Extraction Of Total Phenolic Compounds Research Articles

Ultrasound assisted intensified enzymatic extraction of total phenolic compounds from pomegranate peels

Pomegranate peels contain a considerable amount of bioactive chemicals, such as phenolic compounds like gallic acid and ellagic acid. The current study aims to optimize the extraction of total phenolic content (TPC) and its antioxidant capacity from a Pomegranate peel using various approaches involving enzyme and ultrasound, also focusing on process intensification using combination. The optimal parameters for ultrasound treatment were treatment time of 25 min, 130 W power, 50 % duty cycle, and a liquid–solid ratio of 50:1 at a fixed 22kHz frequency, resulting in maximum TPC (21.521 mg GAE/ml) and antioxidant capacity (17.962 mg GAE/ml). Similarly, enzymatic treatment was optimized resulting in best conditions of a time of 55 min, 50 °C temperature, pH 5, and a 2 % enzyme concentration. Ultrasound-assisted enzymatic extraction (UAEE) experiments revealed that combining 25 min of ultrasonic treatment with 25 min of enzymatic treatment yielded the highest TPC (30.608 mg GAE/ml) and antioxidant capacity (27.703 mg GAE/ml). It was clearly demonstrated that UAEE outperformed EAE and UAE in terms of Total Phenolic Compound extraction and antioxidant capacity, with the order of efficiency being UAEE > EAE > UAE.

Extraction of phenolic compounds from spent coffee ground using natural deep eutectic solvents: New modeling approach

AbstractThe extraction of bioactive compounds from food wastes or by‐products with natural deep eutectic solvents (NADES) could be an attractive alternative to traditional hydroalcoholic extraction but needs to be optimized taking advantage of modeling. This work aims to propose, develop, and discuss a new model for the extraction of phenolic compounds from spent coffee grounds (SCGs) using NADES to overcome some gaps related to the kinetic extraction models and the surface response methodology. The model presented is based on the same assumption as the kinetic model, but improving it to be able to predict phenolic extraction changing different process parameters (e.g., water content, time of extraction, temperature, etc.) using betaine: triethylene glycol (molar ratio 1:2). The model was validated on the extraction of total phenolic compounds from SCG as a function of water content of NADES ranging from 30 to 60% v/v. There was good agreement between experimental and simulated data and even, in some cases, better than with the second‐order kinetic models. In addition, the new model needs fewer parameters to be regressed concerning the specific case investigated in this work. This model and methodology can be the basis for further modeling applicable to other bioactives, and/or other NADES and feedstocks.Practical ApplicationsNatural deep eutectic solvents (NADES) can be a potential sustainable solvent for the valorization of food by‐products as they can be used to extract bioactive compounds with high added value. This extraction process needs to be optimized depending on several factors like water content in NADES solution, solids ratio, extraction time, and temperature. The model validated in this work on spent coffee ground (SCG) could be used for this purpose, improving the gaps related to the kinetic extraction models and the surface response methodology (RSM). The new model enables predicting the behavior of the process as a function of the parameters previously mentioned and reduces the number of experimental trials required compared with RSM. In particular, the new model was validated on the variation of water content in NADES solution. Certainly, this model will need to be further validated, but, once further studies are conducted, this model could be used for scale‐up calculation and design optimization of the industrial process.

Kinetic modeling of valuable phenolic compounds extraction from strawberry and apple agro‐industrial by‐products

AbstractExtracting valuable compounds from waste plant tissues is a challenging process. To better understand this process, kinetic modeling was used to study the extraction of phenolic compounds from the waste tissues of industrial strawberry (RF) and apple (GS) processing using green solvents. The experimental design variables included type of solvent (W: water, EtOH: ethanol 80%), solid–liquid ratio (1:20, 1:30, 1:40), and temperature (20, 70°C). The model of Peleg (MI) and an empirical model (MII) were applied to determine the kinetic constants for total phenolic compounds (TPC) and antioxidant capacity (AC). The phenolic compound profile was determined at each experimental assay. The extraction variables affected (p < 0.001) TPC and AC of RF and GS extracts. Using EtOH increased TPC extraction yields from both tissues (up to 62% for RF). The highest AC was determined in EtOH extracts at 20°C (119 and 25 μmol TE/g for RF and GS, respectively). Temperature, extraction ratio, and solvent type significantly affected the kinetic constants of both models. The study identified nine phenolic compounds from both waste tissues, with Agrimoniin being the main compound in RF (0.49 g/kg) and quercetin pentoxide being the main compound in GS (0.23 g/kg). There was no significant increase in TPC and AC of the extracts after 90 min at 20°C and 60 min at 70°C. The kinetic modeling of phenolic compound extraction from strawberry and apple agro‐industrial by‐products using green solvents enabled the determination of the best extraction conditions, promoting the use of these waste tissues by obtaining bioactive compounds with antioxidant potential.Practical ApplicationsThis study provides valuable insight into the effective use of green solvents in extracting bioactive compounds, thereby promoting sustainable practices and reducing waste in the industrial processing of strawberries and apples. The kinetic modeling approach for recovering phenolic compounds from strawberry and apple agro‐industrial by‐products improves our comprehension of the influence of the extraction process variables on the phenolic compound profile and antioxidant capacity of these tissues. These findings highlight the potential of these waste tissues as an alternative source of bioactive compounds. By standardizing the extraction process and optimizing the utilization of agro‐industrial by‐products, the food industry can effectively reduce the environmental impact of these waste tissues and promote sustainable operations. Additionally, using green solvents aligns with the increasing demand for environmentally friendly practices, making it easier to turn strawberry and apple agro‐industrial processes into circular processes by eco‐friendly valorization of these biowastes.

Kinetic modeling of phenolic compounds extraction from nutshells: influence of particle size, temperature and solvent ratio

AbstractThis paper studies the effects of particle size, temperature and ethanol–water solvent ratio on the extraction of total phenolic compounds (TPC) from peanut, coconut, and macadamia nutshells. Using an I-optimal design, the maximum TPC extraction obtained from the shells ranged from 63.5 ± 1.6 to 76.2 ± 3.1 mg gallic acid equivalent (GAE) per 100 g dry weight (dw) of nutshell. Next, a response surface model (RSM) was developed to describe the relationship between the process parameters and the extracted TPC concentration, in order to predict the optimal extraction conditions. For all of the examined biomasses, the optimal conditions for extraction were predicted at a particle size of 1 mm, temperature of 75 °C and ethanol/water mixture of 54, 53 and 65% ethanol, for peanut, coconut and macadamia nutshells respectively. Particle size seems to be the most important parameter, while temperature appears to be of lesser importance. Besides, the extraction kinetics were assessed by fitting kinetic models on the experimental data. The combined second-order diffusional model provided the best goodness of fit. This model revealed that, at the boundary layer, the effect of washing mechanism of extraction is more important than extraction due to diffusion kinetics. This study provides an understanding of the mass transfer mechanism involved in the TPC extraction process from nutshells, which yields valuable insights that could facilitate the industrial biorefinery of nutshells. Graphical Abstract

Optimization of phenolic compounds extraction from olive mill wastewater using response surface methodology.

Large amounts of pomace are produced during the extraction of olive oil. This is because only 21% of an olive's weight is made up of oil, while 79% includes water, bark and pulp. This project extracted total phenolic compounds (TPCs) from olive mill wastewater as efficiently as possible. The TPCs were analyzed and the total antioxidant activity (TAA) was evaluated by spectrophotometry. Data were evaluated using the response surface method (RSM). The largest TAA and TPC were discovered in extracting using 80% ethanol at 25 °C, and 2.5 bar with pH = 4. The highest amount of TPCs was 11.614 mg of gallic acid per 100 mL, and a value of 71.06% was reported for TAA. The results of the quadratic model showed that R2 is equal to 0.937, because it has a larger coefficient and the pH factor had the least effect. The temperature factor had the greatest impact on the extraction of TPC and TAA, and the mutual temperature and pH impacts affected the extraction positively. As a result, it can be concluded that the RSM was a useful tool for assessing the ideal circumstances for phenolic component extraction.

Optimization of the extraction of phenolic compounds from the leaves of yerba mate (Ilex paraguariensis) through high hydrostatic pressure system using mixture design with process variables.

In this study, a mixture design with process variables was used to optimize the extraction of total phenolic compounds (TPC) from yerba mate leaves through high hydrostatic pressure extraction. The studied variables were pressure (50, 100, and 150 MPa), extraction time (10, 20, and 30 min), and solvent (water, glycerin, and 50% v/v water/50% v/v glycerin). The multiple linear regression model presented an excellent fit (R2 adjusted of 0.9792) and demonstrated the major influence of glycerin content on the water/glycerin mixture solvent for TPC extraction. Optimal process conditions obtained were 69% v/v water, 31% v/v glycerin, 50 MPa pressure, and 10 mintime. PRACTICAL APPLICATION: The paper describes a novel extraction method to obtain phenolic compounds from yerba mate (compounds that can replace synthesized antioxidants in the food industry) using high hydrostatic pressure and environmentally friendly solvents. The extraction process was studied to optimize its performance, obtaining more phenolic compounds from the same amount of yerbamate.

Subcritical water extraction of total phenolic compounds from Piper betle L. leaves: effect of process conditions and characterization

Subcritical water extraction of total phenolic compounds from Piper betle L. leaves: effect of process conditions and characterization

Green and innovative extraction of polyphenols from Rhamnus alaternus using natural deep eutectic solvents and evaluation of their bioactivities

Phenolic compounds, naturally present in plants, are particularly relevant as nutraceutics for their antioxidant activities. Here, choline chloride-based natural deep eutectic solvents (NaDESs) were used for efficient extraction of total phenolic compounds (TPC) from leaves, pods and roots of Rhamnus alaternus plant. In each extract, the polyphenols content and their antioxidant activities were evaluated. More, their antibacterial activity was carried out against Gram-positive and Gram-negative bacteria. The investigated extracts presented antioxidant and antimicrobial activities. The leaves, pods and roots extracts obtained using the choline chloride-glycerol (ChCl-Gly) mixture exhibited a high value of TPC comprised within 437.7 and 317.0 mg GAE/100 g d.w. and showed the best antioxidant properties with ABTS radical scavenging capacity (IC50: from 44.55 to 53.56 µg/mL), DPPH assay (IC50: from 26.36 to 118.23 µg/mL), reducing activity (EC50: from 77.53 to 85.05 µg/mL) and iron chelation activity (EC50: from 91.73 to 108.7 µg/mL). In contrast, choline chloride-urea (ChCl-Ur) extracts showed a low antioxidant capacity. Lastly, the best bioactive extracts were characterized using HPLC-MS/MS to determine their bioactive compounds. The present study suggests that the DES-based method developed was selective, efficient and sustainable for extraction of polyphenols.

Concurrent Optimization of Ultrasonic-Assisted Extraction of Total Phenolic Compounds and In Vitro Anticancer and Antioxidant Potential of Pulicaria schimperi (Aerial Parts) Using Response Surface Methodology

This study aimed to maximize the dependent variables [total phenolic content (TPC), antioxidant (DPPH and ABTS), and anticancer activities (against HepG2 and MCF-7 cells)] from P. schimperi aerial parts by optimizing three independent variables (extraction temperature, extraction time, and liquid-to-solid ratio) of ultrasound-assisted extraction (UAE) using the Box–Behnken design (BBD) of response surface methodology (RSM). For each of the dependent variables, the projected quadratic models were found to be very significant (p < 0.001). The extraction temperature and extraction time had a significant impact on the TPC extraction, antioxidant, and anticancer properties (p < 0.05). The best conditions were identified as an extraction temperature of 54.4 °C, extraction time of 48 min, and liquid-to-solid ratios of 20.72 mL/g for the simultaneous extraction of the TPC, antioxidant, and anticancer properties of P. schimperi. The experimental results and the expected values agreed under these circumstances. Regarding the high extraction effectiveness and antioxidant and anticancer effects at comparably low extraction temperature and duration, UAE demonstrated considerable benefits over conventional solvent extraction (CSE). This improved UAE approach has shown a potential use for effective polyphenolic antioxidant extraction from P. schimperi aerial parts in the nutraceutical sectors.

Kinetic modelling of total phenolic compounds from Ilex paraguariensis (St. Hil.) leaves: Conventional and ultrasound assisted extraction

In this paper, we compared ultrasound-assisted extraction (UAE) and conventional extraction by agitation (AE) for total phenolic compounds (TPC) extraction from yerba mate leaves (Ilex paraguariensis St. Hil). Water and 50% aqueous ethanol solution were used as solvent and the effect of solvent-to-solid ratio, particle size, stirring speed (AE) and ultrasound power amplitude (UAE) was examined. Two kinetic models (i.e. Peleg model and swelling / diffusion model) have been introduced to describe the kinetics of TPC extraction. The experimental data were adequately fitted by swelling/diffusion model (R2>0.98; EP<10%; RMSE<0.24) that considers two mechanisms coupled at different rates. The initial extraction rate increased at a higher volume of solvent (10 ml/g), smaller particle size (0.297 mm) higher ultrasound power amplitude (100%) and the use of 50% aqueous ethanol solution. Maximum equilibrium TPC concentration was observed with the synergic effect of 50% aqueous ethanol solution and the higher power amplitude (15,0 g GAE/100 g dm). This work would provide more information on the extraction mechanisms that occur in the microstructure of yerba mate leaves for the industrial production of TPC.

Ultrasound-Assisted Extraction of Total Phenolic Compounds and Antioxidant Activity Evaluation from Oregano (Origanum vulgare ssp. hirtum) Using Response Surface Methodology and Identification of Specific Phenolic Compounds with HPLC-PDA and Q-TOF-MS/MS.

Oregano is native to the Mediterranean region and it has been reported to contain several phenolic compounds particularly flavonoids that have been related with multiple bioactivities towards certain diseases. Oregano is cultivated in the island of Lemnos where the climate promotes its growth and thus it could be further used in promoting local economy. The aim of the present study was to establish a methodology for the extraction of total phenolic content along with the antioxidant capacity of oregano by using response surface methodology. A Box-Behnken design was applied to optimize the extraction conditions with regard to the extraction time, temperature, and solvent mixture with the use of ultrasound-assisted extraction. For the optimized extracts, identification of the most abundant flavonoids (luteolin, kaempferol, and apigenin) was performed with an analytical HPLC-PDA and UPLC-Q-TOF MS methodology. The predicted optimal conditions of the statistical model were identified, and the predicted values confirmed. The linear factors evaluated, temperature, time, and ethanol concentration, all showed significant effect (p < 0.05), and the regression coefficient (R2) presented a good correlation between predicted and experimental data. Actual values under optimum conditions were 362.1 ± 1.8 and 108.6 ± 0.9 mg/g dry oregano with regard to total phenolic content and antioxidant activity based on 2,2-Diphenyl-1-picrylhydrazyl (DPPH) assay, respectively. Additionally, further antioxidant activities by 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid (ABTS) (115.2 ± 1.2 mg/g dry oregano), Ferric Reducing Antioxidant Power (FRAP) (13.7 ± 0.8 mg/g dry oregano), and Cupric Reducing Antioxidant Capacity (CUPRAC) (1.2 ± 0.2 mg/g dry oregano) assays were performed for the optimized extract. The extract acquired under the optimum conditions contain an adequate quantity of phenolic compounds that could be used in the production of functional foods by food enrichment procedure.

Establishment of a Sonotrode Ultrasound-Assisted Extraction of Phenolic Compounds from Apple Pomace

Apple pomace is the main by-product from apple processing in the juice industry and is considered a source of polyphenols with several health bioactivities. Thus, this research focuses on the establishment of the ultrasound-assisted extraction of total phenolic compounds, focusing on phloretin and phloridzin, with high antioxidant activity from apple pomace, using a sonotrode. We used a Box-Behnken design of 15 experiments with 3 independent factors (ethanol (%), time (min) and amplitude (%)). The responses evaluated were the sum of phenolic compounds, phloretin and phloridzin measured by HPLC-MS-ESI-TOF, and antioxidant activity measured by DPPH, ABTS and FRAP. The validity of the model was confirmed by ANOVA. Further, it was carried out using a comparison between different apple pomaces with or without seeds extracted by the optimal conditions. Phloretin and phloridzin accounted for 7 to 32% of the total phenolic compounds in the apple pomaces. Among all the apple pomace analyzed, that of the variety Gala had the highest phenolic content and antioxidant activity. The presence of the cyanogenic compound amygdalin was detected in apple pomaces that contained seeds accompanied with a higher content of phloretin and phloridzin but a lower content of flavan-3-ols.

Chitosan suspension as extractor and encapsulating agent of phenolics from acerola by-product

The polymeric suspension of chitosan (Ch) has been an effective media for the extraction of total phenolic compounds (TPC) from the acerola by-product. It facilitates the subsequent production of nanoparticles loaded with the phenolics (Np-TPC) by ionic gelation. However, neither the effects of Ch concentration on encapsulation efficiency (EE%) of TPC nor which compounds are extracted in its media are known, being it the first objective of this study. The second objective was to analyze the stability of the Np-TPC under accelerated conditions and its release profile at pHs 3.0 and 7.0. The results showed that Ch does not affect the extraction of TPC. However, the EE increased from 35.0 to 48.1 % with the increase of Ch concentration (0.4 to 1.0 %). LC/ESI-QTOF MS analysis showed that phenolic acids and flavonoids are extracted in 0.8 % Ch medium. After encapsulation, microscopy images revealed particle sizes ranging between 110 and 150 nm. Additionally, the presence of phenolics did not change the stability of the particles under accelerated conditions and the actives were fully released into the released medium for 10 h. The Np-TPC suspension appears to be useful for the production of edible antioxidant coatings to preserve fruits/vegetables, with potential application as carrier of other food ingredients.

Optimization of Polyphenols' Recovery from Purple Corn Cobs Assisted by Infrared Technology and Use of Extracted Anthocyanins as a Natural Colorant in Pickled Turnip.

An ecofriendly extraction technology using infrared (IR) irradiation Ired-Irrad® was applied to purple corn cobs to enhance polyphenol recovery for the first time. The IR extraction efficiency was compared to that of the water bath (WB) method. Response surface methodology (RSM) using a central composite design was conducted to determine the effect of the experimental conditions (extraction time and treatment temperature) and their interactions on the total polyphenol and anthocyanin yields. Optimal extraction of total phenolic compounds (37 mg GAE/g DM) and total monomeric anthocyanins (14 mg C3G/g DM) were obtained at 63 °C for 77 min using IR as an extraction technique and water as a solvent. HPLC revealed that the recovery of peonidin 3-O-glucoside and cyanidin 3-O-glucoside was enhanced by 26% and 34%, respectively, when using IR. Finally, purple corn cobs’ spray-dried extract was proven to be an important natural colorant of pickled turnip. It offers great potential for use as a healthy alternative to the carcinogenic rhodamine B synthetic dye, which was banned.

Intensification of total phenolic compounds extraction from Azadirachta indica (Neem) leaves by ultrasound

The current work deals with ultrasound-assisted extraction (UAE) of the total phenolic compounds (TPC) from A. indica (Neem) leaves powder. Various process parameters have been optimized, including solvent screening, solid/solvent ratio, extraction temperature, particle size, power input, duty cycle, and sound wave frequency. The highest TPC yield of 11.87 mg of GA/g of powder was obtained at a time of 14 min, 70% ethanol as solvent, solid to solvent ratio of 1:30, particle size of 0.2–0.3 mm, extraction temperature of 40ºC, power input of 90 W, and duty cycle of 50%. The experimental outcomes obtained from the UAE have been matched with stirred batch and Soxhlet extraction of TPC, which shows that ultrasound, was relatively better than the traditional method. The UAE method has efficiently decreased the extraction time (14 min) and marginally improved the TPC yield from A. indica leaves. Further, Peleg's mathematical model was studied for the extraction kinetics and to calculate the predicted extraction values of the rate constant, initial rate, and equilibrium concentration for all investigational circumstances. The predicted values obtained from Peleg's mathematical model show a good fit with experimental outcomes.

Enhanced ultrasonically assisted extraction of bitter melon (Momordica charantia) leaf phenolic compounds using choline chloride-acetic acid–based natural deep eutectic solvent: an optimization approach and in vitro digestion

Bitter melon (Momordica charantia) is a rich source of phytochemicals including phenolic compounds with diverse health-promoting benefits and potential food industry application due to their antioxidant potential. Bitter melon leaves have been limitedly investigated in comparison to bitter melon fruits. The current work explores the use of green extraction methodology to optimize enhanced extraction of phenolic compounds from bitter melon leaves using ultrasonically assisted extraction and choline chloride-acetic acid (CHAC)–based natural deep eutectic solvent. Extraction using CHAC significantly improved the extraction of total phenolic compounds, total flavonoids, and individual phenolic compounds (including gallic acid, chlorogenic acid, vanillic acid, epicatechin, and quercetin-3-glucoside) in comparison to water, ethanol, and methanol. The effect of molar ratio, water content, temperature, and time on the extraction efficiency of bitter melon leaf phenolic compounds by CHAC was explored and optimized with surface response methodology (central composite design). The optimum condition for the extraction of individual phenolic compounds is a molar ratio of 1:4.35 CHAC with 20.68% water content at 75 °C for 21.23 min. Evaluation of the bioaccessibility of individual phenolic compounds concluded that the most bioaccessible compound was vanillic acid (105.00 ± 2.52%) followed by salicylic acid, chlorogenic acid, syringic acid, gallic acid, epicatechin, and quercetin-3-glucoside.

Ultrasound-Assisted Extraction of Total Phenolic Compounds and Antioxidant Activity in Mushrooms

The consumption of mushrooms has considerably increased in recent years because of their beneficial nutritional properties due to their essential amino acids, proteins, and dietary fiber content. Recent research has shown that they are also rich in polysaccharides and phenolic compounds. These compounds exhibit decisive free radical and ROS scavenging power with potential application to the treatment of neurodegenerative disorders. In addition, they present important properties like antioxidant, antiaging, and immune modulation. In the present research, the optimization for the extraction of total phenolic compounds and the antioxidant activity (DPPH and ABTS), based on ultrasound–assisted techniques has been carried out. Five variables (% MeOH in solvent, extraction temperature, amplitude, cycle, and sample:solvent ratio have been selected; both the total phenolic compounds content as well as the antioxidant activity (DPPH and ABTS)) have been considered as the response variables. The optimal conditions, determined by means of a multiresponse optimization method, were established at 0.2 g of sample extracted with 15.3 mL of solvent (93.6% MeOH) at 60 °C for 5 min and using 16.86% amplitude and 0.71 s−1 cycles. A precision study of the optimized method has been performed with deviations lower than 5%, which proves the repeatability and precision of the extraction method. Finally, the extraction method has been applied to wild and commercial mushrooms from Andalusia and Northern Morocco, which has confirmed its suitability for the extraction of the phenolic compounds from mushroom samples, while ensuring maximum antioxidant activity.

Impact of pretreatments with ethanol and freezing on drying slice papaya: drying performance and kinetic of ultrasound-assisted extraction of phenolics compounds.

Pretreatments of drying can represent an alternative to minimize the negative aspect process on the dry samples. Thus, the influence of ethanol (ET) and freezing (FG) as drying pretreatments was analyzed for slices of papaya. The slices (5 mm) were submitted for drying kinetics (60 °C and 1.5m s-1 ). Drying kinetics experimental data were fitted using Page's model and a diffusive model with boundary condition of types I and III. Also the thermophysical properties (thermal conductivity and specific heat) were determined and finally, the kinetics of ultrasound-assisted (40 kHz and 132 W) extraction of total phenolic compounds (TPCs) were realized. The combined method (ET + FG) was more efficient in reducing the drying time of papaya slices (48%) and the model 2 simulating the boundary condition of the third type (type III) showed the best fit to the experimental data. Effective diffusivity and convective coefficient were higher for ET + FG, where the maximum reduction in water content was 91% compared to fresh slices. The pretreatments did not influence the thermal conductivity, however, they were significant in the specific heat and in the extraction of TPCs, being higher in the time of 180 min. It was confirmed in the results presented that the combined pretreatment ET + FG is the most viable for drying papaya slices. Furthermore, it was found to be the most efficient in minimizing the loss of TPCs. Therefore, this pretreatment has great potential for application in the development of high value-added foods. © 2022 Society of Chemical Industry.

Mango ‘criollo’ by-products as a source of polyphenols with antioxidant capacity. Ultrasound assisted extraction evaluated by response surface methodology and HPLC-ESI-QTOF-MS/MS characterization

Ultrasound assisted extraction (UAE) was evaluated as a green procedure for the recovery of phenolic compounds with antioxidant capacity from underutilized mango 'criollo' (peel, pulp and seed). Magnetic stirred was performed as conventional extraction. Response surface methodology using a three-factor (% ethanol, amplitude and time) central composite design was used to maximize the extraction for total phenolic compounds (TPC), total flavonoids and antioxidant capacity. The operational conditions to maximize extraction were: peel, 46% ethanol/amplitude 60% (36 µm)/6.5 min; pulp, 25% ethanol/amplitude 75% (45 µm)/30 min; seed 49% ethanol/100% (60 µm) amplitude/20 min. The phenolic composition of the optimized extracts was characterized by HPLC-QTOF-MS/MS and 45 compounds were tentatively identified as xanthones (mangiferin), flavonoids (quercetin), ellagic acid, benzophenones (maclurin), gallate derivatives and gallotannins. UAE increased TPC extraction (33%); interestingly mangiferin extraction increased 53% in peel, similarly, ellagic acid increased up to 2.5 and 4.4 times in peel and seed extracts.

Characterization of Unripe Grapes (Vitis vinifera L.) and Its Use to Obtain Antioxidant Phenolic Compounds by Green Extraction

Thinning pruning is a process in modern viticulture to improve product quality when grapes are still in the immature fruit stage. Unripe grapes, which are waste, are mostly consumed locally as verjuices to meet domestic demand. This study aims to optimize a more efficient “green” technique for the extraction of total phenolic compounds (TPC) and antioxidant capacity (AC) from three varieties of unripe grape juice by response surface method (RSM) using ultrasound-assisted extraction (UAE). The influence of temperature (25–65°C) and extraction time (5–30 min) on total phenolic content (TPC) and antioxidant capacity (DPPH and CUPRAC) was investigated. In this study, physicochemical properties, mineral composition, phenolic and organic acid components of three different verjuices were also investigated. As a result, the optimal extraction points for extraction time (12 min) and temperature (30°C) were determined. All independent variables were found to be significantly effective on TPC and AC content during UAE. Verjuices are a rich source of antioxidants, phenols, organic acids, minerals, and vitamin C. This study is expected to contribute to the evaluation of unripe grape wastes, which are very rich in bioactive components, and to increase its economic potential by expanding local production, thus contributing to sustainable agri-food processing.