## 4 Biological Properties of _P. avium_ L. By-Products
### Antioxidant Activity
\begin{table}
\begin{tabular}{p{56.9 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline \hline
**Part of Plant** & **Extract** & **Type of Study** & **Main Outcomes** & **References** \\ \hline \multirow{3}{*}{Stems} & \multirow{3}{*}{Aqueous acetone 70\% scavenging activity} & DPPH free radical scavenging activity & Genotypes with highest phenolic content possess higher DPPH scavenging activity. & [74] \\ \hline \multirow{3}{*}{Stems} & \multirow{3}{*}{Hydroxymethanolic 80:20 (\(v/v\)) Aqueous infusion} & DPPH free radical scavenging activity & All preparations revealed a strong antioxidant activity, but the hydrothermal extract was the most relevant; The antioxidant potential is probably correlated with phenolic content. & [12] \\  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \cline{1-1}  & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Antioxidant activity of _Prunus avium_ L by-products. To determine the total antioxidant activity of flavonoids extracted from cherry stems through two different extraction methods (conventional and ultrasound-assisted extraction), [PERSON] et al. [75] used the 2,2'-azino-bis-3-ethylben-zothiazoline-6-sulphonate (ABTS\({}^{\bullet+}\)) radical cation assay. The obtained results showed that stem extracts possess great antioxidant potential. The extraction method used affected the IC\({}_{50}\) values of total antioxidant activity due to their yield in flavonoid extraction [75]. In this study, it was found that the antioxidant activity depends on the synergetic effects among different phenolics. Higher contents of phenolic compounds such as sakuranetin, isosakuranetin, neochlorogenic and chlorogenic acid, catechin and the epicatechin derivative, and _p_-coumaric acid and the _p_-coumaroylquinic acid derivative all lead to greater antioxidant activity. More recently, in a study conducted by [PERSON] et al. [7], the antioxidant activity of hydroethanolic extracts and infusions of _P. avium_ leaves, stems, and flowers were evaluated through DPPH free radical scavenging, and the other radicals such as O\({}_{2}\)\({}^{\bullet-}\) and \({}^{\bullet}\)NO. The DPPH method showed that the hydroethanolic extract of stems was the most active (IC\({}_{50}\) = 22.37 \(\pm\) 0.29 \(\mu\)g/mL), while the scavenging activity of \({}^{\bullet}\)NO was more effective in the infusion of this by-product (IC\({}_{50}\) = 99.99 \(\pm\) 1.89 \(\mu\)g/mL). The evaluation against O\({}_{2}\)\({}^{-}\) showed that the hydroethanolic extract of leaves was noteworthy among the others (IC\({}_{50}\) = 9.11 \(\pm\) 0.16 \(\mu\)g/mL) [7]. In this study, a positive correlation was detected between the activity of _P. avium_ stems against DPPH radicals and the total phenolic acids (r = 0.9767), and also their potential against \({}^{\bullet}\)NO and total phenolics and total amount of flavonoids (r = 0.9575 and r = 0.9537, respectively). These results could be related to the chemical structure of identified phenolics due to their richness in hydroxyl groups (OH). Similarly, in another study, the aqueous infusion and the hydroethanolic extract of the stems, leaves, and flowers of _P. avium_ were compared according to their free radical scavenging capacity [10]. The results showed that the hydroethanolic extracts of stems exhibited the strongest antioxidant activity in the DPPH assay, followed the aqueous infusion (IC\({}_{50}\) = 19.04 \(\pm\) 0.3 and IC\({}_{50}\) = 28.41 \(\pm\) 0.55 \(\mu\)g/mL, respectively). Moreover, after comparing the different extracts of cherry by-products, _P. avium_ leaves showed better antioxidant activity than flowers [10]. In sum, _P. avium_ by-products such as sweet cherries may be a new promising source of phenolic compounds, given that they have already been proven to possess considerable antioxidant activity.