Methoxy-Monobenzoylmethane Protects Human Skin against UV-Induced Damage by Conversion to Avobenzone and Radical Scavenging

Abstract

Avobenzone, one of the most commonly used UV filters in topical sunscreens, is susceptible to photodegradation with a consequential reduction of its UV absorbing properties. This loss of function may lead to skin irritation, photodermatosis, and photoallergic reactions caused by photodegradation byproducts. In this work, we aim to address this issue with a substance named methoxy-monobenzoylmethane (MeO-MBM), which is neither a UVB nor a UVA filter, but which converts to avobenzone, a known and approved UVA filter, under mainly UVB light irradiation. The antioxidant and intracellular radical formation properties of MeO-MBM were compared to the ones of avobenzone. The UV irradiation of MeO-MBM led to an increase in UV absorption primarily in the UVA range after conversion, both in vitro and in vivo. HPTLC and UHPLC studies illustrate the conversion of MeO-MBM to avobenzone in vitro after irradiation at 250 kJ/m2, reaching a conversion rate of 48.8%. A stable molecular antioxidant activity was observed, since 100-µM MeO-MBM was measured to be 11.2% in the DPPH assay, with a decrease to 9.7% after irradiation. In comparison, the molecular antioxidant activity of 100-µM avobenzone was determined to be 0.8%. In keratinocytes, MeO-MBM reduces the intracellular ROS by 90% and avobenzone by 75% with tBHP as the inducer and by 53% and 57%, respectively, when induced by pyocyanin, indicating the redox scavenging capacity of both these molecules. These results indicate that MeO-MBM functions initially as an antioxidant material and as a photoantioxidant during its conversion process to avobenzone. This research provides insight into the development of active ingredients for topical applications with dynamic functionalities. Using this approach, we demonstrate the possibility to extend the UV protection offered to skin cells while combating cellular stress in parallel.

Methoxy-Monobenzoylmethane Protects Skin from UV-Induced Damages in a Randomized, Placebo Controlled, Double-Blinded Human In Vivo Study and Prevents Signs of Inflammation While Improving the Skin Barrier

“…To protect skin and reduce the signs of inflammation, improving and strengthening the skin barrier are beneficial and work in concert as effective UV-related anti-aging ingredients. Interestingly, MeO-MBM acts as a conversion material and thus reduces UV irradiation-induced physical damage, but when exposed to living cell layers of skin, it is a potent ingredient to modulate signal transduction and reduces ROS and RNS generation [ 4 ]. Typically for a conversion material the release of hydrogen and the following reaction with UV-induced radicals come first to mind as the key functionality of MeO-MBM as it releases two hydrogens via the conversion to avobenzone.…”

“…Classical antioxidative materials are used to support cells to neutralize radicals before damaging the cells or macromolecules associated with loss of function such as lipid peroxidation. MeO-MBM exhibits dose-dependent antioxidative properties with and without irradiation which are in contrast to avobenzone, where no DPPH reduction was measured [ 4 ].…”

“…In summary, MeO-MBM is a potent molecule in sun care formulations capable of maintaining the SPF by converting to avobenzone and releasing two hydrogen radicals that reduce the overall production of reactive radical species, thus improving the health status of cells and skin [ 4 ]. By that reduced radical formation, the onset of inflammatory reactions which accelerate the chronic age-related inflammation processes called inflammaging is decreased.…”

“…Given that UV filters require regulatory approval by the Food and Drug Administration (FDA), it is desirable to add sun filter boosting materials or conversion materials to maintain the sun protection factor (SPF) in case of UV-induced degradation of the key sun filter material in sun care formulations [ 3 ]. Methoxy-monobenzoylmethane (MeO-MBM) belongs to the second class of materials as it has been shown that it converts into 4-tert-butyl-4′-methoxydibenzoylmethane (avobenzone) in vitro and in vivo after having been exposed to UV irradiation [ 4 ].…”

“…The conversion of MeO-MBM results in the formation of two intermediate hydrogen radicals, which can directly neutralize radicals formed during the degradation of avobenzone or further react with radical species present in UV-exposed human skin protecting the skin against UV stress. This is referred to as photoantioxidative functionality [ 4 ].…”