Microwave-assisted extraction of phenolic compounds from grape seed

A Novel Liquid Chromatographic Time-of-Flight Tandem Mass Spectrometric Method for the Determination of Secondary Metabolites in Functional Flours Produced from Grape Seed and Olive Stone Waste

Agricultural by-products like grape pomace and olive stones are rich in bioactive compounds and can be processed into grape seed and olive stone flours.The phenolic composition of such flours still remains underexplored. This study introduces a liquid chromatographic time-of-flight tandem mass spectrometric method (LC-QTOF-MS/MS) to assess the phenolic profiles of functional flours from different origins and evaluate their potential use within the frame of a circular economy. Grape seed and olive stone flours from Lemnos and commercial sources were analyzed employing target, suspect, and non-target screening. Target screening resulted in the determination of 23 phenolic compounds. Suspect screening revealed phenolic diversity in flours produced in Lemnos island. Non-target screening resulted in the detection of 1042 and 1620 mass features in grape seed and olive stone flours, respectively. Principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) successfully differentiated samples between commercially available and those produced in Lemnos. These results underscore the phenolic richness of grape seed and olive stone flours, supporting their use as functional ingredients and reinforcing sustainability and circular economy principles in the agri-food sector.

Impact of Thermal, High-Pressure, and Pulsed Electric Field Treatments on the Stability and Antioxidant Activity of Phenolic-Rich Apple Pomace Extracts

Apple pomace, a by-product of apple juice production, is typically discarded as waste. Recent approaches have focused on utilizing apple pomace by extracting beneficial bioactive compounds, such as antioxidant phenolic compounds (PCs). Before these PC-rich extracts can be used in food products, they must undergo food preservation and processing methods. However, the effects of these processes on the composition, stability, and properties of the PC remain insufficiently understood. The present study aimed at investigating the effects of a thermal treatment (TT), a high-pressure thermal treatment (HPTT), and a pulsed electric field treatment (PEF) on the composition and antioxidant activity of PC-rich apple pomace extracts (APEs). Major PCs, including phloridzin, chlorogenic acid, and epicatechin, as well as minor compounds, were identified by liquid chromatography-tandem mass spectrometry (LC-MS/MS) and high-performance thin-layer chromatography (HPTLC). As a stability indicative property, the antioxidant activity was analyzed by a Trolox equivalent antioxidant capacity assay (TEAC), electron paramagnetic resonance spectroscopy, and the Folin-Ciocalteu reagent assay. The results showed that TT at 80 °C increased phloridzin content, likely due to the hydrolysis of bound forms, while higher temperatures and HPTT resulted in a substantial PC conversion. The PEF treatment also caused notable PC conversion, but generally, it had a milder effect compared to TT and HPTT. Hence, low temperatures with and without high pressure and PEF seem to be the most promising treatments for preserving the highest content of major PC in APE. Antioxidant activity varied among the analytical methods, with HPTT showing minor changes despite PC loss compared to the untreated APE. This suggests that other antioxidant compounds in the extracts may contribute to the overall antioxidant activity. This study demonstrates that apple pomace contains valuable PC, highlighting its potential as a health-promoting food additive and the impact of conventional preservation and processing methods on PC stability.

Direct microwave treatment enhances antioxidant and antibacterial properties of the seed extracts of Kékfrankos grapes

The Kékfrankos is the most frequently cultivated wine grape in Hungary, with a significant national and regional impact, resulting in considerable amounts of byproducts (e.g. pomace, seeds). To the best of our knowledge no research has been conducted on the antioxidant and antibacterial properties of its seed extracts (GSE). A novel apporach of applying direct microwave treatment on grape seeds was implemented for the first time to enhance antioxidant and antimicrobial properties of GSE. Antioxidant properties were assayed using the DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (Ferric Reducing Antioxidant Power) and TPC (Folin-Ciocâlteu's Total Polyphenol Content) methods. Profile and content of polyphenols was studied using high-performance liquid chromatography/tandem mass spectrometry and matrix-assisted laser desorption/ionization mass spectrometry. Antibacterial properties were evaluated using Gram-positive Staphylococcus aureus (SA), methicillin-resistant Staphylococcus aureus (ST239) (MRSA) and Gram-negative Escherichia coli (EC) bacteria strains. Results proved that the mild direct microwave treatment of grape seeds significantly increased total polyphenol, (+)-catechin, (-)-epicatechin as well as antioxidant capacity levels by 20-30 % compared to untreated samples and resulted the best antibacterial properties based on bacterial growth curves (SA and MRSA: 0.015625 mg/mL, EC: 0.25 mg/mL). Results justify the importance of further pharmacological investigations on Kékfrankos grape seed extracts and that the direct microwave treatment of grape seeds is an innovative approach for the fast and cost efficient improvement of the antibacterial properties of grape seed extracts.

Evaluation of the Phytochemistry-Therapeutic Activity Relationship for Grape Seeds Oil

Seeds' abundant biologically active compounds make them a suitable primary platform for the production of natural extracts, innovative foods, medicines, and cosmetics. High levels of industrial and agricultural residues and byproducts are generated during the processing of grapes, although some parts can also be repurposed. This paper examines the phytochemical composition, manufacturing processes, and health-improving attributes of many varieties of grape oil derived using various extraction methods. Since the results are influenced by a range of factors, they are expressed differently among studies, and the researchers employ a variety of measuring units, making it difficult to convey the results. The primary topics covered in most papers are grape seed oil's lipophilic fatty acids, tocopherols, and phytosterols. In addition, new methods for extracting grape seed oil should therefore be designed; these methods must be affordable, energy-efficient, and environmentally friendly in order to increase the oil's quality by extracting bioactive components and thereby increasing its biological activity in order to become part of the overall management of multiple diseases.

Optimization of Microwave-Assisted Extraction and Matrix Solid-Phase Dispersion for the Extraction of Polyphenolic Compounds from Grape Skin

Polyphenols are organic compounds that can be found in food, especially in fruits, vegetables, and their products. It was shown that their presence significantly affects the properties of food products and that the consumption of food rich in phenolic compounds has a beneficial effect on human health. The subjects of this research were polyphenols: anthocyanins, flavonols, and flavan-3-ols in the skin of grapevine variety Regent. Polyphenols from grape skins were extracted via microwave-assisted extraction (MAE) and matrix solid-phase dispersion (MSPD) as unconventional and green techniques. Therefore, the main aim of this work was to optimize the conditions for the extraction of polyphenolic compounds from grape skin using MAE and MSPD. The extracts were analyzed using high-performance liquid chromatography with a diode array detector and fluorescence detector. Analyses showed that MAE was a very effective method for extracting polyphenolic compounds from grape skin with 10 mL of 60% ethanol for 5 min at 40 °C. The best results for the MSPD extraction of polyphenolic compounds from grape skin were obtained with phenyl as an MSPD sorbent with 10 mL of acetonitrile:water 50:50 v/v as an elution solvent. This scientific research can be used for the better use of grapes as a basis for obtaining flavonoids for commercial purposes.

Optimization of Total Phenol and Tannin Content and Biological Activity of Dittrichia graveolens (L.) GREUTER

Background:

Dittrichia graveolens (L.) is a strongly aromatic plant distributed in Mediterranean regions. This research concerns the optimization of the Total Phenolic Content (TPC) and the Total Tannin Content (TTC) of Dittrichia graveolens (L.) extracts using Response Surface Methodology for Ultrasound Assisted Extraction (UAE) and Microwave Assisted Extraction (MAE). Central Composite Design (CCD) was used to evaluate the effect of the solvent concentration and the extraction time, in different methods on TTC and TPC. The antioxidant activities and antibacterial activities were evaluated.

Methods:

The plant extracts were prepared using maceration, microwave and ultrasound assisted extraction. TPC and TTC were measured using Folin-Ciocalteu method. The antioxidant activities were studied using DPPH reagent and disc diffusion method was used to study the antibacterial activities.

Results:

This study showed the optimum condition for UAE was 49.96% methanol concentration and 11.2 min sonication, while for MAE was 55.44% methanol concentration and 2.26 min microwave extraction. It also indicated that MAE was the most effective method in comparison to UAE and maceration. The antioxidant activities of MAE extract (IC50=7.7mg/mL) were more than UAE extract (IC50=21.5mg/mL) and maceration (IC50=32.3mg/mL).

Conclusion:

As a conclusion, it was indicated that MAE was the most effective method. The higher total phenolic content caused higher antioxidant activities as MAE extract had the highest antioxidant activities. The antibacterial test showed the great potential of this plant as an antibacterial compound resource against different bacteria.

Valorisation of black carrot pomace: microwave assisted extraction of bioactive phytoceuticals and antioxidant activity using Box-Behnken design

The present study compares three methods viz. microwave assisted extraction (MAE), ultrasonic-assisted extraction (UAE) and conventional solvent extraction (CSE) for extraction of phenolic compounds from black carrot pomace (BCP). BCP is the major by-product generated during processing and poses big disposal problem. Box-Behnken design using response surface methodology was employed to investigate and optimize the MAE of phenolics, antioxidant activity and colour density from BCP. The conditions for maximum recovery of polyphenolics were: microwave power (348.07 W), extraction time (9.8 min), solvent-solid ratio (19.3 mL/g) and ethanol concentration (19.8%). Under these conditions, the extract contained total phenolic content of 264.9 ± 10.02 mg gallic acid equivalents (GAE)/100 mL, antioxidant capacity (AOC) of 13.14 ± 1.05 µmol Trolox equivalents (TE)/mL and colour density of 68.63 ± 5.40 units. The total anthocyanin content at optimized condition was 753.40 ± 31.6 mg/L with low % polymeric colour of 7.40 ± 0.42. At optimized conditions, MAE yielded higher colour density (68.63 ± 5.40), polyphenolic content (264.9 ± 10.025 mg GAE/100 mL) and AOC (13.14 ± 1.05 µmol TE/mL) in a short time as compared to UAE and CSE. Overall results clearly indicate that MAE is the best suited method for extraction in comparison to UAE and CSE. The phenolic rich extract can be used as an effective functional ingredient in foods.

Current technologies and new insights for the recovery of high valuable compounds from fruits by-products

The recovery of high valuable compounds from food waste is becoming a tighten issue in food processing. The large amount of non-edible residues produced by food industries causes pollution, difficulties in the management, and economic loss. The waste produced during the transformation of fruits includes a huge amount of materials such as peels, seeds, and bagasse, whose disposal usually represents a problem. Research over the past 20 years revealed that many food wastes could serve as a source of potentially valuable bioactive compounds, such as antioxidants and vitamins with increasing scientific interest thanks to their beneficial effects on human health. The challenge for the recovery of these compounds is to find the most appropriate and environment friendly extraction technique able to achieve the maximum extraction yield without compromising the stability of the extracted products. Based on this scenario, the aim of the current review is twofold. The first is to give a brief overview of the most important bioactive compounds occurring in fruit wastes. The second is to describe the pro and cons of the most up-to-dated innovative and environment friendly extraction technologies that can be an alternative to the classical solvent extraction procedures for the recovery of valuable compounds from fruit processing. Furthermore, a final section will take into account published findings on the combination of some of these technologies to increase the extracts yields of bioactives.

Microwave-assisted autohydrolysis of Prunus mume stone for extraction of polysaccharides and phenolic compounds

Stone of Prunus mume (P. mume) is a by-product of pickled P. mume industry. Stones of native and pickled P. mume, mainly composed of holocellulose (83.8 +/- 1.8% and 65.1 +/- 0.3%, respectively) and acid-insoluble lignin (25.3 +/- 2.2% and 30.6 +/- 0.9%, respectively), were autohydrolyzed by microwave heating to extract polysaccharides and phenolic compounds. By heating at 200 to 230 degrees C, 48.0% to 60.8% of polysaccharide and 84.1% to 97.9% of phenolic compound were extracted in water along with partial degradation of hemicelluloses and lignin. The extracted liquors showed antioxidant activity against hydroxyl radical and DPPH radical originated from phenolic compounds. The pickled P. mume stone showed higher autohydrolyzability and microwave absorption capacity than the native stone due to absorbed salts and acids during pickling in fruit juice of P. mume with external addition of sodium chloride. Pickling process in salty and weak acidic juice seemed to be a kind of pretreatment for softening the stones prior to autohydrolysis induced by microwave heating.

Microwave assisted extraction of phenolic compounds from four different spices

Spices and herbs are known not only for their taste, aroma and flavour, but also for their medical properties and value. Both spices and herbs have been used for centuries in traditional medical systems to cure various kinds of illnesses such as common cold, diabetes, cough and cancers. The aim of this work was the comparison between two different extractive techniques in order to get qualitative and quantitative data regarding bioactive compounds of four different spices (Cinnamomum zeylanicum, Coriandrum sativum, Cuminum cyminum, Crocus sativus). The plants were extracted employing ultrasonication and microwave-assisted extractions. The efficiency of extraction of bioactive compounds obtained with the microwave extraction process was in general about four times higher than that resulting from sonication extraction. The various extracts obtained were analyzed for their antioxidant activity using ABTS, DPPH and FRAP assays and for their total polyphenolic content. It can be concluded that microwave-assisted extractions provide significant advantages in terms of extraction efficiency and time savings.

Biological activities of polyphenols from grapes

The dietary consumption of grape and its products is associated with a lower incidence of degenerative diseases such as cardiovascular disease and certain types of cancers. Most recent interest has focused on the bioactive phenolic compounds in grape. Anthocyanins, flavanols, flavonols and resveratrol are the most important grape polyphenols because they possess many biological activities, such as antioxidant, cardioprotective, anticancer, anti-inflammation, antiaging and antimicrobial properties. This review summarizes current knowledge on the bioactivities of grape phenolics. The extraction, isolation and identification methods of polyphenols from grape as well as their bioavailability and potential toxicity also are included.

Proanthocyanidins: target compounds as antibacterial agents

Grape seeds accumulate in huge quantities as byproduct during wine production and are therefore a cheap source for pharmacologically active agents. However, studies prove poor antibacterial activity, and results of analyses are sometimes contradictory. The aim of this study was, thus, to determine the antibacterial activity of grape seed extracts with special focus on the chromatographic characterization of active fractions. In the course of these investigations, extraction protocols were optimized so that microwave-assisted extraction (MAE) guaranteed highest preconcentration efficiency. Proanthocyanidins, monomeric flavonoid aglycones, as well as some of their glycosides could be identified within yielded extracts via high-performance liquid chromatography-mass spectrometry (HPLC-MS). By that means the coherence number of possible isomers of procyanidins was approximated by a newly developed equation. As far as antibacterial activity determined via screening tests is concerned, the extracts generally have been found to be positively responsive toward 10 different gram-positive and gram-negative bacteria strains. After fractionation of the raw extracts, proanthocyanidins P2, P3, P4 and gallate esters P2G and P3G (P = proanthocyanidin consisting of catechin and epicatechin units, n = oligomerization degree, G = gallate ester) were determined as active antibacterial agents toward 10 different pathogens. Only moderate activity was found for monomeric flavonoid fractions.

Preparation of botanical samples for biomedical research

Plants are chemical storehouses, a fact which has driven countless multidisciplinary quests for bioactive compounds. As the very first step of botanical research, the whole desire is to find "hit" plants with specific bioactivities. It is logical to use some strategies that can maximize the chances of finding these "hits" with limited time and resources. In addition to selecting the right plants for screening, how the plant extracts are prepared can also influence the bioactivity screening outcomes. An extract from the same plant material can be quite different in chemical composition having different preparations. Because of the complex mixture nature of plant extracts, it is possible artifact activities may be observed. Thus confirmatory activity tests are often necessary to warrant the next laborious isolation step. A bioassay directed isolation approach may be the most efficient in identifying the bioactive compounds because of the narrowed focus at each isolation step, but a phytochemistry isolation approach is appropriate to characterize a purified bioactive extract. In fact, these two approaches can be taken intermittently whenever efficiency can be improved. Finally, use of the identified active compounds is now broader. In addition to determining a lead compound to continue a drug development path, there is an increasing interest in support for the use of botanical extracts as botanical drugs. Instead of dropping the extract after extracting the lead compound, the natural analogues representing the purified extract now have a chance to become leading compounds in the pursuit of novel therapies for metabolic syndrome and other diseases.

Quality assessment and quantitative analysis of flavonoids from tea samples of different origins by HPLC-DAD-ESI-MS

Components of green tea ( Camellia sinensis) have been of considerable interest in recent years because of their potential utility as pharmaceutical agents, particularly for their antioxidant and anticarcinogenic activity. Responding to the increasing scientific validation of numerous health benefits of tea, a comprehensive approach was adopted to carry out analysis for the quality assessment of flavonoids in tea samples of different origins. For this purpose, extraction, separation, and mass spectrometric parameters were optimized. Extraction methods evaluated include reflux extraction, a modified accelerated solvent extraction (ASE), namely, Aquasolv extraction, and microwave-assisted extraction (MAE) using different percentages of solvents. Separation was performed by a specifically developed reversed phase high-performance liquid chromatography (RP-HPLC) method using different C18 and C8 stationary phases. Optimization of extraction techniques clearly proved the performance of MAE, which delivered highest yields in a very short time. Additionally, the comparison with Aquasolv extraction provided new insights, as variations in quantified amounts of target compounds between the extracts could be explained on the basis of thermal degradation and epimerization phenomena. Especially the epimerization phenomenon for catechin/epicatechin oligomers, that is, of procyanidins P 2 and P 3, was observed for the first time. Finally, an optimized extraction and separation system was used for qualitative and quantitative investigations of compounds from different green tea samples from Ceylon (cultivated under biologically controlled conditions), Japan, India, and China as well as from one black tea sample from India.

Extraction of polyphenols from white distilled grape pomace: optimization and modelling

Both ethanolic and aqueous extraction were carried out in a laboratory-scale vertical extractor to obtain polyphenols from distilled grape pomace of Vitis vinifera var. "Albariño". An experimental design was performed to analyse the effects of flow (2 ml/min and 4 ml/min) and temperature (40 degrees C and 50 degrees C). Yields of polyphenolics from aqueous extraction were much higher (up to 30-fold) than those of ethanolic extraction, in contrast with previous results obtained by us from batch extraction of different grape varieties. Polyphenols extraction was modelled by application of second Fick's law to spherical particles of 0.5 mm diameter, so obtaining the effective diffusion coefficient as parameter. The mass transfer coefficients were also estimated, giving as result that the external mass transfer resistance was negligible. Correlation coefficients ranged 0.989-0.9999. Effective diffusivity values in water extraction assays were between 0.6x10(-11) m(2)/s and 2.1x10(-11) m(2)/s. Using ethanol as solvent, the effective diffusivity was lower, between 0.1x10(-11) m(2)/s and 0.76x10(-11) m(2)/s.

Microwave assisted extraction of soy isoflavones

A fast and reliable analytical method using microwave assisted extraction has been developed. Several extraction solvents (methanol (MeOH) and ethanol (EtOH), 30-70% in water and water), temperatures (50-150 degrees C), extraction solvent volume, as well as the sample size (1.0-0.1g) and extraction time (5-30 min) were studied for the optimization of the extraction protocol. The optimized extraction conditions for quantitative recoveries were: 0.5 g of sample, 50 degrees C, 20 min and 50% ethanol as extracting solvent. No degradation of the isoflavones was observed using the developed extraction protocol and a high reproducibility was achieved (>95%).

Determination of capsaicinoids in peppers by microwave-assisted extraction-high-performance liquid chromatography with fluorescence detection

A new method has been developed for the extraction of capsaicinoids (nordihydrocapsaicin, capsaicin, dihydrocapsaicin, homocapsaicin and homodihydrocapsaicin) in peppers employing microwave-assisted extraction. The parameters studied are: extraction solvent (methanol, ethanol, acetone, ethyl acetate and water), temperature (50-200 degrees C), sample quantity (0.1-1 g), volume of solvent (15-50 mL) and the extraction time (5-20 min). The results found for the optimum conditions are: 125 degrees C as extraction temperature, 25 mL of solvent, 0.5 g of freshly triturated peppers and extraction for 5 min, employing 100% ethanol as solvent. The capsaicinoids obtained were stable under the optimised extraction conditions. The resulting method presents a high degree of reproducibility (R.S.D.<6%).