Background: Sunscreens and catechins from grape seed extract (GSE) are sensitive to various environmental factors and undergo certain changes over time that might affect the effectiveness of the final product. To this date, effects of thermal storage conditions have not been sufficiently addressed to guarantee the long-term stability of sunscreen formulations.
Aims: To study the chemical and mechanical accelerated and long-term stability of sunscreen formulation containing GSE at the Climatic Zone IVb conditions.
Methods: Stability studies were performed for 6 months for accelerated stability study at 30°C ± 2 and 50°C ± 2, 75 ± 5% relative humidity; and long-term stability study at 5°C ± 5. The quantification of constituents of three formulations: sunscreen with GSE, cream with UV filters only, and cream with GSE only was performed by high-performance liquid chromatography. In vitro spectrophotometry was used to determine changes in sun protection effectiveness through SPF and UVAPF values. Mechanical stability was evaluated by textural and rheological analyzes.
Results: All tested formulations were less stable at high-temperature conditions. The contents of catechin (С) and epicatechin (EC) in sunscreen with GSE were reduced to 37% and 50% at 50°C, respectively, whereas UV filters appeared to be stable. However, despite the significant reduction in catechins over time, polyphenols in GSE remained unchanged at different stored conditions. The SPF values and water resistance of sunscreen with GSE were maintained throughout the study.
Conclusions: A current in vitro study has shown that sunscreen with GSE is a value-added anti-aging ingredient in sunscreen formulation because its polyphenolic composition as well as SPF values and water resistance were maintained under all temperature conditions over time.
Keywords: SPF; chemical stability; grape seed extract; sunscreen; water resistance.
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