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. 2019 Jul 13;8(7):222. doi: 10.3390/antiox8070222

Figure 2.

Figure 2

Antiradical capacity and redox properties of pBeet, mepBeet, m-OH-pBeet and m-OH-mepBeet. (a) Colored contour map of Trolox equivalent antioxidant capacity (TEAC) of the betalains as a function of the pH (x-axis) and reaction time (y-axis). Red to blue color gradient indicating high to low (5.6 to −1.4) TEAC; selected TEAC contour values are indicated on the surface for clarity. Raw data is presented in Table S1. Reaction conditions: Britton–Robinson (BR) buffer (40 mmol L−1), [ABTS+•] = 46.7 μmol L−1, [Trolox]: 0.5–4 μmol L−1, [betalain]: 0.3–1.5 μmol L−1, at 25 ± 1 °C. (b) Dependence of the electrode potential (Ep) of the betalains on the pH (BR buffer). Straight lines show linear regressions (confidence interval of 95%, red for anodic and blue for cathodic peaks); numbers in brackets are the proton to electron ratio. Cyclic voltammograms are presented in Figure S10.