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Peptides from oysters have several bioactive functions. In this study, we identified antioxidant peptides from oysters (Crassostrea rivularis) and investigated their structure–function relationship. We used an 8 kDa molecular‐weight (MW) cut‐off membrane and semiprep reversed‐phase liquid chromatography to collect five peptides (F1–F5) and identified the highest‐abundance ion‐peak sequences AWVDY (F1), MSFRFY(F2), EPLRY(F3), RKPPWPP(F4), and YAKRCFR(F5) having MWs of 652, 850, 676, 877, and 943 Da, respectively, using ultra‐performance liquid chromatography‐quadrupole/time‐of‐flight tandem mass spectrometry. These peptides exhibited high antioxidant activities, similar to butylated hydroxytoluene, reduced glutathione, and ascorbic acid. F5 demonstrated the highest scavenging activity for DPPH radicals (IC50 = 21.75 μg/ml), hydroxyl radicals (IC50 = 18.75 μg/ml), and superoxide radicals (IC50 = 11.00 μg/ml), while F3 demonstrated the highest reducing power. Furthermore, F5 significantly protected Caco‐2 cells from H2O2‐induced oxidative damage. These results suggest that the antioxidant peptide F5 is a promising food additive that protects against oxidative damage. [ABSTRACT FROM AUTHOR]

Twelve categories of polar lipids (PLs) were quantified in round scad and hairtail during salt‐drying with electrospray ionization‐tandem mass spectrometry based on lipidomics. The major species were phosphatidylcholine (PC), phosphatidylethanolamine (PE), and ether‐linked PC (ePC), accounting for 67.8%, 11.1%, and 9.7% of total PLs in the raw round scad respectively, and 74.3%, 7.3%, and 10.9% in raw hairtail. Among the 272 and 263 kinds of PLs molecules detected in the two raw fish respectively, only 125 and 94 PLs were strongly affected by salt‐drying, including 28 PCs, 23 PEs, 21 ePCs, 9 phosphatidylinositols (PIs), 14 phosphatidylserines/phosphatidic acids/phosphatidylglycerols (PSs/PAs/PGs), 12 lysophosphatidylcholines (LPCs), 5 lysophosphatidylethanolamines (LPEs), 9 ether‐linked PEs (ePEs), 4 sphingomyelins (SMs) in round scad, and 21 PCs, 17 PEs, 15 ePCs, 10 PIs, 7 PSs/PAs/PGs, 9 LPCs, 5 LPEs, 6 ePEs, 4 SMs in hairtail. Salt‐drying had a very different effect on the two fish. Ultimately, the total PLs content decreased slightly (p >.01) in salt‐dried round scad product while increased significantly in hairtail final product (p <.01). Practical applications: The change of PLs caused by salt‐drying is closely related to the flavor and quality of fish products, and is very important for fish preservation and processing. [ABSTRACT FROM AUTHOR]