Hydroxyl Radical Scavenging Activity Assay

The hydroxyl radical scavenging activity was measured according to the method of Jiang et al. (2019), with slight modifications. Samples of CLPH and its MRPs with different concentrations (0.01, 0.05, 0.1, 0.5, 1, and 2 mg/mL) were prepared in distilled water. Then, 50 μL of each sample was mixed with 50-μL salicylic acid (10 mmol/L, in ethanol), 50-μL ferrous sulfate (1.0 mmol), and 100-μL H₂O₂ (0.5 mol). The mixture was incubated at room temperature for 10 min. The absorbance of the reaction was noted at 510 nm. Hydroxyl radical scavenging activity was calculated using the following formula:

where A₁ is the absorbance of the sample, A₂ is the absorbance of the control (Ferrous sulfate was replaced by distilled water.), and A₃ is the absorbance of the blank (The sample was replaced by distilled water.).