Assessment of Functional Stability of Photoprotective Formulations Containing Rutin Succinate

The aim of this study was to evaluate physicochemical and functional stability of two different self-emulsified oil/water (O/W) systems. Each system contained 0.4% w/w rutin succinate, which was associated or not with the photo-unstable chemical (7.5% w/w of 2-ethylhexyl 4-methoxycinnamate and 3.0% w/w of 2-hydroxy-4-methoxybenzophenone) or physical filters (3.0% w/w titanium dioxide). A Normal Stability Test was carried out with the formulations containing rutin succinate (S) associated either with sunscreens (MS) or not (M) for 90 days. The formulation systems were assessed for organoleptic, functional, physicochemical and rheological behavior parameters. The MS formulation was found to be homogenous and had no significant alterations of pH, hysteresis area, antiradical activity or Sun Protection Factor values. Such stability was mainly observed when the formulation was incorporated into base cream A. The ability of chemical filters to resist degradation caused by UV radiation in the presence of rutin succinate preventing lipid peroxidation by entrapment of initiator radicals is a mechanism that might explain the results. The combination of rutin succinate to chemical filters improved formulation functionality, as it led to a more stable formulation which maintained the effectiveness of the added sunscreens. Consumer acceptance could be improved, considering that film formation and rheological spreadability characteristics of the tested formulation are better than those of traditional formulations.