00 µg/mL, respectively). CONCLUSIONS: The method combines the advantages of generality, rapidity, simplicity, and is useful for the mass production of walnut peptides.Graphical AbstractPreparation of antioxidant peptides from walnut (Juglans regia L.) protein hydrolysates.
RESUMEN
Five known compounds, 6'-methylglucuronide-5-hydroxy-chromone (1), ethyl α-d-glactopyranoside (2), neoechinulin A (3), 9,12,13-trihydroxyoctadeca-10(E),15(Z)-dienoic acid (4) and phellopterin (5), were isolated from water extract of Cyrtomium fortumei (J.) Smith. Compounds 1-5 were isolated from this genus for the first time, and all the compounds were evaluated in vitro against a panel of human cancer cells by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. Among them, compounds 3 and 4 exhibited significant cytotoxic activities, with IC50 values of 15.2 and 18.3 µg/mL on MGC-803 cells, respectively.