STABILITY ENHANCEMENT OF L-GLUTATHIONE BY ENTRAPMENT IN WATER-IN-OIL MICROEMULSION

Abstract

L-glutathione (GSH) is one of popular skin-lightening active ingredients since it can reduce the formation of eumelanin or brown-to-black pigment in the skin, resulting in pale color. However, its high hydrophilicity and low stability are hindrances for topical delivery. Thus, development in form of effective formulations such as microemulsion (ME) which can enhance stability and skin penetration of GSH is necessary. This study aimed to increase stability of GSH by incorporation in a water-in-oil (w/o) ME which designated as GSH-ME. GSH-ME was composed of 50% w/w 1:1 Tween80:Span80 as surfactant mixture, 40% w/w palm oil as oil phase, 9.8% w/w 1:1 water:propylene glycol as aqueous phase and 0.2% w/w GSH as the active ingredient. The stability of GSH-ME was evaluated comparing with that of 0.2% w/w GSH aqueous solution after kept in ice box (0±2°C) and at ambient temperature (30±2°C). The chemical analysis was carried out by high performance liquid chromatography (HPLC). The results showed that GSH in aqueous solution was quickly degraded to glutathione disulfide (GSSG) by autoxidation. The changing was found to depend on storage temperature. Degradation of GSH solution when kept at ambient temperature was faster than that when kept in ice box. GSH-ME could retard the degradation rate of GSH to GSSG in comparison with GSH aqueous solution since the oxidation sensitive moiety of GSH was possibly protected in the internal aqueous phase. However, the extended duration of stability of GSH-ME was still not enough for development of a commercial cosmetic product.