Although solar exposure is necessary for human health, phototoxicology induced by excessive UVB and UVA radiation, which involves sunburns, skin aging and even tumorigenesis, has been widely researched. Sunscreen is one of the most important ways to protect skin from UV phototoxic damage. As well as inorganic and organic UV filters, some natural products or plant extracts with aromatic rings in their structures, such as flavonoids or polyphenols, can absorb UV to reduce sunburn, acting as a natural UV filter; they also show antioxidant or/and anti‐inflammatory activity. This could explain why, although there are no officially approval natural commercial sun‐filters, more and more commercial sunscreen products containing plant extracts are available on the market. Here we summarize articles focusing on natural UV filters from plant published in the last 6 years, selecting the most significant data in order to better understand the photoprotective activity of natural products and extracts from plants, including their major constituents and main biological effects, methods for evaluating UV radiation resistance, anti‐UV radiation experimental models and anti‐UV radiation mechanisms.

The immunomodulatory effects of R-phycoerythrin (R-PE) from Porphyra haitanensis were investigated by a hydrocortisone (HC)-induced immunosuppressive model in the present research. The results showed that R-PE had immunomodulatory potential, such as increasing spleen and thymus indexes, ameliorating spleen morphology, enhancing the phagocytic capability of macrophages, promoting spleen T lymphocyte proliferation, and strengthening serum hemolysin formation. Furthermore, R-PE elevated the CD4⁺/CD8⁺ ratio and up-regulated the levels of cytokines for Th1, Th2, and Th17 and the mRNA expression of transcription factors T-bet, GATA3, and RORγt. Besides, the levels of cytokines for Treg and transcription factor Foxp3 were down-regulated. The levels of T-bet/GATA3 and RORγt/Foxp3 were increased. R-PE activated the phosphorylation of NF-κB through the TLR4-mediated differentiation pathway. These findings suggested that R-PE exerted immunomodulatory activities in the innate and adaptive immune systems through TLR4/NF-κB mediated CD4⁺ T cell activation and differentiation, which facilitated the further application of R-PE as an immunomodulator.