| Summary: | Abstract Background Syringic acid is a phenolic compound that can be produced through selective hydrolysis of eudesmic acid containing 20% sulfuric acid. The acid is obtained by breaking down components, such as anthocyanin and lignin acid, present in the oils of acai berries and other fruits. Recently, the anti-inflammatory, selective toxicity, anticancer, and antioxidant effects of syringic acid have been studied, but few studies on the effects of syringic acid on human keratinocytes (HaCaT) cells have been published. The present study investigated the antioxidant effects of syringic acid, as a potential cosmetic ingredient, on matrix metalloproteinase (MMP) expression alteration and MMP production control through the activator protein-1 (AP-1) mechanism in HaCaT cells exposed to ultraviolet B radiation. Methods A reactive oxygen species (ROS)-scavenging assay using a luciferase reporter that utilizes the AP-1 response element, an enzyme-linked immunosorbent assay (ELISA), and quantitative reverse transcription polymerase chain reaction (qRT-PCR) were used. To confirm if ROS in HaCaT cells damaged by ultraviolet B are eliminated by syringic acid, 2′-7′-dichlorofluorescein diacetate was used to measure the ROS quantity. qRT-PCR analysis was used to measure the expressions of SOD1 mRNA, GPx1 mRNA, and catalase (CAT) mRNA, which are related to oxidation inhibition. To measure the anti-aging effects of syringic acid, qRT-PCR was used to measure the expression levels of MMP mRNA, c-Jun, and c-Fos. Results ROS were eliminated by syringic acid, and cell aging due to ultraviolet B was suppressed. Results of qRT-PCR analysis confirmed that syringic acid suppressed oxidation in HaCaT cells damaged by ultraviolet B. Further, syringic acid was found to suppress the expression of MMP mRNA, c-Jun, and c-Fos in a concentration-dependent manner. ELISA showed that MMP-1 production decreased in a concentration-dependent manner. The luciferase reporter analysis revealed a concentration-dependent decrease in the transcriptional activity of AP-1 promoter caused by syringic acid. Conclusions Syringic acid was shown to be involved in altering MMP expression and controlling MMP-1 production through the AP-1 mechanism. Thus, the antioxidant and anti-aging effects of syringic acid increased the survival rate of HaCaT cells damaged by ultraviolet B, suggesting that it can be used as a natural phytochemical in cosmetic products.
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