## 3 Results
### Phytochemical Composition and Nutritional Properties  
The phenolic compounds were grouped into the following classes to define the contribution of each class to the total polyphenolic composition: benzoic acids (ellagic acid and gallic acid), cinnamic acids (caffeic, coumaric, ferulic, and chlorogenic acids), catechins (catechin and epicatechin), flavonols (hyperoside, isoquercitin, quercetin, quercetin, and rutin), and tannins (castalagin and vescalagin). Quercetin and quercitin were not detected in chestnut extracts, whereas gallic acid was only quantified in very small amounts in the Japanese cultivar \"Ginyose\". The complete phytochemical composition in chestnut extracts is shown in Table S2 (Supplementary Materials). The results showed a predominance of cinnamic acids in comparison to flavonoids (Table S2) in all the analyzed chestnut groups. European chestnuts presented the highest values of cinnamic acids, in particular, the sweet chestnut cultivar \"Pugnenga\" (62.89 \(\pm\) 0.22 mg 100 g\({}^{-1}\) DW). Generally, chlorogenic acid was the main component, as reported in Figure 4, except in \"Ishizuki Tardiva\" (in this cultivar, it was not detected). The mean amount of chlorogenic acid in Euro-Japanese hybrids (10.88 mg 100 g\({}^{-1}\) DW) was higher than the data reported by [PERSON] et al. [14] for the same cultivars, suggesting that the geographic location played a significant role. This compound can be also found in green coffee extracts and tea, and it has been investigated in several medical studies. It was demonstrated that chlorogenic acid is an antioxidant agent and it can perform crucial roles in lipid and glucose metabolism regulation, contributing to weight reduction and the prevention of obesity-related diseases [35]. Flavonols, mainly hyperoside, were detected in trace amounts or were absent in Japanese chestnuts, as well as in Euro-Japanese hybrids; significant amounts were only identified in \"Lusenta\" cv. On the other hand, the class was detected, although in low amounts, in most of the European chestnuts. Hyperoside seems to be an effective protection against inflammatory vascular damage; thus, it may be useful in the treatment of severe vascular inflammatory diseases such as septic shock [36]. Benzoic acids (Table S2) were only represented by ellagic acid, and they are the class that mostly differentiated the cultivars within the \"marrone-type\" group. Ellagic acid was almost absent in the Japanese cultivars; the Euro-Japanese hybrids with the highest amounts were \"Marlhac\" and \"Vignols\" cv, whereas this compound was detected in trace amounts in \"Maridonne\" and \"Precoce Migoule\" cv. The highest values were identified in _C. sativa_ cultivars, in particular, in \"Rossane\" (26.73 \(\pm\) 0.02 mg 100 g\({}^{-1}\) DW), but also in \"Contessa\", \"Neirana\", \"Pugnenga\", \"Ruiana\", and \"Tarviso\" cv. Benzoic acids are very important compounds in human nutrition because of their anti-cancer, anti-atherosclerotic, anti-inflammatory, anti-Hepatotoxic, and anti-HIV properties [37]. Catechin and epicatechin (Table S2), molecules involved in the inhibition of lipid peroxidation and the prevention of oxidative stress-induced diseases [38], were quantified in different proportions: in European chestnuts, the two compounds were present in similar amounts, whereas in other cases, they presented different levels. They represented an important class, not only in terms of their contribution to the total polyphenol content, but also as markers to distinguish the several cultivars. The Japanese cultivar \"Ginyose\" showed a very high value (73.09 \(\pm\) 4.26 mg 100 g\({}^{-1}\) DW) compared to the other ones. The main tannins detected in _Castanea_ ssp. (Table S2, Figure 5) are hydrolysable elimgativins (castalagin and vescalagin), which are effective antagonists against viruses, bacteria, and eukaryotic microorganisms [39]. The Euro-Japanese hybrids showed very high amounts of tannins, especially \"Vignols\" (34.97 \(\pm\) 0.24 mg 100 g\({}^{-1}\) DW), \"Lusenta\", and \"Maridone\" cv.