Oral supplementation of Ilex paraguariensis extract and eggshell membrane exhibit beneficial effects on the skin of mature male rats

Context: Ilex paraguariensis (IP), a South American plant mostly consumed as an infusion, contains several phytocompounds with demonstrated positive effects on skin health and photoprotective properties. Eggshell membrane (ESM), a by-product of the poultry industry, also presents photoprotective properties. Both IP and ESM contain compounds that absorb ultraviolet radiation (UVR) and stop the mechanisms by which UVR damages the skin. The synergistic effects of these natural products on the reparation of skin structure and dermal collagen production deserves to be investigated. Aims: To determine to what extent the oral supplementation of IP and ESM, administrated individually or in combination, promotes beneficial effects on the skin of mature Wistar rats. Methods: The chemical composition of IP and ESM and the spectrophotometric solar protection factor (SPF) of the IP extract were characterized. In vitro, antioxidant and anti-inflammatory effects were assessed using erythrocytes. In vivo investigation consisted of macro and microscopic image analysis and diagnosis of the skin of the dorsal region of rats. Results: The IP extract showed low SPF capacity combined with a protective effect against AAPH-induced erythrocyte haemolysis. IP extract inhibited erythrocyte haemolysis induced by both hypotonic solution and heat. The antioxidant and anti-inflammatory activity of the IP could be explained in terms of its membrane-stabilizing properties. Histologic analysis showed an increase in the collagen content of the skin of supplemented rats. A clear synergistic increase in collagen levels resulted when IP and ESM were administered together. Conclusions: IP and ESM are beneficial for skin health, present synergistic effects, and could be used as ingredients in oral cosmetics.