Antioxidant Potential of Lycium barbarum Extracts Is Shaped by Extraction Strategy, Not by Total Phenolic Content Alone

The antioxidant potential of plant extracts is frequently evaluated using total phenolic content (TPC), although TPC alone provides limited information about the qualitative composition of phenolic compounds. This study investigated whether extraction conditions influence the antioxidant activity of Lycium barbarum extracts through selective remodeling of their phenolic fingerprint rather than solely through differences in TPC. A total of 160 extraction variants were prepared from conventionally dried and freeze-dried berries using four different solvent systems (water, 70% ethanol, 50% tert-butanol and 50% 1,4-dioxane) at four extraction temperatures (25, 37, 55 and 70 °C) and five extraction times (0.5, 2, 24, 48 and 72 h). Liquid extract recovery, TPC and antioxidant activity were determined using spectrophotometric assays, while selected food-relevant water and ethanol extracts were further characterized by high-performance liquid chromatography with diode-array detection (HPLC-DAD). Extraction conditions markedly affected liquid extract recovery, TPC and antioxidant activity; however, the highest TPC values did not consistently correspond to the strongest antioxidant responses. Correlations between TPC and antioxidant activity were moderate overall and varied with extraction conditions, indicating that TPC alone did not fully explain antioxidant performance. Chromatographic analysis showed that extraction selectively altered the abundance of individual phenolic classes and compounds, generating distinct phenolic fingerprints associated with different antioxidant responses. Together, these findings demonstrate that extraction conditions shape the antioxidant properties of L. barbarum extracts through both quantitative and qualitative changes in the recovered phenolic fraction, providing a basis for selecting extraction conditions and standardizing phenolic-rich ingredients for food and nutraceutical applications.