Preparation and identification of antioxidant peptides from Quasipaa spinosa skin through two-step enzymatic hydrolysis and molecular simulation.

Frog skin, a by-product of Quasipaa Spinosa farming, is rich in protein and potentially a valuable raw material for obtaining antioxidant peptides. This study used papain combined with acid protease to digest frog skin in a two-step enzymatic hydrolysis method. Based on a single factor and response surface experiments, experimental conditions were optimized, and the degree of hydrolysis was 30 %. A frog skin hydrolysate (QSPH-Ⅰ-3) was obtained following ultrafiltration and gel filtration chromatography. IC50 for DPPH, ABTS, and hydroxyl radical scavenging capacities were 1.68 ± 0.05, 1.20 ± 0.14 and 1.55 ± 0.11 mg/mL, respectively. Peptide sequences (17) were analyzed and, through molecular docking, peptides with low binding energies for KEAP1 were identified, which might affect the NRF2-KEAP1 pathway. These findings suggest protein hydrolysates and antioxidant peptide derivatives might be used in functional foods.

Aggregation-induced emission luminogens-encoded microspheres preparation and flow-through immunoaffinity chromatographic assay development for microcystin-LR analysis.

Despite decades of efforts, we are faced with the daunting task of on-site ultratrace environmental toxins detecting, especially the microcystins caused by water bloom. In this work, a novel fluorescent microsphere-based flow-through immunoaffinity chromatographic assay has been designed for detecting ultratrace microcystin-LR in water and aquatic products. The aggregation-induced emission luminogens were encapsulated into fluorescent microspheres to ensure microcystin-LR quantitation with a whole analytical time of less than 30 min. Furthermore, the colorimetric images were captured and quantitatively analyzed, which offered a limit of detection at 0.217 pg/mL and a limit of quantitation at 0.362 pg/mL in water and aquatic muscle samples. The developed immunoassays provide average recovery ranging from 79.1 % to 95.7 %, with relative standard deviations less than 13.4 %. Thus, the validated flow-through immunoaffinity chromatographic assay is an easy-to-use alternative for on-site screening of microcystin-LR in water and aquatic samples at picogram levels.