Effects of Flavonoids on Skin according to Their Structural Characteristics: A Review

Functional materials with anti-aging properties that prevent aging in the human body in advance have been attracting attention in the pharmaceutical, food, and cosmetic industries, and active research regarding cosmetic ingredients employing flavonoids among such substances is underway. Therefore, this general review assessed previous studies regarding the effect of various flavonoids on the skin according to their structural characteristics. In this study, the antioxidant, whitening, and antiinflammatory effects of flavonoids present in natural extracts were analyzed. Among the flavonoids, the collagen activity enhancing, antioxidant, anti-inflammatory, and whitening effects of apigenin, baicalein, genistein, naringenin, hesperetin, proanthocyanidins, quercetin, and kaempferol were evaluated. In addition, a study conducted to increase the bioavailability of flavonoids by converting them into clathrates using the structural characteristics of β-cyclodextrin, which further analyzed the difference in the effects of glycoside-containing and non-glycoside flavonoids, was reviewed. Another study reported that the 3'-hydroxyl functional group of flavonoids plays an important role in their antioxidant and anti-inflammatory activities; hence, effects consequent to the modification of their molecular structure were expected. Therefore, the studies that suggest that structural modifications can supplement the efficacy of verified flavonoids are considered to be valid. In future, flavonoids may be used as a stable anti-aging material on the basis of this study on their effects on the skin according to their structural characteristics.