A Joint Approach of Morphological and UHPLC-HRMS Analyses to Throw Light on the Autochthonous ‘Verdole’ Chestnut for Nutraceutical Innovation of Its Waste

Abstract

Nowadays, chestnut by-products are gaining a lot of interest as a low-cost raw material, exploitable for developing added-value products. This is in line with suitable chestnut by-products’ management, aimed at reducing the environmental impact, thus improving the chestnut industry’s competitiveness and economic sustainability. In this context, with the aim of valorizing local cultivars of European chestnuts (Castanea sativa Mill.), our attention focused on the Verdole cultivar, which has been characterized by using the UPOV guidelines for its distinctness, homogeneity, and stability. After harvesting, Verdole chestnuts were properly dissected to collect the outer and inner shells, and episperm. Each chestnut part, previously crushed, shredded, and passed through diverse sieves, underwent ultrasound-assisted extraction. The extracts obtained were evaluated for their total phenolic, flavonoid, and tannin content. The antiradical capacity by DPPH and ABTS assays, and the Fe(III) reducing power, were also evaluated. Although all the samples showed dose-dependent antioxidant efficacy, plant matrix size strongly impacted on extraction efficiency. LC-HRMS-based metabolic profiling highlighted the occurrence of different polyphenol subclasses, whose quantitative ratio varied among the chestnut parts investigated. The outer shell was more chemically rich than inner shell and episperm, according to its pronounced antioxidant activity. The polyphenol diversity of Verdole by-products is a resource not intended for disposal, appliable in the nutraceutical sector, thus realizing a new scenario in processing chestnut waste.

‘Sorrento’ and ‘Tulare’ Walnut Cultivars: Morphological Traits and Phytochemical Enhancement of Their Shell Waste

“…In the past, the recovery of bioactive compounds from agricultural waste was carried out using conventional techniques that required long extraction times and a large amount of organic solvents but would damage to heat-sensitive compounds [ 47 ]. Nowadays, new eco-friendly and sustainable techniques have been proposed for the extraction of bioactive compounds with beneficial health effects, leading to an improvement in the yield and chemical compositional profile of the produced extracts [ 48 , 49 ]. Herein, ultrasound-assisted extraction (UAE) was applied to reduce extraction times, lower solvent consumption, and improve extraction rates and extract composition.…”

“…Particle size is one of the parameters that influences the efficiency of UAE. In several studies, particle size reduction by grinding agricultural waste samples improved the extraction efficiency due to increased solvent penetration and solute diffusion [ 30 , 48 , 51 , 53 ].…”

“…Four shells fractions were extracted using the same method described by Ferrara et al [ 48 ], and the extraction percent yield was determined. All obtained samples were stored at 4 °C until further analysis.…”

“…The scavenging ability of the alcoholic extracts obtained by the four shells’ particle size fractions were evaluated for 2,2-diphenyl-1-picrylhydrazyl acid (DPPH) and 2,2-azinobis-(3-ethylbenzothiazolin-6-sulfonic acid (ABTS). DPPH and ABTS assay were carried out according to Ferrara et al [ 48 ]. The DPPH alcoholic solution (9.4 × 10 −5 M) was added to shell walnut extracts in order to reach final concentration levels equal to 1, 5, 10, 50, 100, and 200 µg/mL.…”

“…Condensed tannins were recorded in shell walnut extracts according to Ferrara et al [ 48 ]. The absorbance was read at 550 nm.…”