Species of the Citrus genus are known as rich sources of phenolic compounds. Peels of Citrus tachibana and Citrus unshiu are used in herbal formulations, sometimes in similar ways. In this study, we examined the effects of plant maturity and genetic background on the total phenolic contents and quantities of specific flavonoids in C. tachibana peel. In addition, we compared these values in C. tachibana and C. unshiu peels. The total phenolic contents and the contents of nobiletin, tangeretin, and hesperidin were higher in the extracts of the immature peel than in those of the mature peels of C. tachibana; moreover, the quantities of these compounds were also influenced by the genetic background of C. tachibana. In the extracts of C. unshiu peel, the contents of total phenolics, nobiletin, and tangeretin were lower than those of C. tachibana peel. However, the hesperidin content was higher in extracts of C. unshiu peel than those of C. tachibana peel. This study evaluated the phenolic and flavonoid contents of C. tachibana and C. unshiu in an effort to provide new insights into herbal medicines for further study and utilization.

The Chaenomeles sinensis fruit is used as an effective antitussive agent, analgesic, and diuretic in traditional Chinese medicine. It has been reported that C. sinensis fruit extracts have antimicrobial and anti-inflammatory effects. However, there are very few reports about the effects of C. sinensis extracts on skin. In this study, we investigated the effect of C. sinensis extracts on skin aging. The results of in vitro assays showed that whole fruit extracts of C. sinensis had superoxide dismutase (SOD)-like activity and inhibited the activity of dermal extracellular matrix proteases: Elastase and collagenase. The inhibitory effect of the whole fruit (containing seeds) extract on elastase activity was higher than that of the sarcocarp (seeds removed) extract. Further, the sarcocarp extract showed a higher level of SOD-like activity and a greater inhibitory effect on collagenase activity than the whole fruit extract. In particular, among the three activities studied, the sarcocarp extract showed the most significant inhibitory effect on collagenase activity at low concentrations. The polyphenol-rich fraction obtained from the sarcocarp showed significant collagenase inhibition. Based on these results, we concluded that phenolic compounds from C. sinensis sarcocarp have the potential to protect against skin aging through anti-collagenase activity.