ABTS solution, CuCl 2 , neocuproine, NH 4 Ac, acetone, diethyl ether, ethyl acetate, and hexane were bought as analytical grade (Sigma-Aldrich, Bornem, Belgium). NaOH, HCl, absolute ethyl alcohol, methanol (analytical grade), formic acid, acetonitrile, and acetic acid (glacial) were bought from Merck Co. (Darmstadt, Germany).