Background Skin is affected by environmental stress such as ultraviolet exposure. Topically applied antioxidants confer protection against this stress. Spinach thylakoid extracts are plant samples known as photosynthetic membranes containing antioxidant molecules able to dissipate excess of energy and oxidative stress. Methods Antioxidant contents and activities were tested in thylakoid extracts stored for different periods at 4°C to compare their efficacities. Cytotoxicity of thylakoids was tested on human THP‐1 cells along with the capacity to protect from oxidative stress using flow cytometry. Protection of thylakoids against ultraviolet was tested on engineered human skin using two formulations and evaluated by electronic microscopy. Results Results indicate that thylakoid extracts possess antioxidant molecules that were not significantly affected by storage at 4°C whereas photosynthetic activity was storage‐dependent. Thylakoid extracts were not cytotoxic to human THP‐1 cells, and three extracts protected cells against reactive oxygen species. Moreover, formulation comprising 0.1% or 0.01% of thylakoids and sunscreen provided a synergetic protection against UV exposure. Thylakoid extracts mixed with a neutral cream were also able to repair UV damages on engineered human skin. Conclusions Thylakoid extracts contained various antioxidant molecules, and their properties were maintained in over storage at 4°C for more than 72 months. Molecules and enzymes present in thylakoid extracts are involved in protecting and restoring the harmful effects of UV exposure. The involvement of antioxidant molecules such as carotenoids, SOD, and Fe‐S clusters in cellular and regulatory metabolic reactions may explain the observed protective effects.

The anti-inflammatory and antioxidant role of Thykamine, a botanical extract of thylakoides obtained from spinach leaves, has been investigated in animal and cellular models. The oxidative properties have been proven by inhibiting NO production (>98%) in J774A.1 cells and by protecting a linoelic acid emulsion subjected to lipid peroxidation caused by AAPH. Thykamine injected intraperitoneally to rats reduced the inflammatory process of (TNBS)-induced colitis and carrageenan-induced paw edema. As neutrophils are the first cells to migrate to inflammatory sites, the influence of Thykamine on the primary neutrophil functions were studied. Thykamine dose-dependent reduced neutrophil chemiotaxis, phagocytosis, and degranulation. No change in the release of LDH by neutrophils on Thykamine was recorded. Thykamine inhibited by 85% the neutrophil production of O2−. A superoxide recovery activity was observed on a zymography demonstrating a SOD-like enzyme on Thykamine extracts. Spontaneous fluorescence provided by carotenoid and chlorophyll pigments (488/675 nm) detected Thykamine on the surface, in the cytoplasm (mainly central where Golgi are present) and weakly in the nucleus of neutrophils. The results argue that SOD and pigments found in Thykamine are part of its antioxidant and anti-inflammatory properties shown in in vivo and in vitro models of inflammation.