Extraction, characterization and antioxidant activity evaluation of collagen from Monopterus albus bones

Abstract BACKGROUND Monopterus albus bones are a rich source of collagen, yet they are often discarded as processing byproducts, leading to resource waste. This study aimed to establish an efficient ultrasound‐assisted enzymatic extraction method for collagen from M. albus bones, characterize its structural properties, and evaluate its in vitro antioxidant activity. RESULTS The optimal extraction conditions were determined via single‐factor experiments and Box–Behnken response surface methodology as follows: solid–liquid ratio of 1:20 g g −1 , pepsin addition of 20 g kg −1 , enzymatic hydrolysis time of 2 h, ultrasonic time of 22 min, ultrasonic power of 375 W, and ultrasonic frequency of 40 kHz. Under these conditions, the collagen extraction yield reached 35.00 ± 0.48%. The extracted product was identified as type I collagen by ultraviolet spectroscopy and sodium dodecylsulfate–polyacrylamide gel electrophoresis. Scanning electron microscopy revealed a loose, porous fibrous network structure, while X‐ray diffraction indicated a combination of disordered flexibility and ordered active conformation. Differential scanning calorimetry and thermogravimetric analysis showed a thermal denaturation temperature of 92.70 ± 1.24 °C and good stability below 200 °C. In vitro antioxidant assays demonstrated that the collagen exhibited strong free radical scavenging activity, with IC 50 values of 6.01 ± 0.36 mg mL −1 against DPPH radicals, 7.63 ± 0.24 mg mL −1 against superoxide anion radicals, and 17.71 ± 0.19 mg mL −1 against hydroxyl radicals. CONCLUSION This study provides a practical and sustainable ultrasound‐assisted enzymatic extraction method for obtaining high‐quality type I collagen from M. albus bones, which demonstrates excellent thermal stability and potent antioxidant activity. These findings support the high‐value utilization of M. albus processing byproducts and lay a foundation for the industrial development of natural antioxidant collagen. © 2026 Society of Chemical Industry.