Antiviral efficacy of hexane extract of Hypericum gaitii Haines against Chikungunya and SARS-CoV-2 viruses: in vitro and in silico approaches.

Ethnopharmacological Relevance: Viral infections have become a public health concern globally. The limited efficacy of existing antivirals against emerging viruses encourages extensive research to find alternative strategies. In this scenario, various plant bioactive compounds have been reported to possess potential against a wide range of illnesses, including viral diseases. Different extracts from the Hypericum genus are known to have anticancer, antioxidant, antimicrobial, antifungal, anti-inflammatory and antiviral properties. Among these, Hypericum gaitii Haines is an endemic and endangered perennial shrub possessing ethnobotanical and medicinal importance. Traditionally, a paste made from the leaves has been used as an ointment for treating skin eruptions. However, the antiviral potency of the same species remains mostly unexplored.

Aim Of The Study: This study aimed to explore the antiviral effect of hexane extract of the leaves of Hypericum gaitii Haines (Code: E38) against Chikungunya virus (CHIKV) and Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) using both in vitro and in silico approaches.

Material And Methods: The antiviral activity of E38 was examined by various techniques like quantitative real-time PCR (qRT-PCR), plaque assay, Western blot, immunofluorescence, and virucidal assay. Liquid chromatography-mass spectrometry (LC-MS) aided in chemical characterization of the extract, while in silico ADMET (Absorption, Distribution, Metabolism, Excretion and Toxicity) analysis, biological target prediction and molecular docking helped to elucidate the possible mechanism of antiviral efficacy.

Results: E38 was found to abrogate CHIKV and SARS-CoV-2 infections efficiently with a drastic reduction of the viral Ribonucleic acids (RNAs), proteins and new viral particle formations (half-maximal inhibitory concentration (IC) of 1.89-4.16 μg/mL in the Vero and C2C12 cells, respectively against CHIKV and 13.86-15.38 μg/mL in Vero and hACE2-A549 cells, respectively against SARS-CoV-2). Further, E38 demonstrated good selectivity indices (SI) (≥52.91 in Vero and >42.06 in C2C12 for anti-CHIKV potential as well as 7.21 and 9.56, respectively in Vero and hACE2-A549 cells against SARS-CoV-2). Notably, the extract interfered in different phases of the CHIKV life cycle, whereas the inhibition was effective in entry and post-entry stages for SARS-CoV-2. Additionally, E38 showed remarkable virucidal activity against both viruses. Further, LC-MS analysis of the extract characterized the presence of 13 main compounds with various biological activities. Amongst these compounds, Mannopine, 2'-Deoxymugineic acid, Avenic acid A and Avenanthramide A were found to have desirable ADMET properties based on in silico analysis. The biological target prediction of these compounds revealed potential to interact with various host proteins like NF-κB p105 subunit, Cathepsin D, Sphingosine kinase 1 (SphK1) and Tripartite motif containing 24 (TRIM24). Moreover, Avenanthramide A demonstrated relatively higher binding affinities for the capsid and nsP2 proteases of CHIKV as well as nsP5 (main protease) and nsP13 (helicase) of SARS-CoV-2 through molecular docking, indicating its direct and/or indirect effects on viral targets and host factors.

Conclusions: The overall study demonstrated that E38 significantly abrogates CHIKV and SARS-CoV-2 infections post-viral entry in vitro, indicating its potential for therapeutic use. Furthermore, this work underscores the effective antiviral potential of the hexane extract of H. gaitii for the first time, encouraging pre-clinical studies towards the development of pan-viral therapeutics.