ABSTRACT
Objective: To isolate indoleamine 2,3-dioxygenase (IDO) inhibitory constituents from Rabdosia japonica based on bioactivity tracking separation. Methods: The overground part of R. japonica was extracted with boiling water and precipitated by ethanol, the precipitation was collected and lyophilized to obtain XPS, then successively separated by DEAE Sepharose Fast Flow anion-exchange and Superdex-75 gel permeation chromatographic steps to give XPS10-1. A combination of HPGPC, monosaccharide and amino acid composition analysis and IDO inhibitory studies was performed to investigate the structure and bioactivity of XPS10-1. Results: A IDO inhibitory glycoprotein, XPS10-1, was obtained from R. japonica based on activity tracking, its average molecular weight was estimated to 8 852, monosaccharide composition analysis showed the glycosyl part of XPS10-1 was mainly composed of rhamnose and glucose with the ratio of 10.0:2.2, and the protein part was mainly composed of glutamic acid, serine and glycine with mass ratio of 37.3:16.9:45.8. XPS10-1 showed potent IDO inhibitory effect with IC50 of (46.6 ± 3.4) μg/mL, and IC50 of IDO inhibitory effect of XPS10-1 on HeLa cells was (139.0 ± 8.7) μg/mL. Conclusion: In this study, a glycoprotein with IDO inhibitory effect was isolated from R. japonica, which could lay the foundation for the substance basis study of R. japonica.