Evidence of Synergistic Activity of Medicinal Plant Extracts against Neuraminidase Inhibitor Resistant Strains of Influenza Viruses

Abstract

The frequent emergence of drug resistant influenza viral strains emphasizes the urgent and continual need to develop new antiviral drugs. Given the encouraging findings of previous studies on antiviral compounds from plant sources, this study focused on medicinal plants from Borneo that were traditionally used to treat symptoms of influenza infection. Following the promising results of earlier investigations, four plant extracts that demonstrated multiple modes of viral inhibition were studied against wild-type and neuraminidase (NA) inhibitor-resistant strains of Types A and B influenza viruses. The extracts exhibited more pronounced activities against the wild-type viruses than the NA inhibitor-resistant strains. Variations in the antiviral potential of the extracts collected from different parts of the same plant were also evidenced in the in vitro micro-inhibition assays. Even though all plant extracts affected NA activity of all viruses, only two extracts demonstrated hemagglutination inhibitory (HI) activities against Type A pandemic H1N1 and Type B viruses. Furthermore, Receptor Destroying Enzyme (RDE) treatments of extracts exhibiting HI activities indicated the presence of sialic acid (SA)-like component(s) that may be responsible for HI activity. Since the antiviral potential of extracts was not completely suppressed by RDE, the possibility of non SA-like antiviral components cannot be ruled out. Therefore, synergistic activity between SA-like and non SA-like components contained in the plant extracts may be responsible for the demonstrated antiviral potential. The results also indicated the presence of non SA-like components that may act against other viral proteins apart from hemagglutinin (HA) and NA.

In vitro evaluation of novel antiviral activities of 60 medicinal plants extracts against hepatitis B virus

“…Furthermore, the highest anti-HBV activity of C. grandis and C. epigeus was associated with the crude ethanolic-extract, indicating the possibility of synergy among the antiviral phytochemical constituents of the extract. Synergistic activity of antiviral components of plant extracts that act by different mechanisms has been reported previously (33). Traditionally, crude extracts of C. grandis are used to treat coughing, bronchitis, skin diseases, tongue sores and liver disorders (34).…”

A Comprehensive Review on Medicinal Plants as Antimicrobial Therapeutics: Potential Avenues of Biocompatible Drug Discovery

“…The anti-diarrheal activity of extracts collected from the guava leaf is one such example. The extract of guava leaf is not bactericidal, but affects crucial pathogenic events of colonization and toxin production by diarrheal pathogens [66]. The study by Rajasekaran et al [67] also demonstrates that the presence of multiple antiviral components in plant extracts interfaces with different viral proteins at various stages of viral replication.…”

Towards Advances in Medicinal Plant Antimicrobial Activity: A Review Study on Challenges and Future Perspectives

“…Moreover, they have the ability to interfere with intermediary metabolism [ 85 ], to induce the coagulation of cytoplasmic constituents [ 86 ] and disrupt or inhibit the formation of biofilms, which confer a protective advantage to pathogens during infection [ 87 , 88 ]. The presence of multiple antiviral components in medicinal plant extracts interfaces with different viral proteins at various stages of viral replication [ 89 ].…”