Figure 2.

Results of penetration study: (a) Penetration of apple extract into skin layers after application for 24 h; (b) Penetration of chlorogenic acid, rutin, quercetin, (+)-catechin, and (−)-epicatechin standard solutions into skin layers after application for 24 h. Uppercase letters indicate a statistically significant difference in the amount of phenolic compounds that penetrated into the epidermis layer; lowercase letters indicate a statistically significant difference in the amount of phenolic compounds that penetrated into the dermis layer (p < 0.05).