Development and evaluation of quercetin topical emulgels: Physicochemical and rheological properties, stability and sun protective potential

Quercetin is a lipophilic natural compound that exerts various pharmacological effects such as antioxidant and anti-inflammatory, which are important in preventing skin damage by UV radiation. Emulgels are semisolid dosage forms which consist of a mixture of emulsion and gel, used for delivery of lipophilic substances. The aim of this study was to formulate a UV-protective emulgel of quercetin with proper physical and rheological properties and to examine the influence of excipients on emulgel characteristics. Eight emulgels containing 0.5 % quercetin were prepared with 0.25 % and 0.75 % carbomer 940, 10 % and 20 % castor oil and 1.5 % and 3 % Tween® 20/Span® 20 mixture (1:2). Emulgels were evaluated for their physical appearance, rheology, stability, drug release, occlusivity, and UV-protective effects. The proportion of gelling agent was the predominant factor in determining the rheological properties and the release of quercetin, while the concentration of oil phase had the greatest impact on occlusivity. Emulgels had SPF values ranging from 2.5 to 3.2 and considerable antioxidant activity. The formulation composition significantly affected the characteristics of emulgels, and to a lesser extent the UV-protective activity. Emulgel with 0.75 % gelling agent, 10 % oil phase and 1.5 % emulsifier can be considered as the optimal quercetin emulgel formulation.