Bioactive Peptides from Soft-Shelled Turtle: Extraction, Preparation and Biological Activities

Background: Soft-shelled turtle (Pelodiscus sinensis), traditionally used for both medicinal and culinary purposes, is rich in high-quality protein and amino acids, making it an excellent raw material for the preparation of bioactive peptides. In recent years, soft-shelled turtle peptides have gradually become a research focus due to their significant physiological functions, including antioxidant, immunomodulatory, and anti-fatigue activities. Methods: This review systematically sorts out and analyzes 76 relevant research papers published from 2002 to 2026 and comprehensively elaborates on the current state of soft-shelled turtle peptide research, encompassing sources, preparation, and purification strategies, while placing special emphasis on the diverse functional activities and the molecular mechanisms underlying the observed bioactivities. Results: For preparation, enzymatic hydrolysis has become the mainstream method due to its high efficiency and mild conditions; fermentation offers the advantages of low cost and the ability to simultaneously remove odours and enhance flavour, demonstrating good application potential. This review summarizes five key bioactivities, including antioxidant, anti-fatigue, antihypertensive, antitumor, and immunomodulatory effects, and specifically focusing on the current evidence from in vitro and animal studies. Antioxidant and antihypertensive activities have been validated in vivo, whereas the rest remain only tested in vitro, highlighting the need for deeper mechanistic investigation. Conclusions: The review provides an in-depth analysis of the molecular mechanisms through which soft-shelled turtle peptides exert their physiological activities, including free radical scavenging and the regulation of signaling pathways. This review highlights the potential of soft-shelled turtles as a sustainable source of bioactive peptides and offers strategic recommendations for future research.