Abstract
Thrombosis triggers various severe diseases, while antithrombotic drugs carry bleeding risks, making the development of novel natural anticoagulants a subject of widespread attention. Poecilobdella manillensis, a prevalent medicinal leech, exhibits remarkable anticoagulant and antithrombotic activities. However, the material basis underlying its anticoagulant effects remains insufficiently investigated. This study aims to mine anticoagulant peptides from P. manillensis by peptidomics analysis, elucidate the material basis of its anticoagulant activity, and provide candidate molecules for developing novel natural anticoagulant drugs. Proteins extracted from P. manillensis were enzymatically digested and fractionated using DEAE-52 and CN columns. The resulting peptide components were analyzed by UPLC-Q-Orbitrap HRMS, and peptide sequences were matched against proteomic databases using Proteome Discoverer. Anticoagulant peptides were predicted using the BIOPEP-UWM database and PeptideRanker server, followed by in vitro and in vivo activity validation. Results showed that the hydrolysate consisted predominantly of low-molecular-weight peptides. 1533 peptides with Mw < 3000 Da (length < 20 amino acids) were identified from the PM-A2 and PM-A3 fractions, accounting for 40.76% of the total. Four peptides selected through predictive screening demonstrated anticoagulant and antithrombotic activities in vitro. Among them, LE-11 significantly prolonged both APTT and TT (P < 0.0001). Furthermore, LE-11 effectively alleviated carrageenan-induced thrombosis in mice, outperforming the heparin control at the mid-concentration (20 mg/kg). In this study, the highly active anticoagulant peptide LE-11 was identified from P. manillensis through peptidomic analysis. These findings establish a solid foundation for developing anticoagulant drugs from this source and provide critical scientific support for its clinical application in treating thrombotic diseases.