Evaluation of the plant glucoside monoterpene indole alkaloid brachycerine for potential protection of human skin against ultraviolet damage

Sunlight ultraviolet radiation A and B (UV-A and UV-B) affect human skin and may be a cause of cancer. Damage to skin nerve fibers and cell DNA is often observed following excessive unprotected exposure. Plants produce numerous specialized metabolites involved in stress mitigation. Brachycerine, a major leaf glucoside alkaloid from the tree Psychotria brachyceras, absorbs in the UV range and is a powerful antioxidant protecting the photosynthetic machinery against this radiation. Herein, the protective effects of new skincare formulations containing brachycerine or foliar extract were tested on ex vivo human skin exposed to UV. Nerve fibers were identified by immunofluorescence, and UV damage or neuroprotection effects were assessed by image analysis. DNA integrity of UV-B treated samples was evaluated by comet assays. UV-A and UV-B significantly reduced (circa 50%) the measured nerve endings density in the untreated or placebo-treated samples. Pre-treatment with tested skincare formulations completely blocked the effects of UV on nerve endings. UV-B-induced DNA damage was abolished by both the alkaloid and the extract. Cytotoxicity assays showed that brachycerine was not toxic to mammalian cells. Formulations with brachycerine or leaf extract effectively protected ex vivo human skin exposed to UV, indicating that these phytochemicals are potential candidate components of new broad spectrum natural sunscreens.