3.4.1. TEAC Assay

The antioxidant activity against the stable synthetic ABTS radical cation of different HI extracts is depicted in Table 3. This analysis is based on electron transfer reactions in order to assess the radical scavenging activity of several compounds. The highest values for AA were for 50% aqueous acetone extracts, with the strongest activity of 1296.51 ± 19.25 mg TE/g dw involucre (5.18 ± 0.08 mmol TE/g dw involucre). The AA for green leafy cover noticed by Shahidi et al. [14] was 117 μmol TE/g extract after extraction with 80% ethanol, while the values for hazelnut kernel, skin, hard shell, and tree leaf were between 29 and 148 μmol TE/g extract. Alasalvar et al. [29] reported AA values of 1.29 and 1.14 mmol TE/g extract obtained from green leafy cover using 80% acetone and 80% ethanol, respectively. In another source, the antioxidant activities were in the range of 3063–3573 μmol TE/100 g dw natural hazelnuts [41]. The AA of hazelnut by-product extracts was 4–5-fold greater than that of kernel extracts, meaning that hazelnut by-product extracts compared to hazelnut kernel extract would have a stronger antioxidant activity.
