Food-Waste Valorisation: Synergistic Effects of Enabling Technologies and Eutectic Solvents on the Recovery of Bioactives from Violet Potato Peels

Abstract

The recovery of valuable bioactive compounds from the main underutilised by-products of the food industry is one of the greatest challenges to be addressed in circular economy. Potato peels are the largest waste generated during potato processing. However, they could be a potential source of valuable bioactive compounds, such as polyphenols, that can be reused as natural antioxidants. Currently, environmentally benign enabling technologies and new types of non-toxic organic solvents for the extraction of bioactive compounds may dramatically improve the sustainability of these processes. This paper focuses on the potential inherent in the valorisation of violet potato peels (VPPs) by recovering antioxidants using natural deep eutectic solvents (NaDES) under ultrasound (US)- and microwave (MW)-assisted extraction. Both the enabling technologies provided performances that were superior to those of conventional extractions in terms of antioxidant activity determined by the DPPH· (2,2-diphenyl-1-picrylhydrazyl) assay. In particular, the most promising approach using NaDES is proven to be the acoustic cavitation with a Trolox eq. of 1874.0 mmolTE/gExtr (40 °C, 500 W, 30 min), vs. the 510.1 mmolTE/gExtr of hydroalcoholic extraction (80 °C, 4 h). The shelf-life of both hydroalcoholic and NaDES-VPPs extracts have been assessed over a period of 24 months, and found that NaDES granted a 5.6-fold shelf-life extension. Finally, the antiproliferative activity of both hydroalcoholic and NaDES-VPPs extracts was evaluated in vitro using the MTS assay on human tumour Caco-2 cells and normal human keratinocyte cells (HaCaT). In particular, NaDES-VPPs extracts exhibited a significantly more pronounced antiproliferative activity compared to the ethanolic extracts without a noteworthy difference between effects on the two cell lines.

A Comprehensive Review on Deep Eutectic Solvents and Its Use to Extract Bioactive Compounds of Pharmaceutical Interest

“…The extracts with DESs also presented better results in terms of antimicrobial activity [170,179,184], antiproliferative activity in tumour Caco-2 cells and normal human keratinocyte cells [185], lower toxicity and increase bioavailability of the target compounds when administered to rats [186], higher antioxidant, [184] and anti-inflammatory effects as well as inhibitory effects against αglucosidase and pancreatic lipase [187] when compared to the extracts from the traditional solvents. The enhanced biological activity of the DESs extracts can be explained by the higher content of bioactive compounds [187,188].…”

A Comprehensive Review on Deep Eutectic Solvents and Its Use to Extract Bioactive Compounds of Pharmaceutical Interest

“…The extracts with DESs also presented better results in terms of antimicrobial activity [ 165 , 174 , 179 ], antiproliferative activity in tumour Caco-2 cells and normal human keratinocyte cells [ 180 ], lower toxicity and increased bioavailability of the target compounds when administered to rats [ 181 ], higher antioxidant effects [ 179 ], and higher anti-inflammatory effects, as well as inhibitory effects against α-glucosidase and pancreatic lipase [ 182 ] when compared to the extracts from the traditional solvents. The enhanced biological activity of the DESs extracts can be explained by the higher content of bioactive compounds [ 182 , 183 ].…”

“…Another important advantage of the extracts containing DESs is their stability. Some studies were performed to study this parameter and found that the DESs extracts have a longer shelf-life when compared with conventional solvents extracts [ 129 , 180 ]. This stabilization was due to the ability of the DESs to stabilize the phenolic compounds [ 185 ].…”

Green Extraction of Polyphenols via Deep Eutectic Solvents and Assisted Technologies from Agri-Food By-Products

“…Tomato is rich in flavones like chlorogenic acid, rutin, and quercetin [44,61]. Numerous phenolic compounds have been extracted from onion and tomato by-products using DESs, such as quercetin [58,60], kaempferol glycosides [59], and anthocyanins [62]. Additionally, DESs show high extraction efficiency in retrieving phenolic compounds from other vegetable by-products, like kale waste [63], bitter melon leaves [64], pepper leaves [65], and lotus leaves [66].…”