Haiwei Li, Shouxin Wang, Lihe Zhang, Renyang Xu, Man Li, Yongmin Zhang, Sulong Xiao, Demin Zhou, Central South University, Chinese Academy of Sciences [Changchun Branch] (CAS), State Key Laboratory of Natural and Biomimetic Drugs, Peking University [Beijing], Institut Parisien de Chimie Moléculaire (IPCM), Chimie Moléculaire de Paris Centre (FR 2769), Institut de Chimie du CNRS (INC)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Centre National de la Recherche Scientifique (CNRS)-Ecole Nationale Supérieure de Chimie de Paris - Chimie ParisTech-PSL (ENSCP), Université Paris sciences et lettres (PSL)-Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris (ESPCI Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Institut de Chimie du CNRS (INC)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS), Glycochimie Organique Biologique et Supramoléculaire (GOBS), Université Paris sciences et lettres (PSL)-Université Pierre et Marie Curie - Paris 6 (UPMC)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Chimie Moléculaire de Paris Centre (FR 2769), Key Laboratory of Resource Biology and Biotechnology, and Northwest University, Xi'an
It is urgently necessary to develop more effective anti-influenza agents due to the continuous emergence of drug-resistant strains of influenza virus. Our earlier studies have identified that certain pentacyclic triterpene derivatives are effective inhibitors of influenza virus infection. In the present study, a series of C-28 modified pentacyclic triterpene derivatives via conjugation with a series of polyphenols were synthesized, and their antiviral activities against influenza A/WSN/33 (H1N1) virus in MDCK (Madin-Darby canine kidney) cells were evaluated. Four compounds 23m, 23o, 23q and 23s displayed robust anti-influenza potency with averaged IC50 values at the low-micromole level, surpassing the potency of oseltamivir. In addition, the in vitro cytotoxic activity of the four conjugates against MDCK cells showed no toxicity at 100 μM. Further mechanism studies of compound 23s, one of the best representative conjugates with IC50 value of 5.80 μM and a selective index (SI) value of over 17.2, by hemagglutination inhibition (HI), surface plasmon resonance and molecular modeling indicated that this conjugate bound tightly to the viral envelope hemagglutinin (KD = 15.6 μM), thus blocking the invasion of influenza viruses into host cells.