## 4 Biological Properties of _P. avium_ L. By-Products
### Antioxidant Activity  
The interest in phenolic compounds as a source of natural antioxidants has been increasing in the last years due to its beneficial effects in preventing the progression of many diseases such as DM [19]. Oxidative stress plays a crucial role in the development of this disease once the hyperglycemic state is associated with an overproduction of ROS such as hydroxyl radicals (**\"**OH), hydrogen peroxide (H\({}_{2}\)O\({}_{2}\)), superoxide ion (O\({}_{2}^{-}\)), and RNS as nitric oxide radical (\"NO) [70; 71]. These radicals are responsible for inducing lipidic peroxidation, resulting in the damage of lipids, lipoproteins, and membranes, and causing DNA mutations [71], which can lead to the development of other diseases such as multiple sclerosis and cancer [72]. Bioactive compounds present in _P. avium_ by-products possess high antioxidant potential towards free radicals, which has been evaluated through different in vitro assays that include free radical scavenging ability, the chelation of metal ions, and the inhibition of lipid peroxidation [7; 12; 13; 73; 74]. Several researchers have evaluated the antioxidant potential of extracts or the main isolated compounds from _P. avium_ L. by-products. Table 4 summarizes the results of main studies that revealed evidence for the potent antioxidant activity of cherry stems, leaves, and flowers. In a study conducted by [PERSON] et al. [74], the antioxidant activity of seventeen different cultivars of _P. avium_ stems was evaluated, measuring the scavenging activity on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals. The obtained results showed that significant differences exist in the phenolic content of different genotypes, and consequently, differences in the scavenging activity of DPPH-radicals [74]. The extracts from all cultivars showed high antioxidant potential, with DPPH-values ranging from 29.88% to 86.94%. As expected, the genotypes with the highest amounts in phenolic compounds showed thehighest DPPH-radical scavenging activity [74], demonstrating the relationship between phenolic content and antioxidant activity. In another study developed by [PERSON] et al. [12], the antioxidant activity of the hydromethanolic extract, infusion, and decoction of _P. avium_ stems were screened by four different methods: DPPH free radical scavenging, ferric reducing antioxidant power (FRAP) assay, system \(\beta\)-carotene/linoleic acid assay, and thiobarbituric acid-reactive substances (TBARS) assay. In this study, all the preparations of cherry stems presented strong antioxidant potential, with particular emphasis on the hydromethanolic extract. The EC\({}_{50}\) values of the studied preparations ranged from 0.36 to 0.63 mg/mL for DPPH, 0.18 to 0.44 mg/mL for FRAP, 0.30 to 0.42 mg/mL for lipid peroxidation, and 0.07 to 0.24 mg/mL for TBARS [12]. In the same study, _P. avium_ stems revealed the highest antioxidant potential when compared to sweet cherry fruit extracts, probably due to a higher amount of phenolic acids and flavonoids found in this by-product [12]. According to the literature, hydroxycinnamic acids and total flavonoids correspond to about 9.4% and 89.8% of total phenolic compounds contained in the hydroethanolic extract of _P. avium_ stems, with 3-O-caffeoylquinic acid being the main one [7; 12].