Dietary enzyme-treated Hibiscus syriacus L. protects skin against chronic UVB-induced photoaging via enhancement of skin hydration and collagen synthesis

Exposure of skin to UVB radiation is associated with skin thickening, erythema, deep wrinkles, and marked losses of elasticity, resilience, and hydration. To find effective anti-aging materials, scientists have studied not only natural nutritional sources, but also biotransformed metabolites. Although Hibiscus syriacus L., the national flower of Korea has been used extensively throughout history, it has not yet been examined for possible anti aging effects. In this study, skin anti-aging effects of H. syriacus L. water extract (HSL) and enzyme-treated H. syriacus L. extract (ETH) were investigated in normal human dermal fibroblasts (NHDFs) in vitro and in hairless mice in vivo. In UVB-irradiated NHDFs, higher level of type I procollagen and lower levels of matrix metalloproteinase-1 (MMP-1), mitogen-activated protein kinases (MAPKs), and activator protein-1 (AP-1) expression were identified after treatment with HSL and ETH. In photoaged hairless mice, skin thickening and the density of collagen fibers and filaggrin improved after oral administration of HSL and ETH. ETH 1% significantly inhibited melanin content, erythema index (EI), transepidermal water loss (TEWL), stratum corneum (SC) hydration, and wrinkle formation. Palmitic acid and linoleic acid were more abundant in ETH than in HSL. Taken together, both HSL and ETH protect skin from UVB-induced premature photoaging, and enzymatic biotransformed products like ETH have potential for use as valuable functional foods.