Novel Antioxidant Peptides from Pearl Shell Meat Hydrolysate and Their Antioxidant Activity Mechanism.

Free radicals are associated with aging and many diseases. Antioxidant peptides with good antioxidant activity and absorbability are one of the hotspots in antioxidant researches. In our study, pearl shell (Pinctada martensii) meat hydrolysate was purified, and after identification by proteomics, six novel antioxidant peptides SPSSS, SGTAV, TGVAS, GGSIT, NSVAA, and GGSLT were screened by bioinformatics analysis. The antioxidant peptides exhibited good cellular antioxidant activity (CAA) and the CAA of SGTAV (EC50: 0.009 mg/mL) and SPSSS (EC50: 0.027 mg/mL) were better than that of positive control GSH (EC50: 0.030 mg/mL). In the AAPH-induced oxidative damage models, the antioxidant peptides significantly increased the viability of HepG2 cells, and the cell viability of SGTAV, SPSSS, and NAVAA were significantly restored from 79.41% to 107.43% and from 101.09% and 100.09%, respectively. In terms of antioxidant mechanism by molecular docking, SGTAV, SPSSS, and NAVAA could tightly bind to free radicals (DPPH and ABTS), antioxidant enzymes (CAT and SOD), and antioxidant channel protein (Keap1), suggesting that the antioxidant peptides had multiple antioxidant activities and had structure-activity linkages. This study suggests that the antioxidant peptides above are expected to become new natural materials for functional food industries, which contribute to the high-value applications of pearl shell meat.

The antioxidant peptides from walnut protein hydrolysates and their protective activity against alcoholic injury.

In this study, walnut protein was hydrolyzed, separated by ultrafiltration, purified by RP-HPLC, identified by LC-MS/MS, and screened by molecular docking to finally obtain three novel antioxidant peptides HGEPGQQQR (1189.584 Da), VAPFPEVFGK (1089.586 Da) and HNVADPQR (949.473 Da). These three peptides exhibited excellent cellular antioxidant activity (CAA) with EC50 values of 0.0120 mg mL-1, 0.0068 mg mL-1, and 0.0069 mg mL-1, respectively, which were superior to that of the positive control GSH (EC50: 0.0122 mg mL-1). In the ethanol injury model, three antioxidant peptides enhanced the survival of cells treated with ethanol from 47.36% to 62.69%, 57.06% and 71.64%, respectively. Molecular docking results showed that the three antioxidant peptides could effectively bind to Keap1, CYP2E1 and TLR4 proteins. These results suggested that walnut-derived antioxidant peptides could be potential antioxidants and hepatoprotective agents for application in functional foods.

Purification and activity evaluation of novel anti-inflammatory peptides from pearl oyster (Pinctada martensii) hydrolysates.

Pearl oyster meat, a by-product of pearl production, is rich in protein, but has a low utilization rate. Our previous study showed that pearl oyster meat hydrolysates have potential anti-inflammatory activity. In this study, highly active peptides from pearl oyster meat hydrolysates were purified, identified, and extracted, and their anti-inflammatory activity was further investigated. A total of 206 peptides were identified, and three novel anti-inflammatory peptides, TWP (402.1903 Da), TAMY (484.1992 Da) and FPGA (390.1903 Da), were screened by molecular docking. The molecular docking results showed that TWP, TAMY and FPGA can bind to key regions in the cyclooxygenase-2 (COX-2) active site. Furthermore, the three anti-inflammatory peptides can effectively regulate the release of inflammatory mediators from RAW264.7 macrophages by reducing the levels of nitric oxide (NO) and pro-inflammatory cytokines (such as TNF-α, IL-6 and IL-1ß), and increasing the production of anti-inflammatory cytokine IL-10, showing great anti-inflammatory activity. This study provides a new theoretical reference for the development of functional foods or nutritional supplements with natural anti-inflammatory effects.

Rapid screening of novel tyrosinase inhibitory peptides from a pearl shell meat hydrolysate by molecular docking and the anti-melanin mechanism.

Pearls are an edible and medicinal resource with whitening activity and nutritional value in China. In the previous study, we found that the pearl shell meat hydrolysate showed dual activities of antioxidation and tyrosinase inhibition, which were similar to the activities of pearls. In this research, a pearl shell meat hydrolysate was isolated, identified and screened by molecular docking, and three peptides FLF, SPSSS and WLL with high tyrosinase inhibitory activities were obtained. The results indicated that FLF, SPSSS and WLL could effectively inhibit tyrosinase activities and the inhibition rates (1.0 mg mL-1) were 54.32%, 65.26% and 57.50%, respectively. The results of a zebrafish whitening experiment showed that the tyrosinase activities of zebrafish treated with FLF, SPSSS and WLL decreased by 75.41%, 62.87% and 64.99% (p < 0.05), respectively, and the melanin content decreased by 37.34%, 38.52% and 40.39% (p < 0.05), respectively. In a B16F10 cell whitening experiment, compared with a control group, FLF, SPSSS and WLL also showed a significant whitening effect, the tyrosinase activities decreased by 84.08%, 79.08% and 77.45% (p < 0.05), respectively, and the melanin content decreased by 42.23%, 34.37% and 34.02% (p < 0.05), respectively. Moreover, the active peptides could act on three signal pathways including Wnt/ß-catenin, MAPK and MC1R/α-MSH and significantly downregulated the expressions of the signaling factors WNT4, MITF, ß-catenin, ERK, JNK, TRP1 and TRP2 (p < 0.05). The results demonstrated that the whitening active peptides were edible natural antioxidants, tyrosinase inhibitors and skin anti-melanin agents, which could be added to functional foods as food ingredients.