Photoprotective properties of combined extracts from Diospyros lotus leaves and Curcuma longa rhizomes against chronic UVB‐induced photodamage

The synergistic effects of combined ethanolic extracts of Diospyros lotus leaves (DLE) and Curcuma longa rhizomes (CLE) were investigated for their protective effects on chronic Ultraviolet-B (UVB)-induced skin photodamage in SHK-1 mice. The degree of protection was measured by using biochemical parameters such as malondialdehyde, reduced glutathione, superoxide dismutase, catalase, Akt activation, and nuclear factor (erythroid-derived 2)-like 2 (Nrf2) activities, collagen degradation among others. DLE, CLE, and DLE/CLE demonstrated significant photodamage protection by upregulating endogenous antioxidant in mice skin through the activation of Akt and Nrf2 activities; prevented epidermal hyperplasia; mast cell infiltration into the skin and collagen degradation. The effects of the combined extract were greater than the effects of the single extracts. Also, the synergistic effects of DLE/CLE were comparable to that of standard drug, ascorbic acid. This study suggests the synergistic protective role of DLE/CLE in the treatment UVB-induced photodamage. Practical application The use of synthetic antioxidant products to prevent oxidative-related stress, especially from UV radiations is frequently accompanied with severe side effects. Therefore, the search for natural antioxidants is of utmost importance. Polyphenols are of great interest due to their antioxidant properties and small molecular weight that permits them to penetrate the skin. Diospyros lotus (rich in myricitrin) and Curcuma longa rhizomes (rich in curcumin) are both edible plants. This research investigates the synergetic effects of extracts of both plants against chronic UVB-induced oxidative stress. Data obtained from this study shed light on using plant-based products both alone and in synergy as potential functional foods and nutraceuticals for the prevention of UVB-induced oxidative stress. The results of this research could serve as a base for further research on these extracts as a source of antioxidant and promotes the usage of these plants on a large scale as functional food materials.