Green-Sustainable Recovery of Phenolic and Antioxidant Compounds from Industrial Chestnut Shells Using Ultrasound-Assisted Extraction: Optimization and Evaluation of Biological Activities In Vitro.

Fátima Lameirão,Francisca Rodrigues,Elsa F Vieira,Diana Pinto,Cristina Freire,Paulo Costa,Stefano Dall’Acqua,Stefania Sut,Andreia F Peixoto,Cristina Delerue-Matos

doi:10.3390/antiox9030267

Abstract

Chestnut processing industry generates large amounts of by-products, including leaves, burs and shells that are a source of bioactive compounds. The purpose of this study was to establish an ultrasound-assisted extraction (UAE) of phenolic and antioxidant compounds from industrial chestnut shells. A central composite design (CCD) was conducted to analyze the effects of time (4–46 min) and temperature (34–76 °C) in the antioxidant activity (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and ferric reducing antioxidant power (FRAP)) and total phenolic compounds (TPC) of chestnut shells extracts. The optimal extraction conditions were obtained at 70 °C for 40 min. The optimal extract was characterized regarding phenolic profile, radical scavenging capacity, and effects on intestinal and dermal cell lines. The optimal extract revealed high amounts of ellagic acid (40.4 µg/mg dw), followed by caffeic acid derivative (15.4 µg/mg dw) and epigallocatechin (15.3 µg/mg dw). Indeed, the extract exhibited the highest scavenging efficiencies against NO● (IC50 = 0.1 µg/mL) and HOCl (IC50 = 0.7 µg/mL) and did not conducted to a decrease on HaCaT and HFF-1 viability up to 100 μg/mL. Oppositely, a decrease on Caco-2 and HT29-MTX viability was observed. This study suggests that UAE could be a sustainable option to valorize chestnut shells as raw material for different industries.

Highlights

Castanea sativa Mill. is a species belonging to Fagaceae family and genus Castanea widely present in Europe
The extractive process is an essential step in the recovery and purification of bioactive compounds from plant matrices [33]
Regarding the evaluated activities of the extracts, Total Phenolic Content (TPC) ranged from 255.8 mg gallic acid equivalents (GAE)/g dw to 418.0 mg GAE / g dw; Ferric Reducing Antioxidant Power (FRAP) varied between 28.7 μg/mL and 45.3 μg/mL; DPPH ranged from 43.7 μg/mL to 63.7 μg/mL; ABTS ranged from 50.5 μg/mL to 88.0 μg/mL

Summary

Introduction

Castanea sativa Mill. is a species belonging to Fagaceae family and genus Castanea widely present in Europe. Chestnut wood is rich in tannins and extremely resistant. It is commonly employed in the manufacture of barrels and casks due to its low porosity and sensitivity to temperature variation. The high levels of aldehydes, phenolic, and volatile compounds are extremely important in the wine aging process [2]. The fruits are sorted, manually checked and frozen. During this process, several by-products are generated, mainly shells (inner and outer). Outer and inner shells represent, respectively, 1.5–8.9% and 6.3–10.1% of the total weight of fresh fruit [3]. The main phenolic compounds present in chestnut shells are phenolic acids (ellagic and gallic), flavonoids (rutin, quercetin and apigenin), and tannins [3,4,5]

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