Identification of Chebulinic Acid and Chebulagic Acid as Novel Influenza Viral Neuraminidase Inhibitors

Abstract

The influenza A virus (IAV) causes seasonal epidemics and occasional but devastating pandemics, which are of a major public health concern. Although several antiviral drugs are currently available, there is an urgent need to develop novel antiviral therapies with different mechanisms of action due to emergence of drug resistance. In this study, two related compounds, chebulagic acid (CHLA) and chebulinic acid (CHLI), were identified as novel inhibitors against IAV replication. A reporter virus-based infection assay demonstrated that CHLA and CHLI exhibit no inhibitory effect on IAV entry or RNA replication during the virus replication cycle. Results of viral release inhibition assay and neuraminidase (NA) inhibition assay indicated that CHLA and CHLI exert their inhibitory effect on the NA-mediated viral release. Moreover, oseltamivir-resistance mutation NA/H274Y of NA is susceptible to CHLA or CHLI, suggesting a different mechanism of action for CHLA and CHLI. In summary, CHLA and CHLI are promising new NA inhibitors that may be further developed as novel antivirals against IAVs.

Virtual Screening Identifies Chebulagic Acid as an Inhibitor of the M2(S31N) Viral Ion Channel and Influenza A Virus

“…However, we observed antiviral activities at much higher concentrations (i.e.,~17-34 µM in 50× TCID 50 -based cytopathic assays and notably only~50-61 µM in plaque reduction assays), which may potentially correspond to M2-independent functions. While, the weaker antiviral activity of chebulagic acid is not immediately clear, these differences could reflect our use of assays that measure primary effects of chebulagic acid on viral replication, as opposed to secondary effects of infected culture supernatants reported previously [53]. We also observed similar inhibition of virus strains containing either M2(S31N) or M2(S31), which further supports that chebulagic acid is likely to act on one or more additional viral or host targets independent of M2.…”

“…Interestingly, using a reporter virus with single-cycle infection conditions, the authors also showed no inhibitory effect on influenza A virus entry or RNA replication. Rather, chebulagic acid was observed to block viral release and neuraminidase activity in an enzyme inhibition assay, although the latter activity was observed at 100-fold higher concentrations than what was observed to inhibit viral replication [53].…”

“…More recently, chebulagic acid was reported to inhibit in vitro replication of a panel of influenza A viruses including PR8, as determined by viral yield reduction assays where culture supernatants of infected MDCK cells plus inhibitors were harvested at 24 h post-infection and titered against fresh target MDCK cells [53]. In these assays, the authors observed EC 90 s in the single micromolar range (e.g., 1.26 µM), or comparable to the control inhibitor oseltamivir carboxylate (EC 90 = 3.92 µM), while less activity was observed against influenza B viruses.…”

Drug Development for the Management of Corona Viruses: Insights from Natural Antiviral Agents

“…112,113 The compound has satisfactory activity against several viruses including herpes simplex virus, 114 Human enterovirus 71, 115 HIV, 116 and Influenza. 117 Chebulagic acid inhibits Herpes simplex virus 1 (HSV-1) entry in A549 human lung cells by targeting and inactivating HSV-1 viral particles thus preventing binding, penetration, cell-to-cell spread and secondary infection. The inhibitory action targets at HSV-1 glycoproteins since it blocked polykaryocyte formation mediated by expression of recombinant viral glycoproteins involved in attachment and membrane fusion.…”

“…119 Against influenza A virus, chebulagic acid and chebulinic acid inhibited viral replication through inhibiting neuraminidase-mediated viral release. 117 Basically, this compound's broad antiviral effect is due to its ability to block viral fusion and entry, two important targets in virus life cycle for drug development against coronavirus and/or SARS-CoV-2.…”