In Vitro Antiviral Activity of the Fungal Metabolite 6-Pentyl-α-Pyrone Against Bovine Coronavirus: A Translational Study to SARS-CoV-2

Abstract

The recent COVID-19 pandemic has prompted the scientific community to prioritize the discovery of preventive methods and new therapeutics, including the investigation of natural compounds with antiviral potential. Fungal secondary metabolites (SMs) represent a promising source of antiviral drugs due to their structural diversity and intrinsic biocompatibility. Herein, the antiviral activity of 6-pentyl-α-pyrone (6PP) against bovine coronavirus (BCoV) has been evaluated in vitro. Considering that BCoV and SARS-CoV-2 are both members of the Betacoronavirus genus and share several key features, BCoV represents a valuable reference model for human coronavirus research. A non-cytotoxic dose of 6PP was used on MDBK cells to evaluate its antiviral activity against BCoV. Different experimental conditions were employed to examine cell monolayer protection both pre- and post-infection, as well as the potential inhibition of viral internalization. Overall, post-infection 6PP treatment reduced viral load and decreased viral internalization. Results were analyzed using viral titration and quantitative PCR, while data interpretation was performed by statistical software tools. This study presents a novel fluorescence quantification approach with high confidence demonstrated by its significant concordance with RT-qPCR results. These data suggest that 6PP could be an effective antiviral agent for BCoV, warranting further investigation of its role in coronavirus inhibition.

Keywords: 6-pentyl-α-pyrone; BCoV; COVID-19; antiviral activity.

Figure 1

Dose–response curve for 6PP generated using GraphPad Prism 10.3.1 program, Intuitive Software for Science, San Diego, CA, USA. The x-axis represents the concentration of the compound (µg/mL), while the y-axis shows the percentage of cell mortality (%). The curve was fitted using a nonlinear regression analysis. Results were validated in Python Programming Language 3.9.18, with calculations of R² (coefficient of determination), SD (Standard Deviation), and SE (Standard Error). R² indicates the proportion of observed variance in the independent variable that is explained by the independent variables within the regression model.

Figure 2

Positive immunofluorescence obtained for both the virus–compound (VC) mixture group and the control virus (CV) mixture group at different time intervals and room temperature (RT).

Figure 3

Correlation analysis between virus–compound (vc_values)/control virus values (cv_values) and the various temperatures (Tp) and dilutions (Dil).

Figure 4

Fluorescence (a) and cDNA viral copies (b) quantification detected in the different antiviral protocols. AU = Arbitrary intensity Units, Protocol A-1: Treatment of cell monolayer with 6PP for 72 h, Protocol A-2: Treatment of cell monolayer with 6PP for 3 h, Protocol B-1: Treatment with 6PP at 4 °C, Protocol B-2: Treatment with 6PP at 37 °C, Protocol C: Viral internalization inhibition.