Determination of the antiradical activity and kinetics of pomegranate juice using 2,2-diphenylpicyrl-1-hydrazyl as the antiradical probe

Whole fruit pomegranate (Punica granatum L.) juice of the ‘Wonderful’ cultivar was characterized through the elucidation of its antiradical kinetics and activity using 2,2-diphenyl-1-picrylhydrazyl as the antiradical probe. Time-dependent concentration of 2,2-diphenyl-1-picrylhydrazyl during its reduction by the juice has been adjusted through a non-linear parametric fitting. Determined total antiradical activity was high, able to reduce 84.58 µmol/l of 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), equivalent to a concentration of 42.29 mmol/l of ascorbic acid (or Trolox). Partial antiradical activities due to the fast-, medium- and slow-kinetics were 49.09, 18.16 and 17.33 µmol/l of reduced 2,2-diphenyl-1-picrylhydrazyl per concentration unit of juice (µl/ml), respectively. The corresponding rate constant for the fast-, medium- and slow-kinetics were κ₁ = 6.03, κ₂ = 0.169 and κ₃ = 0.0094 (μl l)/(ml µmol min), respectively. This methodology allows characterization of samples through the accurate determination of the kinetics of their antiradical features, avoiding the use of empirical approximations that hinder the realistic comparison between extracts independently of their origin.