Psoromic Acid, a Lichen-Derived Molecule, Inhibits the Replication of HSV-1 and HSV-2, and Inactivates HSV-1 DNA Polymerase: Shedding Light on Antiherpetic Properties

Molecules. 2019 Aug 11;24(16):2912. doi: 10.3390/molecules24162912.

Abstract

Psoromic acid (PA), a bioactive lichen-derived compound, was investigated for its inhibitory properties against herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2), along with the inhibitory effect on HSV-1 DNA polymerase, which is a key enzyme that plays an essential role in HSV-1 replication cycle. PA was found to notably inhibit HSV-1 replication (50% inhibitory concentration (IC50): 1.9 μM; selectivity index (SI): 163.2) compared with the standard drug acyclovir (ACV) (IC50: 2.6 μM; SI: 119.2). The combination of PA with ACV has led to potent inhibitory activity against HSV-1 replication (IC50: 1.1 µM; SI: 281.8) compared with that of ACV. Moreover, PA displayed equivalent inhibitory action against HSV-2 replication (50% effective concentration (EC50): 2.7 μM; SI: 114.8) compared with that of ACV (EC50: 2.8 μM; SI: 110.7). The inhibition potency of PA in combination with ACV against HSV-2 replication was also detected (EC50: 1.8 µM; SI: 172.2). Further, PA was observed to effectively inhibit HSV-1 DNA polymerase (as a non-nucleoside inhibitor) with respect to dTTP incorporation in a competitive inhibition mode (half maximal inhibitory concentration (IC50): 0.7 μM; inhibition constant (Ki): 0.3 μM) compared with reference drugs aphidicolin (IC50: 0.8 μM; Ki: 0.4 μM) and ACV triphosphate (ACV-TP) (IC50: 0.9 μM; Ki: 0.5 μM). It is noteworthy that the mechanism by which PA-induced anti-HSV-1 activity was related to its inhibitory action against HSV-1 DNA polymerase. Furthermore, the outcomes of in vitro experiments were authenticated using molecular docking analyses, as the molecular interactions of PA with the active sites of HSV-1 DNA polymerase and HSV-2 protease (an essential enzyme required for HSV-2 replication) were revealed. Since this is a first report on the above-mentioned properties, we can conclude that PA might be a future drug for the treatment of HSV infections as well as a promising lead molecule for further anti-HSV drug design.

Keywords: HSV; HSV replication; anti-enzymatic properties; antiherpetic; lichen metabolites; psoromic acid.

MeSH terms

  • Animals
  • Antiviral Agents* / chemistry
  • Antiviral Agents* / pharmacology
  • Benzoxepins* / chemistry
  • Benzoxepins* / pharmacology
  • Carboxylic Acids* / chemistry
  • Carboxylic Acids* / pharmacology
  • Chlorocebus aethiops
  • DNA-Directed DNA Polymerase* / chemistry
  • DNA-Directed DNA Polymerase* / metabolism
  • Herpesvirus 1, Human / physiology*
  • Herpesvirus 2, Human / physiology*
  • Humans
  • Lichens / chemistry*
  • Molecular Docking Simulation*
  • Nucleic Acid Synthesis Inhibitors / chemistry
  • Nucleic Acid Synthesis Inhibitors / pharmacology
  • Vero Cells
  • Viral Proteins* / antagonists & inhibitors
  • Viral Proteins* / chemistry
  • Viral Proteins* / metabolism
  • Virus Replication / drug effects*

Substances

  • Antiviral Agents
  • Benzoxepins
  • Carboxylic Acids
  • Nucleic Acid Synthesis Inhibitors
  • Viral Proteins
  • psoromic acid
  • DNA-Directed DNA Polymerase