Extraction of Antioxidant Phenolics from Agri-Food Waste Biomass Using a Newly Designed Glycerol-Based Natural Low-Transition Temperature Mixture: A Comparison with Conventional Eco-Friendly Solvents

Abstract

A novel natural low transition temperature mixture (LTTM), composed of glycerol and ammonium acetate (molar ratio 3:1), was tested for its efficacy as a solvent in recovering phenolics from chlorogenate-rich agri-food solid wastes, including potato peels (PPs), eggplant peels (EPPs), and spent filter coffee (SFC). The efficacy of this solvent was compared with other eco-friendly solvents, including aqueous glycerol, aqueous ethanol, and water. The LTTM was demonstrated to be by far the most efficient in extracting chlorogenates and superior or equally efficient with the other solvents in recovering flavonoids. LTTM extracts produced from waste were also more potent radical scavengers, but results on the reducing power were inconclusive. Liquid chromatography-diode array-mass spectrometry analysis showed that the polyphenolic profiles of all waste extracts obtained with the LTTM were rich in caffeoylquinic and p-coumaroylquinic acid conjugates.

Ultrasound-Assisted Extraction of Polyphenolic Antioxidants from Olive (Olea europaea) Leaves Using a Novel Glycerol/Sodium-Potassium Tartrate Low-Transition Temperature Mixture (LTTM)

“…On the contrary, the extract obtained with the LTTM displayed significantly lower A AR and P R (p < 0.05), compared with the aqueous methanolic extract (Figure 3). This finding contrasted a general trend observed in studies on LTTM extracts, where increased polyphenol levels were associated with proportional antioxidant activity [5,9,23], but such a phenomenon has been previously seen in OLL extracts, with correlation between Y TP and A AR being low and statistically non-significant [7]. In concurrence with this, a more recent study showed that high Y TP did not fully coincide with high A AR in OLL extracts [25].…”

“…Total polyphenol yield (Y TP ) was determined with the Folin-Ciocalteu methodology [8] and results were expressed as mg caffeic acid equivalents (CAE) per g of dry weight. Total flavonoid yield (Y TFn ) was assayed with AlCl 3 reagent, as previously reported [9] and given as mg rutin equivalents (RtE) per g of dry weight. The antioxidant activity was estimated by determining the antiradical activity (A AR ) and the ferric-reducing power (P R ) of the extracts.…”

Combination of Lactic Acid-Based Deep Eutectic Solvents (DES) with β-Cyclodextrin: Performance Screening Using Ultrasound-Assisted Extraction of Polyphenols from Selected Native Greek Medicinal Plants

“…Yield in total polyphenol (Y TP ) was determined with the Folin-Ciocalteu methodology, as described elsewhere [14]. Yield in total flavonoids (Y TFn ) was determined according to a previously published protocol [15]. The antiradical activity (A AR ) and reducing power (P R ) were determined with well-established methods [16].…”

Low-Transition Temperature Mixtures (LTTMs) Made of Bioorganic Molecules: Enhanced Extraction of Antioxidant Phenolics from Industrial Cereal Solid Wastes

“…Total flavonoid yield (Y TFn ) was assayed with AlCl 3 reagent, as previously reported [12] and given as mg rutin equivalents (RtE) per g of dry weight. Yield in total flavanols (Y TF ) was measured as µg catechin equivalents (CtE) per g of dry weight, following derivatization with DMACA reagent [17].…”

“…Recent investigations with LTTMs composed of glycerol or L-lactic acid (HBD) and sodium acetate (HBA), two low-cost biomolecules, have shown that polyphenol extraction yields were much higher than those obtained with water and were comparable to those obtained with aqueous ethanol [12,13]. On such grounds, the study was carried out to screen combinations of L-lactic acid used as HBD, with the natural amino acids glycine and L-alanine, but also choline chloride, as HBAs ( Figure 1) in an effort to identify (i) pairs that provide stable LTTMs and (ii) LTTMs that can afford high extraction yields of antioxidant phenolics from ICSWs.…”