Suppressive effects of ethanol extract of Aralia elata on UVB-induced oxidative stress in human keratinocytes / 한국영양학회지

ABSTRACT

PURPOSE: Ultraviolet (UV)-induced oxidative stress contributes to several adverse biological effects on skin. Many phenolic phytochemicals have been shown to have antioxidant properties and protect skin cells from UV-induced oxidative damage. In this study, we investigated whether or not Aralia elata (AE) has a protective effect against UVB-induced reactive oxygen species (ROS), ultimately leading to photoaging. METHODS: Phenolic content of dried AE and antioxidant properties of AE extract in 70% ethanol weredetermined by measuring DPPH and ABTS radical scavenging activities and ferric reducing antioxidant power (FRAP). The effect of AE extract on cellular ROS generation and expression levels of oxidative stress-response proteins such as superoxide dismutase (SOD)-1, catalase, nuclear factor-erythroid 2-related factor (Nrf)-2,and heme oxygenase (HO)-1 in UVB-irradiated (75 mJ/cm²) human keratinocytes (HaCaT) were further determined by 2'-7'-dichlorofluoresceine diacetate assay and Western blotting, respectively. RESULTS: The total phenolic and flavonoid contents of dried AE were 20.15 mg tannic acid/g and 18.75 mg rutin/g, respectively. The IC₅₀ of AE extract against DPPH radical was 98.5 µg/mL, and ABTS radical scavenging activity and FRAP upon treatment with 1,000 µg/mL of AE extract were 41.8 µg ascorbic acid (AA) eq./mL and 29.7 µg AA eq./mL,m respectively. Pretreatment with AE extract significantly reduced (p < 0.05) ROS generation compared to that in UVB-irradiated control HaCaT cells. Pretreatment with AE extract reversed reduction of Nrf-2 and SOD-1 protein expression and induction of HO-1 protein expression caused by UVB exposure in HaCaT cells, whereas it did not affect catalase expression. CONCLUSION: AE extract in 70% ethanol demonstrated a protective effect against UVB-induced oxidative stress and decreased expression of Nrf-2 and SOD-1 in human keratinocytes. These findings suggest that AE ethanol extract might have potential as a natural resource for a skin antiphotoaging product in the food and cosmetic industry.