| Summary: | Ultraviolet (UV) radiation harms the skin, causing oxidative damage, inflammation, and disruption of the skin’s barrier function. There is considerable interest in identifying new natural ingredients with antioxidant and anti-inflammatory properties to serve as adjuvants in sunscreens. The flavonoid morin (<b>1</b>) can undergo structural modifications to enhance its biological properties. The aim of this study was to synthesize two new morin-Schiff base derivatives, morin oxime (<b>2</b>) and morin semicarbazone (<b>3</b>), comparing their photoprotective effects with that of the parent compound on UVB-exposed HaCaT keratinocytes. The chemical structure of the novel compounds was revealed based on spectroscopic data analysis. Our findings demonstrated that derivatives <b>2</b> and <b>3</b> enhanced the light absorption capability in the UV–visible (vis) range compared to <b>1</b>. Tested compounds exhibited a higher scavenger capacity than Trolox. Moreover, pre-treatment with all compounds protected HaCaT cells from UVB-induced cell death. Compound <b>3</b> demonstrated the strongest antioxidant effect, reducing reactive oxygen species (ROS) generation and, subsequently, malondialdehyde (MDA) levels. Additionally, compounds <b>2</b> and <b>3</b> exhibited greater anti-inflammatory effects than compound <b>1</b>, significantly reducing interleukin (IL)-6 production levels at all tested concentrations. These findings have demonstrated, for the first time, a promising photoprotective activity of two new Schiff base derivatives and suggest their use as natural sunscreen ingredients.
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