88 mL potassium persulfate (140 mmol/L) was added to 5 mL ABTS (7 mmol/L), kept in darkness at 25 C for 12e16 h, then diluted with ethanol to an absorbance of 0.70 ± 0.02 at 734 nm. 3.9 mL ABTS cation solution (7 mmol/L) was added to 0.1 mL of extract (prepared as described in Section 2.6, above, and diluted 20 fold with methanol), mixed thoroughly then kept at 25 C for 106 min.