This study evaluated the anti-inflammation and anti-photoaging effects of Camellia sinensis seed flavonoids (CSF) against UVB and UVA irradiation and elucidated the underlying mechanisms. Using UVB-irradiated human keratinocytes and UVA-irradiated human dermal fibroblasts, we found that CSF significantly reduced intracellular ROS and suppressed the secretion of inflammatory factors (PGE-2, TNF-α, IL-6, IL-8) by inhibiting the p38/JNK and NF-κB pathways, along with iNOS and COX-2 expression. In keratinocytes, CSF also downregulated Caspase-3 and upregulated barrier proteins filaggrin and Claudin-1. In fibroblasts, CSF counteracted UVA damage by upregulating collagen IV and XVII at the dermo-epidermal junction and enhancing the production of collagen I, III, and hyaluronic acid in the dermis, mediated via AP-1 inhibition and TGF-β/Smad pathway modulation. These results demonstrate that CSF coordinated anti-inflammatory, barrier-repair, and anti-photoaging actions, highlighting its potential as a promising skincare ingredient.

(1) Background: The pursuit of ingredients that possess both anti-melanogenesis and post-inflammatory hyperpigmentation (PIH) prevention effects has become a new research frontier in cosmetics, though there is little work on plant extract-derived ingredients in this direction. (2) Methods: The study involved evaluating the impact of dark tea extract on melanin content and tyrosinase activity in B16 cells. Meanwhile, Ultraviolet B (UVB)-irradiated assays were conducted on HaCaT cells to assess the secretion of inflammatory factors (IL-1α and IL-1β) and paracrine melanogenic factors (α-MSH, bFGF, and ET-1). Additionally, we performed quantitative real-time polymerase chain reaction (RT-PCR) tests to determine whether the signaling pathways of anti-melanogenesis and PIH punctuation are incorrect. (3) Results: The results showed that dark tea extract significantly inhibited melanin content and tyrosinase activity in B16 cells. In HaCaT cells, the extract reduced the secretion of the aforementioned inflammatory and paracrine melanogenic factors, thereby inhibiting PIH. Moreover, the RT-PCR and the Western Blot results indicated that the dark tea extract could inhibit the melanogenesis signaling pathway of α-MSH/MC1R/MITF and their downstream multiple targets of TYRP-1, TYRP-2, and TYR in B16 cells, while it exerted a PIH inhibition effect by downregulating the p38 MAPK/Nrf2/HO-1 signaling pathway. (4) Conclusions: This study suggests that dark tea extract can not only suppress melanogenesis through multiple targets but also can inhibit UVB-induced PIH, hinting at its skin-brightening efficacy as an agent for the restoration of pigmentation disorders.