Topical nanocrystals of bioflavonoids: A new technology platform for skin ailments

Bioflavonoids are natural polyphenolic compounds derived from plant metabolites. Broadly, there are eight categories of flavonoids having multiple natural sources and pharmacological actions. Among the wide-ranging spectrum of their pharmacological actions, antioxidant, anti-inflammatory, wound healing, depigmentation, photoprotective and antiaging are beneficial to the skin and show promising actions in treating many skin ailments. However, their lipophilic nature, low solubility and poor skin penetration may cause hindrance in therapeutic actions when given by dermal route and thus, flavonoids have been converted into several nanoformulations. Among other nanotechnology-based platforms, Nanocrystal is studied widely for bioflavonoids to overcome their limitations. Nanocrystals of bioflavonoids are prepared by top-down, bottom-up or combination methods for skin delivery. This review focuses on topical nanocrystals of bioflavonoids, the effect of manufacturing methods on nanocrystal characteristics, in vitro evaluation, and animal studies for different skin ailments. Considering the multiple pharmacological actions of flavonoids, their selective targeting of skin ailments is challenging and newer in vitro models can be used for mechanistic interpretation of their therapeutic benefits. Moreover, based on adequate preclinical data, full-fledged clinical studies should be performed for bioflavonoids nanocrystals which helps in commercial translation.