Ultraviolet (UV) radiation induces DNA damage, oxidative stress, and inflammatory processes in human epidermis, resulting in inflammation, photoaging, and photocarcinogenesis. Adequate protection of skin against the harmful effect of UV irradiation is essential. In recent years naturally occurring herbal compounds such as phenolic acids, flavonoids, and high molecular weight polyphenols have gained considerable attention as beneficial protective agents. The simple phenolic veratric acid (VA, 3,4-dimethoxybenzoic acid) is one of the major benzoic acid derivatives from vegetables and fruits and it also occurs naturally in medicinal mushrooms which have been reported to have anti-inflammatory and anti-oxidant activities. However, it has rarely been applied in skin care. This study, therefore, aimed to explore the possible roles of veratric acid in protection against UVB-induced damage in HaCaT cells. Results showed that veratric acid can attenuate cyclobutane pyrimidine dimers (CPDs) formation, glutathione (GSH) depletion and apoptosis induced by UVB. Furthermore, veratric acid had inhibitory effects on the UVB-induced release of the inflammatory mediators such as IL-6 and prostaglandin-E2. We also confirmed the safety and clinical efficacy of veratric acid on human skin. Overall, results demonstrated significant benefits of veratric acid on the protection of keratinocyte against UVB-induced injuries and suggested its potential use in skin photoprotection.

Lipopolysaccharide (LPS)-induced inflammatory responses in the HaCaT keratinocyte cell line produce proinflammatory cytokines, such as interleukin-1α(IL-1α), tumor neurosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-8 (IL-8) and also increase the expression of inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), and prostaglandins E2 (PGE2). In this study, we developed new natural ingredients for cosmetics that inhibit the pro-inflammatory responses induced by LPS in HaCaT cells. The mixture of Sorbus commixta (SC), Urtica dioica (UD), Phyllostachys nigra (PN), and Rhus semialata gall (RS) extracts blocked the increase of TNF-α IL-1α IL-6, and IL-8. The increase of COX-2, iNOS, and PGE2 were also blocked by it. Finally, the mixture inhibited skin irritation induced by sodium lauryl sulfate (SLS), when applied on skin through IQ chamber Ⓡ . In conclusion, these results show that the mixture of SC, UD, PN, and RS can be used as a primary ingredient to alleviate skin irritation when cosmeceutical products are developed for sensitive skin.