The Antidiabetic Effect of Grape Pomace Polysaccharide-Polyphenol Complexes

Type 2 diabetes mellitus (T2DM) is one of the most prevalent chronic metabolic diseases of the 21st century. Nevertheless, its prevalence might be attenuated by taking advantage of bioactive compounds commonly found in fruits and vegetables. This work is focused on the recovery of polyphenols and polysaccharide–polyphenol conjugates from grape pomace for T2DM management and prevention. Bioactives were extracted by solid–liquid extraction and by pressurized hot water extraction (PHWE). Polyphenolic fraction recovered by PHWE showed the highest value for total phenolic content (427 mg GAE.mg−1), mainly anthocyanins and proanthocyanidins, and higher antioxidant activity compared to the fraction recovered by solid–liquid extraction. Polysaccharide–polyphenol conjugates comprehended pectic polysaccharides to which approximately 108 mg GAE of phenolic compounds (per mg fraction) were estimated to be bound. Polyphenols and polysaccharide–polyphenol conjugates exhibited distinct antidiabetic effects, depending on the extraction methodologies employed. Extracts were particularly relevant in the inhibition of a-glucosidase activity, with free polyphenols showing an IC50 of 0.47 mg.mL−1 while conjugates showed an IC50 of 2.7, 4.0 and 5.2 mg.mL−1 (solid–liquid extraction, PHWE at 95 and 120°C, respectively). Antiglycation effect was more pronounced for free polyphenols recovered by PHWE, while the attenuation of glucose uptake by Caco-2 monolayers was more efficient for conjugates obtained by PHWE. The antidiabetic effect of grape pomace bioactives opens new opportunities for the exploitation of these agri-food wastes in food nutrition, the next step towards reaching a circular economy in grape products.

Kinetic modelling of the solid–liquid extraction process of polyphenolic compounds from apple pomace: influence of solvent composition and temperature

This study aims to assess kinetic modelling of the solid–liquid extraction process of total polyphenolic compounds (TPC) from apple pomace (AP). In this regard, we investigated the effects of temperature and solvent (i.e. water, ethanol, and acetone) on TPC extraction over various periods. The highest TPC yield of 11.1 ± 0.49 mg gallic acid equivalent (GAE)/g db (dry basis) was achieved with a mixture of 65% acetone–35% water (v/v) at 60 °C. The kinetics of the solvent-based TPC extraction processes were assessed via first-order and second-order kinetic models, with an associated investigation of the kinetic parameters and rate constants, saturation concentrations, and activation energies. The second-order kinetic model was sufficient to describe the extraction mechanism of TPC from AP. This study provides an understanding of the mass transfer mechanism involved in the polyphenolic compound extraction process, thus facilitating future large-scale design, optimization, and process control to valorize pomace waste. Graphical Abstract

Nanomicellar Extraction of Polyphenols—Methodology and Applications Review

The selection of the appropriate extraction method is crucial, especially for the receiving of active substances from plant material. The extraction using supercritical liquids and micellar-mediated extraction (MME) is the most advantageous among the alternative methods to classical solid–liquid extraction. However, the latter seems to be the best solution when the desired actives are polar. The following article presents a comprehensive review of the micellar-mediated extraction method in the last decade. The theoretical principle of the process was also refreshed and the current state of knowledge on the applications for analytical and manufacturing purposes was summarized.

Optimization of conventional solid-liquid extraction and microwave-assisted extraction of polyphenols and antioxidant compounds of blueberry (Vaccinium corymbosum) pomace through response surface methodology

BACKGROUND: Blueberries contain large amounts of phenolic compounds as well as a higher concentration of anthocyanins than other berries. The peel of these fruits contains most of the anthocyanins and therefore pomace is left with the largest quantity of valuable phenolic compounds. Extraction is the most critical step to obtain such compounds. OBJECTIVE: This study aims to optimize the extraction of polyphenols and antioxidant compounds from blueberry pomace by solid-liquid extraction (SLE) and microwave-assisted extraction (MAE). METHODS: A Pareto chart was used to confirm the factor with the highest impact, response surface for analyzing the effect of extraction conditions on total phenol content (TPC) (through Folin-Ciocalteu), total anthocyanin content (TAC) (through differential pH), antioxidant capacity (AC) (through DPPH assay) and the Box-Behnken matrix to determine the optimal conditions for marc extraction with each method. RESULTS: Ethanol concentration is an impact factor for both methods, as well as irradiation method, radiation power for MAE and temperature for SLE. Regarding SLE and MAE extraction, under optimal conditions, a TCP content of 335.95 and 426.19 (mg GAE/100 g), TAC 272.69 and 389.64 (mg Cyn-3-glu/100 g), and CA 528.96 and 654.11 (mg TE/100 g) was obtained, respectively. CONCLUSIONS: The performance of phenolic compound extraction via MAE method is better than that of SLE.

Influence of Brewer’s Spent Grain Compounds on Glucose Metabolism Enzymes

With a yearly production of about 39 million tons, brewer’s spent grain (BSG) is the most abundant brewing industry byproduct. Because it is rich in fiber and protein, it is commonly used as cattle feed but could also be used within the human diet. Additionally, it contains many bioactive substances such as hydroxycinnamic acids that are known to be antioxidants and potent inhibitors of enzymes of glucose metabolism. Therefore, our study aim was to prepare different extracts—A1-A7 (solid-liquid extraction with 60% acetone); HE1-HE6 (alkaline hydrolysis followed by ethyl acetate extraction) and HA1-HA3 (60% acetone extraction of alkaline residue)—from various BSGs which were characterized for their total phenolic (TPC) and total flavonoid (TFC) contents, before conducting in vitro studies on their effects on the glucose metabolism enzymes α-amylase, α-glucosidase, dipeptidyl peptidase IV (DPP IV), and glycogen phosphorylase α (GPα). Depending on the extraction procedures, TPCs ranged from 20–350 µg gallic acid equivalents/mg extract and TFCs were as high as 94 µg catechin equivalents/mg extract. Strong inhibition of glucose metabolism enzymes was also observed: the IC50 values for α-glucosidase inhibition ranged from 67.4 ± 8.1 µg/mL to 268.1 ± 29.4 µg/mL, for DPP IV inhibition they ranged from 290.6 ± 97.4 to 778.4 ± 95.5 µg/mL and for GPα enzyme inhibition from 12.6 ± 1.1 to 261 ± 6 µg/mL. However, the extracts did not strongly inhibit α-amylase. In general, the A extracts from solid-liquid extraction with 60% acetone showed stronger inhibitory potential towards a-glucosidase and GPα than other extracts whereby no correlation with TPC or TFC were observed. Additionally, DPP IV was mainly inhibited by HE extracts but the effect was not of biological relevance. Our results show that BSG is a potent source of α-glucosidase and GPα inhibitors, but further research is needed to identify these bioactive compounds within BSG extracts focusing on extracts from solid-liquid extraction with 60% acetone.

In situ solid-liquid extraction enhances recovery of taxadiene from engineered S. cerevisiae cell factories

A novel in situ solid phase adsorption strategy was investigated for enhanced recovery of taxadiene, a precursor to the blockbuster anticancer drug, paclitaxel, from engineered Saccharomyces cerevisiae. A synthetic adsorbent resin (HP-20) was employed to capture taxadiene across a range of cultivation scales. Cultivations from 12 % (w/v) resin concentration resulted in bead fragmentation which were found to be detrimental to cellular growth. After cultivation, the use of acetone for desorption captured intracellular and secreted taxadiene, achieving an integration of the bioprocess. Implementation of the proposed method at microscale (2 mL) and benchtop bioreactor scale (250 mL) resulted in 1.9-fold and 1.4-fold increments in taxadiene titer, respectively, compared to the extraction method using a dodecane overlay. Taxadiene was found to be distributed between resin beads and biomass in a ratio of 50 %. Finally, a maximum taxadiene titer of 76 ± 19 mg/L was achieved in the benchtop bioreactor cultivations.

Valorization of Bilberry (Vaccinium myrtillus L.) Pomace by Enzyme-Assisted Extraction: Process Optimization and Comparison with Conventional Solid-Liquid Extraction

Bilberry (Vaccinium myrtillus L.) pomace contains a significant amount of polyphenols and can serve as a basis for food additives, nutraceuticals, and functional foods. Although various techniques can be employed to recover bioactive fractions from berry pomaces, data on enzyme-assisted extraction (EAE) of bilberry pomace are rather scarce. This study aimed to optimize critical EAE parameters using Viscozyme L to obtain a high-yield extract with enhanced antioxidant capacity. Central composite design and response surface methodology evaluating the effect of four independent variables, namely, pH, temperature, extraction time, and enzyme concentration on three responses, were employed to define optimal EAE conditions. Under the optimal conditions (pH: 4.5, temperature 46 °C, 1 h of extraction, and 2 active units (AU) of Viscozyme L/g of pomace), EAE yielded 56.15 g/ 100 g DW of the water-soluble fraction. Comparison with conventional maceration indicated that EAE, besides the yield, significantly increased the in vitro antioxidant capacity measured by the total phenolic content, ABTS, ORAC, and CUPRAC assays. Moreover, an increase was observed for the measured mono- and disaccharide as well as anthocyanin content. Overall, this study demonstrates the improved efficiency of EAE over conventional solid–liquid extraction to recover fractions with a higher yield and enhanced functional properties in a fast and sustainable manner.