Quercetin
The most common flavonol in the diet is quercetin.25 Quercetin has
anti-inflammatory and antioxidant effects and act as a
immunomodulator.26 A diet rich in quercetin has been reported to
inhibit the development of carcinogen-induced rat mammary
cancer,27 colonic neoplasia,28 oral carcinogenesis,29 and skin tumor
formation in three models of skin carcinogenesis in mice when
administered by topical application.30 Quercetin may account for the
beneficial effects of dietary fruits and vegetables Table 1] on
mutagens and carcinogens, including metals.31 It is present in
various common fruit and vegetables, beverages, and herbs.32 The
highest concentrations are found in onion.25 Quercetin and rutin
were tested as potential topical sunscreen factors in human beings
and found to provide protection in the UVA and UVB range.33