## 3 Results  
### Total Polyphenol Content and Antioxidant Capacity  
Chestnuts are excellent sources of bioactive compounds and are low in fat content if compared with other nuts (almonds, hazelnuts, and walnuts). Since healthiness has become an important trait that influences the purchase and consumption of food products over recent decades [23], it is relevant to highlight the quality of chestnuts and their potential as functional foods. One of the most important phytochemical classes of secondary metabolites in plants is polyphenols. They are the main group of biologically active non-nutrients detected in plant materials and foods, which have antioxidant, anti-bacterial, and anti-cancer properties, and protective effects against several chronic diseases [24]. Previous studies have reported values ranging from 196 to 431 mg\({}_{\text{GGAE}}\) 100 g\({}^{-1}\) dry weight (DW) in Spanish cultivars [25], a range from 500 to 3282 mg\({}_{\text{GGAE}}\) 100 g\({}^{-1}\) DW in Turkish cultivars [26], and a range from 103 to 219 mg\({}_{\text{GGAE}}\) 100 g\({}^{-1}\) DW in \(C\). _millissima_ cultivars [27], demonstrating a high TPC variability in the fruits of _Castanea_ spp. On the same cultivar, \"Judia\", [PERSON] et al. [28] found that the extracts from the coldest location had 50.5% more total phenolics content than the ones from the hottest location, showing a significant impact of climatic environmental factors on the synthesis of polyphenols. Moreover, most of the genotypes presented polyphenic levels similar to hazelnut ones [29; 30] and higher than walnut ones [31]. In the present study, different cultivars are grown on the same clonal rootstock and in the same pedoclimatic and agronomic conditions to evaluate the genetic differences. Figures 2 and 3 show the total polyphenol content (TPC) and antioxidant capacity (AOC) values for a selection of cultivars. Figures S1 and S2 (Supplementary Materials) report the values for all the analyzed cultivars. The obtained TPC mean values (Figure 2) ranged from 191.44 \(\pm\) 17.95 mg\({}_{\rm{GAA}}\) 100 g\({}^{-1}\) DW, for the flour derived from \"Ruiana\" cv (Piemonte Region), to 28.72 \(\pm\) 16.56 mg\({}_{\rm{GAA}}\) 100 g\({}^{-1}\) DW, for the Tuscan cultivar \"Marrone di Marradi\", in accordance with previous studies [4; 13]. Overall, Japanese chestnut's presented lower values than the other chestnut's (with an average of 59.03 mg\({}_{\rm{GAA}}\) 100 g\({}^{-1}\) DW), followed by the \"marrone-type\" group (e.g., the French cultivar \"Marron de Lyon\" presented a TPC value of 176.26 \(\pm\) 15.44 mg\({}_{\rm{GAA}}\) 100 g\({}^{-1}\) DW, similar to the higher values of sweet chestnut's and Euro-Japanese hybrids). In agreement with [PERSON] et al. [14], \"Marissard\" cv showed the highest TPC value in Euro-Japanese hybrids (163.91 \(\pm\) 15.23 mg\({}_{\rm{GAA}}\) 100 g\({}^{-1}\) DW). It is worth noting that, as the study of Uzun [32] reported, total phenolics decrease during cold storage after the harvesting; therefore, this aspect may have affected the measures. Figure 2: Total polyphenol content of 35 selected chestnut cultivars. Different letters for each cultivar indicate the significant differences at \(p\) < 0.05. Red color: “marrone-type” chestnut (MT); purple colors: sweet chestnut (SC); orange color: Euro-Japanese hybrid (EH); blue color: Japanese chestnut (JC). The dashed line indicates the average. The antioxidant capacity (AOC) is generally due to the content of polyphenols, vitamins, monoterpenes, and organic acids. These free-radical scavenging antioxidants prevent functional loss and damage to biological membranes, detoxify enzymes, maintain health, and reduce the risk of disease [33]. To evaluate this parameter, there are several methods, which give different units of measurement, so it is difficult to compare the values with earlier studies.