Antioxidant activity of citrus limonoids and investigation of their virucidal potential against SARS-CoV-2 in cellular models

The COVID-19 pandemic represents an unprecedented global emergency. Despite all efforts, COVID-19 remains a threat to public health, due to the complexity of mass vaccination programs, the lack of effective drugs, and the emergence of new variants. A link has recently been found between the risk of developing a severe COVID-19 infection and a high level of oxidative stress. In this context, we have focused our attention on natural compounds with the aim of finding molecules capable of acting through a dual virucidal–antioxidant mechanism. In particular, we studied the potential of grapefruit seed extracts (GSE) and their main components, belonging to the class of limonoids. Using chemical and biological approaches including isolation and purification of GSE, antioxidant and virucidal assays, we have shown that grapefruit seed constituents, belonging to the class of limonoids, are endowed with remarkable virucidal, antioxidant and mitoprotective activity.