Design, synthesis of oleanolic acid-saccharide conjugates using click chemistry methodology and study of their anti-influenza activity

The development of entry inhibitors is an emerging approach to the inhibition of influenza virus. In our previous research, oleanolic acid (OA) was discovered as a mild influenza hemagglutinin (HA) inhibitor. Herein, as a further study, we report the preparation of a series of OA-saccharide conjugates via the CuAAC reaction, and the anti-influenza activity of these compounds was evaluated in vitro. Among them, compound lib, an OA-glucose conjugate, showed a significantly increased anti-influenza activity with an IC50 of 5.47 mu M, and no obvious cytotoxic effect on MDCK cells was observed at 100 mu M. Hemagglutination inhibition assay and docking experiment indicated that lib might interfere with influenza virus infection by acting on HA protein. Broad-spectrum anti-influenza experiments showed lib to be robustly potent against 5 different strains, including influenza A and B viruses, with IC50 values at the low-micromole level. Overall, this finding further extends the utility of OA-saccharide conjugates in anti-influenza virus drug design. (C) 2019 Elsevier Masson SAS. All rights reserved.