Photostabilization effect of quercetin on the UV filter combination, butyl methoxydibenzoylmethane-octyl methoxycinnamate.

The aim of the study was to investigate the effect of the natural antioxidant quercetin on the photostability of the most widely used combination of UVA (320-400 nm) and UVB (290-320 nm) filters, respectively butyl methoxydibenzoylmethane (BMDBM) and octyl methoxycinnamate (OMC). In order to reproduce the conditions prevalent in commercial sunscreen products, the stabilizing efficacy of quercetin was evaluated in model creams containing BMDBM (3%, wt/wt) together with OMC (4%, wt/wt) and exposed to a solar simulator at an irradiance corresponding to natural sunlight. Quercetin was found to enhance the photostability of the two UV filters in a concentration-dependent way. Addition of quercetin to the sunscreen formulation significantly reduced the photodegradation of BMDBM and OMC from 40.3 +/- 2.4 to 27.7 +/- 2.6% and from 51.3 +/- 2.1 to 42.2 +/- 2.0%, respectively. Moreover, comparative photodegradation studies demonstrated that quercetin was much more effective and at a lower concentration than commonly used stabilizer (octocrylene) and antioxidants (vitamin E, butylated hydroxyanisole). In vitro determination of the UVB and UVA protection parameters showed that the quercetin-based formulation fulfilled the official requirements on sunscreen products. Because of its photostabilizing and multiple antioxidant properties, quercetin represents a useful additive for the formulation of effective broad-spectrum sunscreens containing BMDBM and OMC.