Fractionation, characterization, and gastrointestinal stability of anticancer and antioxidant peptides from sea cucumber (Holothuria scabra) hydrolysates

Sea cucumber hydrolysates with antioxidant and anticancer properties were prepared using papain hydrolysis. The protein hydrolysates were fractionated into peptide groups of >10 kDa (SCPH-I), 3–10 kDa (SCPH-II), 1–3 kDa (SCPH-III), and < 1 kDa (SCPH-IV) using ultrafiltration membranes. The antioxidant and anticancer properties of both crude and fractionated hydrolysates were evaluated. The SCPH-III fraction exhibited the most potent antioxidant properties, with scavenging activities against the 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2′-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), hydrogen peroxide (H 2 O 2 ), and hydroxyl (OH) radicals of 87.96%, 78.48%, 39.39%, and 80.29%, respectively. The antiproliferative effect of the four fractions in the HepG2 cell model showed no significant difference ( p > 0.05). The SCPH-III fraction was selected for peptide characterization using LC-MS/MS with de novo sequencing. Eighteen peptides were identified, among which two peptides demonstrated potent antioxidant and anticancer potential: Thr-Ser-Asp-Gly-Gln-Asn-Tyr-Leu-Leu-Leu-Lys and Phe-His-Val-Asp-Glu-Leu-Lys. The SCPH-III fraction induced significant morphological changes and apoptosis in HepG2 cells, with 87.30% of cells undergoing apoptosis at a 5 mg/mL concentration. Furthermore, the SCPH-III fraction was relatively stable under in vitro gastrointestinal digestion, showing a slight decrease in DPPH and OH radical scavenging activities, whereas the ABTS radical scavenging activity and anticancer activity increased significantly ( p < 0.05). • Papain-produced sea cucumber hydrolysates were separated into four MW-based fractions. • The 1–3 kDa fraction showed the strongest antioxidant and anticancer activity. • The crude and fractioned hydrolysates induced apoptosis and stayed stable after digestion. • Two peptides with potent antioxidant and anticancer activity were characterized.