3.8. Deoxyribose Degradation Assay for •OH-Scavenging

The measurement of •OH radical-scavenging was conducted according to our previously published method [43]. In brief, the sample ethanol solution (4 mg/mL, 9–45 μL) was separately added into tubes. After evaporating the sample solutions in the tubes to dryness, 400 μL of phosphate buffer (0.2 M, pH 7.4) was added to the sample residue. Then, 50 μL deoxyribose (50 mM), 50 μL Na₂EDTA (1 mM), 50 μL FeCl₃ (3.2 mM), and 50 μL H₂O₂ (50 mM) were added. The reaction was initiated by mixing 50 μL ascorbic acid (1.8 mM) and the total volume of the reaction mixture was adjusted to 800 μL with buffer. After incubation at 50 °C for 20 min, the reaction was terminated by addition of 250 μL trichloroacetic acid (10%, w/w). The color was then developed by addition of 150 μL 2-thiobarbituric acid (5%, in 1.25% NaOH aqueous solution) and heated in an oven at 105 °C for 15 min. The mixture was cooled and absorbance was measured at 530 nm (Unico 2100 spectrophotometer, Shanghai, China) against the buffer (as a blank). The hydroxyl radical scavenging activity was calculated based on the formula presented in Section 3.3.