## 4 Biological Properties of _P. avium_ L. By-Products
### Anti-Hyperglycemic Activity
#### 4.2.1 In Vitro and In Vivo Studies  
Currently, one of the therapeutic strategies for controlling postprandial hyperglycemia is based on the inhibition of \(\alpha\)-glucosidase and \(\alpha\)-amylase, resulting in the delay of car bohydrate digestion into absorbable monosaccharide, thus decreasing hyperglycemia levels [78]. The anti-hyperglycemic potential of _P. avium_ by-products from the Saco cultivar of the Fundao region (Portugal) was supported by the inhibition of \(\alpha\)-glucosidase native activity [7]. The evaluated infusions and hydroethanolic extracts of cherry leaves, stems, and flowers presented different activities in a concentration-dependent manner. The results showed that the infusion and hydroethanolic extract of stems were the most active (IC\({}_{50}\) = 3.18 \(\pm\) 0.23 ug/mL and 7.67 \(\pm\) 0.23 ug/mL, respectively), followed by the hydroethanolic extracts of leaves and flowers (IC\({}_{50}\) = 15.61 \(\pm\) 0.48 and 59.83 \(\pm\) 0.68 ug/mL, respectively) [7]. In the same study, it is reported that these by-products present high phenolic acid content and have been described as \(\alpha\)-glucosidase and \(\alpha\)-amylase inhibitors [76]. Caffeic, ferulic, gallic, and protocatechuric acids are found in _P. avium_ fruits and their by-products [10; 12; 18]. In a study developed by [PERSON] et al. [79] on high-fructose diet-induced metabolic syndrome in rats, the authors showed that these phenolic acids could decrease hyperglycemia after three weeks of treatment. Furthermore, these compounds were also responsible for restoring lipid parameters, indices of atherosclerosis indexes, and cardiovascular parameters to normal values [79]. The increase of oxidative stress was also reverted by these phenolic acids [79]. In a study developed by [PERSON] et al. [6] on sweet cherry fruits of different cultivars, the obtained results showed that all extracts of cultivars were able to inhibit \(\alpha\)-glucosidase in a dose-dependent manner, with IC\({}_{50}\) values ranging from 10.25 \(\pm\) 0.49 to 16.31 \(\pm\) 0.71 ug/mL [6]. Posteriorly, the same authors once again proved the inhibitory capacity of the _P. avium_ fruit against this enzyme of the cultivar most consumed and appreciated in Portugal (i.e., Saco) [5]. The verified differences among diverse cherry cultivars and their by-products may be due to each sample's phenolic composition in the study. Moreover, the authors demonstrated that the ability to inhibit this enzyme by the sweet cherry is more significant than that observed in hydroethanolic extracts of other red fruits [80; 81]. Nevertheless, a direct relationship between the concentration of phenolic compounds and the anti-hyperglycemic activity was observed in the experiments [5; 6; 7]. Regarding \(\alpha\)-amylase, the cyanidin-3-rutinoside inhibited this enzyme, suggesting a potentially useful compound for controlling post-prrandial hyperglycemia [82]. This compound is one of the main anthocyanins found in considerable amounts in sweet cherries [18]. Worthy of note is that cyanidin-3-rutinoside was also detected in _P. avium_ leaves for the first time [10]. These results indicate the potential use of _P. avium_ fruits and their leaves in lowering the post-prandial enhancement of blood glucose levels.