Ellagitannins From Pomegranate Flower With Whitening and Anti-Skin Photoaging Effect

A new depside glucoside rosarugoside E (1), together with four known compounds punicalagin (2), corilagin (3), granatin B (4), and ellagic acid (5) were isolated from the ethanol extract of pomegranate (Punica granatum L.) flower. Their structures were identified based on careful analysis of various spectral data including ultraviolet, infrared, high-resolution electrospray ionization-mass spectrometry, and 1D and 2D nuclear magnetic resonance. The whitening and anti-aging effects of all compounds were evaluated based on the levels of protein and gene. The result displayed that all compounds exhibited inhibitory activity for tyrosinase at maximum safe concentration, except for compound 2. Compounds 3 and 5 exhibited significant inhibitory activity for tyrosinase, indicating their whitening efficacy. The anti-aging activity evaluation assay showed that all compounds could downregulate the expression of the MMP1 gene, decrease the expression of matrix metalloproteinase 1, and increase the content of type 1 collagen at the maximum safe concentration compared with negative control (ultraviolet A irradiation treatment).