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To screen, prepare, identify, and evaluate the activities of natural antioxidants for treating chronic diseases caused by oxidative stress. Two algal proteins, namely ZD10 and ZD60, precipitated with 10 and 60% (NH4)2SO4 were extracted from red algae Eucheuma cottonii (E. cottonii) and hydrolyzed using five proteolytic enzymes. The results showed that ZD60 played the most significant role in the enhancement of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH⋅) scavenging activity (25.91 ± 0.24%) among all protein hydrolysates. Subsequently, six antioxidant peptides (EP1-EP6) were isolated from the papain hydrolysate of ZD60 by ultrafiltration and chromatography methods. Their amino acid sequences were identified as Thr-Ala (EP1), Met-Asn (EP2), Tyr-Ser-Lys-Thr (EP3), Tyr-Ala-Val-Thr (EP4), Tyr-Leu-Leu (EP5), and Phe-Tyr-Lys-Ala (EP6) with molecular weights of 190.21, 263.33, 497.55, 452.51, 407.51, and 527.62 Da, respectively. Of which, EP3, EP4, EP5, and EP6 showed strong scavenging activities on DPPH⋅, hydroxyl radical (HO⋅), and superoxide anion radical (O- 2⋅). Moreover, EP4 and EP5 could significantly protect human umbilical vein endothelial cells (HUVECs) from H2O2-induced oxidative damage by increasing the levels of antioxidant enzyme systems including superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to reduce the levels of reactive oxygen species (ROS) (60.51 and 51.74% of model group) and malondialdehyde (MDA) (75.36 and 64.45% of model group). In addition, EP4 and EP5 could effectively inhibit H2O2-induced apoptosis by preventing HUVECs from early apoptosis to late apoptosis. These results indicated that the antioxidant peptides derived from E. cottonii, especially EP4 and EP5, could serve as the natural antioxidants applied in pharmaceutical products to treat chronic cardiovascular diseases caused by oxidative damage, such as coronary heart disease, atherosclerosis, etc.

Alcalase was screened out for hydrolyzing the swim bladder proteins of miiuy croaker (Miichthys miiuy) from five proteases using hydroxyl radical scavenging assay, and its optimal hydrolysis conditions were be determined as time 3.5 h, temperature 55 °C, pH 9.5, solid-liquid ratio 1:5, and enzyme dose 2.5%. Ten new antioxidant peptides were isolated from SMAH using ultrafiltration and consecutive chromatography, and their sequences were identified as FYKWP, FTGMD, GFEPY, YLPYA, FPPYERRQ, GFYAA, FSGLR, FPYLRH, VPDDD, and GIEWA. FPYLRH and GIEWA exhibited strong scavenging activities on hydroxyl radical (EC50 0.68 mg/mL and 0.71 mg/mL for FPYLRH and GIEWA, respectively), DPPH radical (EC50 0.51 mg/mL and 0.78 mg/mL for FPYLRH and GIEWA, respectively), and superoxide anion radical (EC50 0.34 mg/mL and 0.30 mg/mL for FPYLRH and GIEWA, respectively). In addition, FPYLRH and GIEWA could be effectively against lipid peroxidation in the β-carotene linoleic acid and in the linoleic acid emulsion system.

Eight novel and three known antioxidant peptides isolated from protein hydrolysate of Moringa oleifera seeds, using ultrafiltration, anion-exchange chromatography, gel filtration chromatography and reversed phase high performance liquid chromatography (RP-HPLC). The novel peptides were identified as Gly-Tyr (GY), Pro-Phe-Glu (PFE), Tyr-Thr-Arg (YTR), Phe-Gly (FG), Gln-Tyr (QY), Ile-Asn (IN), Ser-Phe (SF), Ser-Pro (SP), and the known peptides were identified as Tyr-Phe-Glu (YFE), Ile-Tyr (IY) and Leu-Tyr (LY), respectively, using protein amino acid sequence analyzer and electrospray ionization-mass spectrometry. All the eleven peptides exhibited strong scavenging activities on 2,2-Diphenyl-1picrylhydrazyl radical (DPPH·) (EC50 2.28, 1.60, 1.77, 2.15, 0.97, 1.30, 0.75, 0.91, 1.21, 0.79, and 1.37 mg/L, respectively) and 2,2-azino-bis (3-ethylbenzothia zoline-6-sulfonic acid) diammonium salt radical (ABTS·+) (EC50 1.03, 0.84, 0.95, 0.65, 0.37, 0.54, 0.33, 0.36, 0.67, 0.32 and 0.38 mg/mL, respectively). In addition, SF and QY showed protective effects on oxidative damage Chang liver cells induced by H2O2, and the contents of aspartate aminotransferase (ALT), alanine aminotransferase (AST) and malondialdehyde (MDA) decreased with the increasing concentrations of SF and QY. Furthermore, SF and QY could significantly increase the levels of superoxide dismutase (SOD) and catalase (CAT), thereby effectively scavenge reactive oxygen species (ROS) in H2O2-induced oxidative damaged Chang liver cells (P

Doxorubicin (DOX) is a commonly used anthracycline in treatments of leukemia, lymphoma and breast cancer in humans and has been limited by its cardiotoxicity, which is manifested congestive heart failure in the worst condition. The present study showed that the marine carotenoid of fucoxanthin could exert cardioprotective effect against the DOX-induced injury in ICR mice. And then, the protective effects and mechanisms of fucoxanthin on DOX-induced injury of neonatal rat cardiomyocytes were investigated. The results demonstrated that fucoxanthin significantly reduced mice toxic death triggered by DOX. The protective effects were also showed by the suppression of apoptotic cell death in cardiomyocytes. Further study revealed that fucoxanthin-produced suppression of MAPK activated by DOX was involved in the cardioprotection. The findings confirmed the cardioprotective effect of fucoxanthin against DOX-induced cardiotoxicity by protecting myocardial cells from lipid peroxidation and apoptosis, which would likely result in an increased therapeutic window of DOX in cancer therapy.