Assessment of the Antioxidant Activity of Lyophilized Cistus creticus Extract as a Functional Fortifier in Yogurt: A Cellular and Non-Cellular Evaluation

Experimental evidence indicates that aqueous extracts of the Cistus genus have significant antioxidant properties, suggesting their potential as food fortifiers. In the present study, the antioxidant capacity and total phenolic content of lyophilized Cistus creticus extract were examined before and after in vitro digestion. Three concentrations of Cistus creticus extract were evaluated before and after in vitro gastrointestinal digestion, along with yogurt products fortified with these extracts, examined after digestion. Biochemical and cellular analyses were performed to assess these properties. The results showed statistically significant differences in total antioxidant capacity and total phenolic content, with values increasing from the lowest to the highest concentration studied, for both the lyophilized extracts and fortified yogurts after digestion. Additionally, cellular antioxidant activity after digestion was concentration-dependent (p < 0.05) within the range 25–500 mg/mL for both the extracts and fortified yogurts. In conclusion, based on the high phenolic content and the increased antioxidant capacity observed in epithelial cells, 250 mg of extract per 200 g of yogurt was proposed as the optimal fortification dose.