Development and Box-Behnken design optimization of a green extraction method natural deep eutectic solvent-based for phenolic compounds from barley malt rootlets.

In recent years, attention has been turned finding new sources of phenolic compounds, antioxidant molecules, main by-products from the agri-food chain like barley malt rootlets (BMRs). Traditionally, phenolic compounds are extracted from food matrices using different procedures, for example, solid-liquid, liquid-liquid, or solid-phase extraction techniques employing organic solvents. With the advent of green chemistry, attention has been paid to the search for green, nontoxic, inexpensive, and nonflammable solvents and the natural deep eutectic solvents (NADESs) respect these characteristics. The aim of this project was to develop and optimize an environmentally friendly, inexpensive, and rapid extraction method for phenolic compounds from BMRs using natural DESs as extractive solvents. Several natural DESs were tested as extractive solvents and, among them, the best results in terms of total phenolic content were obtained using a choline chloride-malic acid (1:2 molar ratio)-based mixture. Box-Behnken experimental design guaranteed the extraction of 9.51 ± 0.83 gallic acid equivalent/g of BMRs, under the following optimal extraction conditions: 1:21 solid-to-liquid ratio, 80°C as extraction temperature, 43 min as the time of extraction, and 29% as a percentage of added water in the NADESs. Phenolic acids and flavonoids were detected in the BMRs extract through HPLC-PDA/MS analysis.

Choline-chloride and betaine-based deep eutectic solvents for green extraction of nutraceutical compounds from spent coffee ground.

Coffee beans contain several compounds which have shown nutraceutial properties; among them chlorogenic acids (CGAs) are the most studied, have shown nutraceutical properties. These molecules are also present in the waste by-product known as spent coffee grounds (SCG). SCG are generated during the production of coffee drink, whereby roasted, ground coffee beans are heat or steam treated. A HPLC-PDA/ESI-MS method has been developed for the analysis of the most representative CGAs in SCG samples using a green extraction approach based on deep eutectic solvents (DESs). We examined fifteen different DESs based on choline chloride and betaine as hydrogen bond acceptor in combination with different hydrogen bond donors being seven alcohols, two organic acids, one sugar and urea. Fifteen CGAs were detected, identified and quantified for the evaluation of extraction efficiency. A betaine-based DES with triethylene glycol (molar ratio 1:2) was the most effective one at extracting CGAs from SCG also compared to a conventional organic solvent. Thirty percent of water added to DES and sample to solvent ratio 1:15 (g/mL) were selected as the best extraction conditions. The chromatographic method was validated studying LOD, LOQ, retention time and peak area precision, and linearity range. Retention time and peak area repeatability were determined obtaining RSDs values below 0.63 % and 8.51 %, respectively. Inter-day precision was determined obtaining RSDs value below 0.58 % and 8.80 % for retention time and peak area, respectively.

Extraction, Analysis, and Antioxidant Activity Evaluation of Phenolic Compounds in Different Italian Extra-Virgin Olive Oils.

The analysis of phenolic compounds in extra virgin olive oils was carried out by high-performance liquid chromatography utilizing photodiode array and mass spectrometry detectors. The chromatographic profile of thirty samples from four Italian Regions highlighted the presence of secoiridoids, phenolic alcohols, flavonoids, and phenolic acid classes. A similar qualitative profile was observed with some differences in peak area and fifteen compounds were tentatively identified. Quantitative analysis was performed by UV detection considering eight standard phenolic compounds. The chromatographic method, after optimization, was validated studying some parameters, e.g., intra-day and inter-day retention time precision, limit of detection, limit of quantification, and linearity. Recovery of the method was performed achieving good results (10 and 50 g·g-1 with recovery of 72.9⁻92.1% (w/w) and 79.1⁻102.8% (w/w), respectively). In all samples secoiridoids were the main compounds ranging from 85 to more than 99% (w/w) of the total concentration of detected phenolic compounds while phenolic acids accounted for the lowest percentage (0.1⁻0.6%, w/w). Finally, total concentration of phenolic compounds and antioxidant activity were determined with different chemical assays. A good and significant correlation among total phenolic compound concentration and antioxidant activity was observed. A significant different phenolic compound concentration and antioxidant activity was determined between samples from Puglia and Sicily. This was studied performing statistical analysis by one-way analysis of variance (ANOVA) followed by Bonferroni post-hoc test.