PHOTOPROTECTIVE ACTIVITY OF FLAVONOIDS: A REVIEW

Abstract

In the recent years, there has been a high rise in the magnitude of ultraviolet light reaching the earth surface due to the fact that stratospheric ozone is being depleted at a fast rate, which in turn has led to increased cases of skin cancer and other skin disorders. UVC radiation is extremely detrimental to the skin even in a small amount but fortunately it is absorbed by the molecular oxygen and the ozone layer. UVB radiation makes 4-5% of the UV light and is 1000 times more capable of causing sunburn than UVA. UVA can cause instant tanning effect and chronic exposure to UVA can cause detrimental effects to the underlying structures of the skin and cause premature photo-aging. Flavonoids are natural secondary plant phenolics which are sub-divided into 6 sub-classes. They possess antioxidant and chelating properties. The biochemical activities of flavonoids and their metabolites depend on their chemical structure and the relative orientation of various moieties on the molecule. Natural flavonoids are one of the many candidates as a defence barrier against the UV damage due to their UV absorbing properties, chelating properties, anti-oxidant properties and their ability to modulate several signalling pathways. However these substances must denote their safety in inclusion to its efficacy as a photoprotective agent.