Ethnopharmacological relevance: Long-wave ultraviolet A (UVA) causes skin aging by damaging the fine structures of the skin, such as elastic fibers and collagen fibers, through oxidation. Currently, the use of plant extracts to protect skin from photoaging is a popular method. Panax ginseng C.A. Meyer exerts commendable anti-photoaging and antioxidant effects. P. ginseng Meyer cv. Silvatica, also known as forest ginseng (FG), is a type of ginseng cultivated by artificially simulating the growth environment of wild ginseng aged >15 years. However, there are only a few reports on its anti-photoaging effect on the skin caused by UVA stimulation.
Aim of the study: To investigate whether isolated and extracted FG can inhibit skin photoaging as well as to explore its action mechanism.
Methods: The FG extract (FGE) was obtained from the supernatant of FG after water extraction and alcohol precipitation with the D101 resin. The composition and content of phenolic acids in FGE were determined by high-performance liquid chromatography (HPLC). The MTT assay was performed to detect cell viability. The ratio of SA-β-GAL-positive cells, CoL-I level, 8-OHdG concentration, MDA, GSH, GPx, SOD, and CAT activity were measured using relevant kits. Furthermore, cell cycle alterations and ROS accumulation were assessed by flow cytometry. The expressions of p53, p21, p16, and Keap1 protein were detected by Western blotting. The Nrf2 translocation was monitored by immunofluorescence staining.
Results: The findings revealed that FGE significantly restored UVA injury-induced cell viability, reduced the proportion of SA-β-GAL-positive cells, and increased the level of CoL-I secretion in a dose-dependent manner, where the main ingredients were chlorogenic acid, protocatechuic acid, salicylic acid, p-hydroxybenzoic acid, vanillic acid, ferulic acid, and caffeic acid. Further studies indicated that this phenolic acid mixture (PAM) could alleviate UVA-induced HFF-1 cell cycle arrest and protect the DNA from oxidative damage caused by UVA stimulation. Moreover, the expressions of cell cycle regulatory proteins p53, p21, and p16 and the accumulation of ROS were inhibited, the translocation of Nrf2 into the nucleus was promoted, the expression of Keap1 protein was inhibited, the activity of intracellular antioxidant indicators GSH, GPx, SOD, and CAT was enhanced, and the expression of malondialdehyde (MDA) was inhibited.
Conclusions: Collectively, our results demonstrated that FG phenolic acids protect DNA from oxidative damage by activating Nrf2 to safeguard the skin from photoaging induced by UVA stimulation.
Keywords: Anti-skin photoaging; Forest ginseng; Nrf2; Phenolic acids; UVA.
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