ABSTRACT
A large amount of biologically active compounds, including phenolic acids and flavonoids, are present in the citrus fruits’ peel. If these compounds can be fully extracted from waste citrus peels and utilized, this could not only transform them into value-added byproducts and cut the economic costs, but also reduce the environmental problem of their disposal. Flavonoids, which possess anti-cancer, antimicrobial, antioxidant, and anti-allergic properties, have been extensively applied in the pharmaceutical industry and skincare products. They have also been reported to potentially inhibit coronavirus. In this chapter, the properties of flavonoids will be first discussed. The bioavailability of flavonoids will also be covered. Following this, their potential capacity to inhibit COVID-19 will be illustrated. This chapter offers detailed information from recent studies focused on flavonoids and their extraction and widespread application in the food and pharmaceutical fields. As a starting point for therapeutics against COVID-19, the intake of certain amount of citrus fruits or their extracts could contribute to the prevention of COVID-19. © 2021 by Nova Science Publishers, Inc.