Deep eutectic solvent-aided extraction and characterization of collagen from Deccan mahseer (*Tor khudree*) fish scales.

The present study aimed for the extraction and characterization of collagen from Deccan Mahseer (Tor khudree) fish scales using Deep Eutectic Solvents. The fish scales exhibited the protein, moisture, fat, ash and carbohydrate content of 23.66, 52.53, 0.42, 21.56, 1.68% respectively. The highest yield was observed in CC:LA (04.82 ± 01.20), followed by CC:PA (04.62 ± 01.15), and CC: AA (03.07±01.09 %) respectively, indicating that CC:LA DES system is suitable for the extraction of collagen (collagen-LA) from the Deccan Mahseer fish scales. Collage-LA exhibited the 135.08 ± 16.89 mg/g hydroxyproline content and 86.58 % protein content. Further, collagen-LA presented the glycine, proline, alanine, and arginine as prominent amino acids. All collagen samples displayed major protein components, namely α1 (200 kDa), α2 (180 kDa), β (280 kDa), and γ chain (300 kDa, a trimer of the α chain), with slight differences in band intensities. The collagen-LA sample exhibited amide bands A, B, I, II, and III at wavenumbers 3294 cm-1, 2936 cm-1, 1630 cm-1, 1451 cm-1, and 1405 cm-1, respectively. UV spectra of collagen-LA indicated extraction process yielded pure collagen with a purity exceeding 99 %. The collagen-LA demonstrated the highest and lowest protein solubility was noted at pH 2 and pH 5, respectively. NaCl affected the collagen-LA solubility at all concentration. The relative viscosity of collagen–LA exhibited a continuous decline upon heating up to 30 °C. Furthermore, collagen-LA had L* value of 56.31, an a* value of 0.87, and a b* value of 5.75, indicating that the CC:LA collagen was white. Therefore, collagen can be extracted from Deccan Mahseer (Tor khudree) fish scales using Deep Eutectic Solvent which can be used in the food, pharmaceutical, cosmetic, and biomedical applications.