4.5. Analysis of Antioxidant Activity and Total Phenolic Compounds

Antioxidant activity was measured by three different methods: FRAP [18], DPPH [50], and ABTS assay [51]. In addition, the content of total phenolic compounds (TPC) was investigated by the Folin–Cocialteu method as described by Stratil et al. [52]. The values of antioxidant activity determined by FRAP, DPPH, and ABTS methods are expressed as mmol of Trolox equivalents per 1 L of tested extracts (mmol TE/L). The results of the total polyphenol content are expressed as 1 mg of gallic acid equivalents per 1 L (mg GAE/L) of tested extracts. All measurements were performed using Spectrophotometer UV-VIS Metash UV 5100 (Shanghai Metash Instruments, Shanghai, China) with MetaSpec Pro software (Shanghai Metash Instruments, Shanghai, China).