Effect of oligosaccharyl transglycosylation on the cytotoxicity of cardiac glycoside proscillaridin A and its ability to inhibit hepatitis B virus infection

Abstract

Proscillaridin A, a cardiac glycoside, has been reported to inhibit taurocholic acid uptake via the sodium taurocholate cotransporter polypeptide, a functional receptor for hepatitis B virus (HBV), thereby directly or indirectly inhibiting HBV infection. However, the strong cytotoxicity of proscillaridin A complicates its application as a drug. This study focuses on how the glycan structure of glycosides significantly influences their functions and explores the reduction of cytotoxicity through enzymatic modification of proscillaridin A’s glycan structure. Novel glycosides featuring GN1-type oligosaccharides, derived from sialo- or asialo-N-linked glycans, were synthesized using scillaren A as an acceptor substrate. Scillaren A contains a glucose residue β1,4-linked to the rhamnose residue of proscillaridin A. The synthesis employed Endo-CC-N180H, a mutant of endo-β-N-acetylglucosaminidase. These novel glycosides dramatically reduced cytotoxicity and enhanced cell viability in cultured human hepatocellular carcinoma HepG2 cells. Monitoring of cell death revealed that necrosis by proscillaridin A was suppressed in HepG2 cells treated with the novel glycosides. Furthermore, these novel glycosides maintained an inhibitory potency against HBV infection similar to those of proscillaridin A and scillaren A. These results indicate that the transfer of N-linked glycan-derived oligosaccharides to glycosides may provide a promising platform for endowing them with novel functions for food and pharmaceutical applications.