Antiviral potential of bio-oil from Citrus sinensis waste wood as a therapeutic approach against COVID-19

The COVID-19 pandemic has had a significant impact in various areas, particularly in health, and the search for new therapeutic and preventive approaches remains crucial. In this study, we investigated the antiviral potential of bio-oil (BO) obtained from residual woody biomass of Citrus sinensis. BOs were produced through pyrolysis at different heating rates (1, 3, 5, and 7 °C min−1) and subsequently underwent a purification process. Physical-chemical analyses and identification of chemical compounds were performed using Gas Chromatography-Mass Spectrometry (GC/MS). Furthermore, the hemolytic capacity of BOs and their activity against the 3 C L protease enzyme (3CLpro) of SARS-CoV-2 were evaluated. The heating rate was found to affect the chemical properties of the BOs, resulting in variations in pH and chemical composition. A total of 23 chemical compounds were identified, with a significant presence of furans, pyrans, and phenolic compounds. Regarding hemolytic capacity, concentrations equal to or below 1% of BOs showed no hemolytic effect. Concerning antiviral activity, the BO obtained at a heating rate of 5 °C min−1 demonstrated greater efficacy in inhibiting SARS-CoV-2 compared to the BO obtained at a heating rate of 1 °C min−1. This antiviral activity may be associated with the synergistic action of the chemical compounds present in the bio-oils, especially phenolic compounds. These results indicate that the chemical and antiviral properties of BOs can be influenced by the heating rate used during production. In addition, these are unprecedented results and will serve to guide future research aimed at the use of the pyroligneous liquid for the development of a bioactive product.