Optimization of Extraction Parameters for Cistus incanus Extracts and Evaluation of Their In Vitro Chemical Antioxidant Activity

The extraction conditions of dried Cistus incanus L. herb determine the composition and activity of the resulting extracts and therefore affect their standardization for technological use. This study evaluated the effects of solvent type (methanol, ethanol, acetone, and water), organic solvent concentration (30, 50, 70, and 100%), temperature (20, 40, and 60 °C), and extraction time (3, 6, and 16 h) on process yield, the total content of reducing compounds determined by the Folin–Ciocalteu method and expressed as TPC, and antiradical activity in the DPPH assay. A total of 117 experimental variants were analyzed. Extraction yield ranged from 2.4 to 37.0%, with the highest value obtained by aqueous extraction at 20 °C for 16 h. The extract with the highest yield did not exhibit the highest TPC or DPPH radical-scavenging activity. TPC ranged from 158.7 to 388.8 mg GAE/g lyophilizate, with the maximum obtained using 50% ethanol at 60 °C for 3 h. The highest DPPH radical scavenging activity, 5.11 mmol TE/g lyophilizate, was obtained using 30% ethanol at 40 °C for 3 h. The correlation between TPC and DPPH activity was positive but moderate, indicating that the Folin–Ciocalteu reactive fraction explained only part of the variation in antiradical activity. The integrated utility index ranked 30% ethanol at 40 °C for 3 h highest among the experimentally evaluated conditions. These findings provide a basis for further chemical characterization and process development of C. incanus extracts.