Protective effects of citrus and rosemary extracts on UV-induced damage in skin cell model and human volunteers

• UV radiation is the major cause of skin disorders such as photoaging and melanoma.
• Oral consumption of photoprotective plant compounds may contribute to skin health.
• Citrus and rosemary compounds protect synergistically skin cells from UV radiation.
• Oral ingestion of the combination reduces MED upon UV radiation in human volunteers.

Ultraviolet radiation absorbed by the epidermis is the major cause of various cutaneous disorders, including photoaging and skin cancers. Although topical sunscreens may offer proper skin protection, dietary plant compounds may significantly contribute to lifelong protection of skin health, especially when unconsciously sun UV exposed. A combination of rosemary and citrus bioflavonoids extracts was used to inhibit UV harmful effects on human HaCaT keratinocytes and in human volunteers after oral intake. Survival of HaCaT cells after UVB radiation was higher in treatments using the combination of extracts than in those performed with individual extracts, indicating potential synergic effects. The combination of extracts also decreased UVB-induced intracellular radical oxygen species (ROS) and prevented DNA damage in HaCaT cells by comet assay and decreased chromosomal aberrations in X-irradiated human lymphocytes. The oral daily consumption of 250 mg of the combination by human volunteers revealed a significant minimal erythema dose (MED) increase after eight weeks (34%, p < 0.05). Stronger protection was achieved after 12 weeks (56%, p < 0.01). The combination of citrus flavonoids and rosemary polyphenols and diterpenes may be considered as an ingredient for oral photoprotection. Their mechanism of action may deserve further attention.

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