Valorization of Avocado Seed Wastes for Antioxidant Phenolics and Carbohydrates Recovery Using Deep Eutectic Solvents (DES)

Abstract

Avocado seeds represent the chief waste produced in avocado processing, leading not only to environmental problems regarding its elimination but to a loss of economic profitability. In fact, avocado seeds are known as interesting sources of bioactive compounds and carbohydrates, so their utilization may reduce the negative effect produced during the industrial manufacture of avocado-related products. In this sense, deep eutectic solvents (DES) are a novel greener alternative than organic solvents to extract bioactive polyphenols and carbohydrates. The study was based on a Box–Behnken experimental design to study the effect of three factors, temperature (40, 50, 60 °C), time (60, 120, 180 min) and water content (10, 30, 50% v/v) on the responses of total phenolic (TPC) and flavonoid content (TFC), antioxidant capacity (measured as ABTS and FRAP) and xylose content in the extract. The DES Choline chloride:glycerol (1:1) was used as solvent on avocado seed. Under optimal conditions, TPC: 19.71 mg GAE/g, TFC: 33.41 mg RE/g, ABTS: 20.91 mg TE/g, FRAP: 15.59 mg TE/g and xylose: 5.47 g/L were obtained. The tentative identification of eight phenolic compounds was assayed via HPLC-ESI. The carbohydrate content of the solid residue was also evaluated, and that solid was subjected to two different processing (delignification with DES and microwave-assisted autohydrolysis) to increase the glucan susceptibility to enzymes, and was also assayed reaching almost quantitative glucose yields. These results, added to the non-toxic, eco-friendly, and economic nature of DES, demonstrate that these solvents are an efficient alternative to organic solvents to recover phenolics and carbohydrates from food wastes.

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

“…In both cases, the DESs screen showed to be efficient and selective towards the target compound. [196] ChCl:GLY (1:1) Avocado Phenolics/Carbohydrates MAE [197] ChCl:GLY (1:2) Kiwifruits Polyphenols UAE [182] ChCl:GLY (1:2) Spice Polyphenols UAE [198] ChCl:ACA (1:4) Tarragon Bioactive compounds CE [199] LAC:GLY (1:2) Foxtail millet Husk Bioactive compounds UAE [173] ChCl:GLY (…”

Natural deep eutectic solvents (NaDES): translating cell biology to processing

“…Poorly water-soluble compounds can be extracted from plant biomass in high concentrations and afterwards separated from the (Na)DES by addition of water and subsequent compound precipitation. Thus, (Na)DES, alone or in combination with other methods, can be used to extract various compounds like polyphenols, 47–51 pigments, 52 enzymes 53 and carbohydtrates. 50 Their high solubilizing capacity can be exploited to overcome limited substrate solubility in enzymatic reactions 54 as well as for separation techniques.…”

“…Thus, (Na)DES, alone or in combination with other methods, can be used to extract various compounds like polyphenols, 47–51 pigments, 52 enzymes 53 and carbohydtrates. 50 Their high solubilizing capacity can be exploited to overcome limited substrate solubility in enzymatic reactions 54 as well as for separation techniques. 55,56 In recent years, companies focused on natural ingredients have already turned their attention on using NaDES as extraction solvents for plant-based active compounds.…”

A Sustainable Extraction Approach of Phytochemicals from Date (Phoenix dactylifera L.) Fruit Cultivars Using Ultrasound-Assisted Deep Eutectic Solvent: A Comprehensive Study on Bioactivity and Phenolic Variability

“…Recently, studies have been published on extracting phenolic compounds from diverse biomass sources and botanical sources using the DES technique [17,[24][25][26][27]. As far as we are aware, there are currently no published studies that examine the retrieval of phenolic compounds from date fruits using the UA-NADES method.…”