2.6. Screening of Antioxidants from the Extract Using Offline DPPH-HPLC

The offline DPPH-HPLC strategy was used to screen the potential antioxidants in the extract before separation. Briefly, 150 µL of DPPH solution (2.5 mg/mL in MeOH) and 50 µL of the extract solution (10 mg/mL in MeOH) were mixed and incubated for 30 min at 37 °C. Thereafter, the reaction solution (injection volume 10 µL) was subjected to HPLC assay. MeOH was used to replace the DPPH solution for incubation with the sample to be used as a DPPH-free control group. The compounds with reduced HPLC peak areas from DPPH group compared with those from the DPPH-free group were assigned as potential antioxidants.