Citrus Flavonoids: Biological Activities, Implementation in Skin Health, and Topical Applications: A Review

Citrus fruits are one of the most popular sources of dietary flavonoids, such as hesperidin, hesperetin, naringin, naringenin, quercetin, rutin, diosmin, diosmetin, kaempferol, myricetin, nobiletin, tangeretin, and so on. Flavonoids are polyphenols and aromatic bioactive compounds occurring in plants as secondary metabolites. These participate in various biochemical processes in the human body and help in promoting health. Citrus flavonoids are well-known for their antioxidant and anti-inflammatory properties. They promote wound healing and antimelanoma in addition to free radical scavenging, apoptosis, modulation of lipid metabolism, improvement of insulin sensitivity, and endothelial dysfunction. Citrus flavonoids serve as efficient therapeutics for treating various skin-related issues, such as skin aging/photoaging, skin pigmentation, and maintenance of overall healthy skin. This review is an attempt to compile relevant information from recently published articles addressing the roles of Citrus flavonoids in health-promoting activities, particularly skin health. In addition, it also provides a discussion on the recent progress in developing efficient topical delivery techniques to solve the challenge of flavonoids' poor water solubility and limited permeability into the skin. The review aims to provide a better understanding of the current trends in research and development in Citrus flavonoid biochemistry and their usage in the production of plant-based medicinal and pharma-/nutraceuticals for topical applications.