## 1 Introduction  
The sweet chestnut tree (_Castanea sativa_ Mill. ), which belongs to the Fagaceae family, is widely distributed in European countries, Italy, Spain, France, Greece, Portugal and Turkey: it is a source of wood, fruit, honey and waste material for tannins [1, 2]. Over the last decade, the chestnut sector has constantly grown in Europe, since fruits, mainly consumed boiled or roasted, are an excellent source of energy, due to their high starch content, minerals (K, Mg, Mn, and Cu), unsaturated fatty acids (omega-3), fiber and vitamins E and C [3, 4]. A variety of preparations have been added to the traditional use of the fruit: marron glace, pureses, frozen nuts, and jams, and, more recently, different gluten-free products based on chestnut flour for celiac patients [5, 6]. Burrs, leaves and the residue of chestnut processing generates a large amount of waste material, about 15% of the total production. Inner and outer shell resulting from chestnut peeling, represents about 20% of the total fruit weight [5]. This residue, habitually burned as fuel in factories, is the target of new strategies of value assessment and reuse: heavy metal absorbents or wood adhesives, raw materials for lignin and bioethanol production and pigment source for dyeing [7; 8]. At present, there are new attractive applications for utilizing chestnut waste as a source of bioactive compounds with health effects [9]; the chestnut pericarp (CP) (outer shell; husk) and integument (inner shell; pellicle) are a rich source of nutraceuticals, ascorbic acid, carotenoids, phenolics like gallic and ellagic acid, flavonoids and condensed tannins, with antioxidant, antimicrobial, and anticancer properties [4; 10; 11; 12]. The _green_ recovery of these bioactive compounds from chestnut shell is important, both to preserve their health properties for food, cosmetics and pharmaceutical industries and, to reduce the environmental impact of organic solvents [6]. Hence the decision to use, in this work, only deionized water as an extractant of phenolic compounds. Cold and hot water, alone or in combinations with organic solvents, has been employed by our group, with different purposes and on different matrices, since 2010 [13; 14; 15; 16; 17], but this work is the first on chestnut. Other researchers used cold water with Na\({}_{2}\)SO\({}_{3}\) and NaOH to extract phenolic compounds, tannins and ellagitannins from Portuguese chestnut peels [18]; bur and shell extracts of _Castanea sativa_ were obtained using water and hydroalcoholic solutions at 25, 50 and 75 \({}^{\circ}\)C to make the extraction faster, selective, and more effective [19]; [PERSON] et al. [20] used water and a variety of organic solvents, at 60 \({}^{\circ}\)C, to extract polyphenols from inner shells of Japanese chestnut (_Castanea crenta_). Other authors used boiling water to maximize the recovery of bioactive compounds from inner and outer shells of Italian chestnut [21; 22]. The use of water alone as a solvent is expected to provide extracts with a lower yield of phenolic compounds than organic solvents or hydroalcoholic mixtures [19]. The chemical composition of these extracts, their antioxidant and antitumoral properties, that are the subject of this research, are also expected to change [19; 20; 23]. In this work, the total phenol content (TP) and the antioxidant capacity of chestnut extracts have been determined by Folin-Ciocalteu and DPPH, ABTS and FRAP assays. Furthermore, according to recent studies on outer shell extracts [24] and other plant and fruit extracts [25; 26], a direct electrochemical determination of TP and antioxidant capacity was also provided, since the method is particularly effective in the particular case of polyphenols extracts [27]. The redox properties of single molecules, such as gallic, ellagic and tannic acid, were also investigated [28; 29].