## 3 Results
For example, antioxidant capacity detected by ABTS assay has previously been found to be significantly higher for fruits, vegetables and beverages than that by DPPH assay, as also found in the present study, suggesting that the high-pigmented and hydrophilic antioxidants were better reflected by the ABTS assay than the DPPH assay [23]. Nevertheless, the antioxidant capacities by both assays have also been suggested to be more strongly correlated with total phenolics than \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Sample** & **ABTS Value \({}^{\bullet}\) of TACs** & \multicolumn{3}{c}{**ABTS Value of TLCs**} & \multicolumn{3}{c}{**ABTS Value of TLs**} \\ \hline  & min–Max value & Median value & min–Max value & Median value & min–Max value & Median value \\ \hline Apple juice & 47.5–202.7 & 118.2 & 35.5–706.8 & 44.3 & 91.8–909.5 & 153.7 \\ (mg/100 mL juice) & 14.9–22.5 & 20.7 & 20.2–48.2 & 22.9 & 35.2–70.7 & 43.6 \\ \hline \end{tabular}  
* ABTS value is expressed as umol of Trolox equivalent per g of dry weight of extract (umol TE/g of DW).  
\end{table} 
Table 5: Total antioxidant capability of TAC, TLC and TL extracts from apple juice and by-products using the ABTS method. with total flavonoids content, suggesting that not only flavonoids but also non-flavonoid phenolics contribute in the antioxidant effects observed by both assays. The DPPH assay is conventionally conducted under hydroalcoholic conditions, whilst ABTS assay is usually carried out in aqueous conditions. Thus, flavonoids' solubility in both media should be taken into consideration. In addition, the reagents of both assays might have different affinities against other compounds that are present in the samples. Several other bioactive compounds that are also present in an extract like carotenoids that also possess strong antioxidant capacities may not be highly soluble into such reaction medias and thus a disparity of their antioxidant bio-efficacy may be observed due to not being able to express the overall radical scavenging activities of all bioactive compounds present in an extract. Moreover, ABTS and DPPH assays are in vitro models and do not assess all of the antioxidant activities in foods, while antioxidant capacity depends on the extraction methodology applied and solvents used. Both assays are convenient in their application and thus most popular; nevertheless, they are limited as they use non-physiological radicals. Taking into account the state before reaching equilibrium of antioxidants reacting in a complex manner, this approach may introduce a simplified reference to the competing reaction that occurs in reality, and thus be closer to in vivo methodologies that are needed to fully evaluate the antioxidant potency of such natural extracts. Antioxidants' relative capacities to scavenge DPPH and ABTS radicals, mainly in aqueous and hydroalcoholic phases, respectively, are measured by the DPPH and ABTS tests, for example. For instance, the DPPH and ABTS assays measure the free radical scavenging activities, meaning the relative abilities of antioxidants to scavenge the DPPH and ABTS radicals primarily in aqueous and hydroalcoholic phases, respectively. Conversely, the FRAP assay uses antioxidants already present in the samples to reduce ferric iron (Fe\({}^{3+}\)) to ferrous iron (Fe\({}^{2+}\)), thereby measuring the antioxidant potential in the samples. This indicates that the test measures plasma's capacity to reduce ferric acid, which is more similar to the in vivo circumstances present in blood. The FRAP assay also seems to have better specificity in detecting the antioxidant activity of extracts rich in amphiphilic compounds [7; 9], which was also observed in the present study, since, as shown in Table 6, the TAC extracts from both apple juice and by-products (45.8 mg/100 mL juice and 18.7 mg/100 g by-products) had a much stronger antioxidant capacity than their TLC extracts (0.1 mg/100 mL juice and 0.1 mg/100 g by-products).