Development and stability evaluation of cosmetic gel formulations containing the glycolic extract of Sapindus saponaria Linnaeus

Abstract

Sapindus saponaria L. is a species widely distributed throughout the Brazilian territory and is recognized for the presence of saponins and phenolic compounds with significant biological and technological potential, which has generated increasing interest in dermocosmetic applications. In this context, the present study aimed to develop and evaluate gel formulations containing different concentrations of S. saponaria glycolic extract, investigating their physicochemical stability, rheological behavior, and antioxidant activity. The leaves of the species were subjected to maceration in 70 % (v/v) ethanolic solution, followed by concentration and standardization of the glycolic extract using propylene glycol. Gel formulations based on hydroxyethylcellulose containing 1 % and 3 % of the extract and a control formulation were developed and subjected to preliminary and accelerated stability studies under different temperature conditions and ultraviolet radiation exposure over a 90-day period. Throughout storage, physicochemical, organoleptic, and rheological parameters were evaluated, as well as antioxidant potential using the DPPH and ABTS assays and total flavonoid content. The formulations exhibited adequate physicochemical and sensory stability when stored under refrigeration and at room temperature, maintaining pH values compatible with topical application, homogeneity, and high viscosity. In contrast, exposure to ultraviolet radiation promoted significant alterations, highlighting the sensitivity of the system to light-induced stress. The formulation containing 1 % of extract stood out by presenting higher antioxidant activity, lower EC₅₀ values, and higher total flavonoid content, indicating that moderate concentrations favor the preservation of biological activity in semisolid systems. It is concluded that S. saponaria represents a promising raw material for the development of antioxidant dermocosmetic gels, provided that appropriate formulation and packaging strategies are adopted, adding scientific, technological, and sustainable value to Brazilian biodiversity.