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

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.

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 IC₅₀ 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.

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.