flowers, known as elderberry flowers (EBF), are a plant tissue rich in polyphenolic phytochemicals with important bioactivities. However, there are few studies dealing with the production of ...polyphenol-containing EBF extracts. The objective of the investigation presented herein was the development of a high-performance green extraction methodology, to generate EBF extracts enriched in polyphenolic substances, using an efficient deep eutectic solvent, combined with ultrasonication pretreatment. The DES was composed of L-lactic acid (hydrogen bond donor-HBD) and glycine (hydrogen bond acceptor-HBA) and, after an initial screening to properly regulate HBD/HBA ratio, the extraction was optimized by deploying response surface methodology. Under the optimized conditions, which were DES/water (85%
/
), liquid-to-solid ratio 60 mL g
, and stirring speed 200 rounds per minute, the extraction yield in total polyphenols amounted to 121.24 ± 8.77 mg gallic acid equivalents per g dry matter. The integration of ultrasonication prior to the batch stirred-tank extraction boosted polyphenol recovery of up to 174.73 ± 2.62 mg gallic acid equivalents per g dry matter. Liquid chromatography-mass spectrometry analysis showed that the richest EBF extract obtained was dominated by rutin, a di-p-coumaroylquic acid and chlorogenic acid.
Context: The fruit of Lycium barbarum L. (Solanaceae), known as goji berry, has been exploited for a long time in traditional Chinese medicine. In recent decades, it has received much attention as ...one of the trendiest functional foods with a wide array of pharmacological activities in Western diets.
Objective: In this study the phenolic profile and potential antioxidant capacity of Lycium barbarum cultivated in Crete (Greece) were investigated.
Materials and methods: The berries were defatted with hexane and then extracted with dichloromethane and methanol using a Soxhlet apparatus. Furthermore, the methanol extract was fractionated with ethyl acetate and butanol. All fractions/extracts were tested for their antioxidant activity (DPPH, FRAP, chemiluminescence). Folin-Ciocalteu and LC-DAD-MS analyses were utilized for the identification of the phenolic compounds.
Results: The total phenolic content ranged from 14.13 ± 0.40 (water fraction) to 109.72 ± 4.09 (ethyl acetate fraction) mg gallic acid equivalent/g dry extract. Ethyl acetate extract exhibited the highest scavenging activities determined as EC
50
(4.73 ± 0.20 mg/mL) and IC
50
(0.47 ± 0.001 mg/mL) using DPPH and chemiluminescence assays. Seventeen phenolic compounds, including cinnamoylquinic acids and derivatives, hydrocinnamic acids and flavonoid derivatives, were tentatively identified. To the best of our knowledge, quercetin 3-O-hexose coumaric ester and quercetin 3-O-hexose-O-hexose-O-rhamnose are reported for the first time in goji berry fruits.
Discussion and conclusion: The results of this study suggest that consumption of goji berry fruits could serve as a potential source of natural antioxidant compounds and that goji berry phenolic extracts could be exploited for nutritional pharmaceutical purposes.
This study was undertaken to investigate the effects of hydrothermal treatments under mild acid and alkaline conditions on polyphenol release and recovery from wheat bran (WB). After an initial ...screening of various food-grade substances, strong evidence was raised regarding the potency of citric acid and sodium carbonate to provide WB extracts exceptionally enriched in polyphenols. Thus, these two catalysts were tested under various time and temperature combinations, and the processes were described by linear models based on severity factor. The most effective treatments were those performed with 10% of either citric acid or sodium carbonate, at a constant temperature of 90 °C for 24 h, providing yields in total polyphenols of 23.76 and 23.60 mg g
dry mass of ferulic acid equivalents, respectively. Liquid chromatography-mass spectrometry analyses revealed that, while the sodium carbonate treatment afforded extracts enriched in ferulic acid, treatments with citric acid gave extracts enriched in a ferulate pentose ester. The extracts produced from those treatments also exhibited diversified antioxidant characteristics, a fact ascribed to the different polyphenolic composition. To the best of the authors' knowledge, this is the first report demonstrating the effective release of ferulic acid and a ferulate pentose ester from WB, using benign acid and alkali catalysts, such as citric acid and sodium carbonate.
This investigation had as objective to study the effective recovery of olive leaf (OLL) polyphenols using a blend of an L-lactic acid/ammonium acetate deep eutectic solvent (DES) with β-cyclodextrin ...(β-CD). Following an initial DES screening, the extraction process was optimised with response surface methodology by implementing Box-Behnken design. The optimised extraction conditions thus determined were stirring speed 300 rpm, DES concentration 56.4% (w/w), liquid-to-solid ratio 100 mL g
−1
and β-CD concentration 0.7% (w/v). Maximum extraction yield (113.66 mg caffeic acid equivalents g
−1
dry mass) was achieved at 80 °C, without compromising antioxidant activity. Comparative assessment of the extraction medium DES/β-CD with other green solvents showed that it was a high-performing system providing polyphenol-enriched extract with improved antioxidant characteristics. Stability test of the extract obtained under optimal conditions performed over a period of 30 days at ambient conditions revealed that, while ferric-reducing power fluctuated within narrow limits, the antiradical activity was enormously enhanced by 100%. These changes in the antioxidant activity were not associated with the decline of major polyphenols in the OLL extract. However, the overall polyphenolic profile remained largely unchanged. It is suggested that the DES/β-CD is an efficient green solvent that may confer the OLL polyphenol extract satisfactory stability.
Eggplant peels were used to evaluate glycerol and ethanol for their ability to recover polyphenolic antioxidants. The evaluation was based on optimisation by a Box-Behnken experimental design and ...kinetics. The results showed that extraction with water/ethanol and water/glycerol mixtures, under optimised conditions, afforded virtually equal yield in total polyphenols, which was 13.40 and 13.51 mg caffeic acid equivalents per g dry weight, respectively. The extraction kinetics revealed that diffusion of phenolics in water/glycerol mixtures was slower (0.85 × 10
−12
m
2
s
−1
) compared with the one attained with water/ethanol (2.23 × 10
−12
m
2
s
−1
), yet the ability of both systems to recover essentially the same levels of total polyphenols was confirmed. The determination of total chlorogenates, total flavonoids and total pigments indicated that water/glycerol might be a more effective solvent system, but controversies were observed with regard to the antiradical activity and reducing power. The analytical polyphenolic profile of both extracts was dominated by chlorogenic acid and no major differences were recorded, a finding indicating that none of the solvent systems displayed selectivity. The results suggested that glycerol may be an ideal candidate for use in eco-friendly extraction processes.
The aim of this study was the examination of the effect of ultrasonication pretreatment and thermal treatment of soft wheat bran (SWB) with a novel acidic, tertiary deep eutectic solvent, composed of ...glycerol/citric acid/glycine, on the polyphenol extraction yield and antioxidant activity. This was achieved by sequentially deploying ultrasonication pretreatment and prolonged thermal treatment (extraction). Ultrasonication prior to stirred-tank extraction was shown to afford significantly higher total polyphenol yield compared to aqueous control solvents. Furthermore, thermal treatment had a striking effect on SWB polyphenol extraction, which increased from 6.31 ± 0.06 mg ferulic acid equivalents (FAE) g
− 1
dry mass (dm) (50 °C, 2.5 h) to 57.12 ± 1.14 mg FAE g
− 1
dm (90 °C, 24 h). Combination of ultrasonication pretreatment and thermal treatment boosted even more extraction yield at 94.62 mg FAE g
− 1
dm. Comparison of glycerol/citric acid/glycine with other common deep eutectic solvents demonstrated that this particular solvent was an exceptionally high-performing system. Liquid chromatography-tandem mass spectrometry analyses showed that the SWB extract produced with glycerol/citric acid/glycine deep eutectic solvent was dominated by polar compound(s), as opposed to acid and alkaline hydrolyzates, which contained virtually only ferulic acid. It was concluded that this investigation could be expanded by designing and screening task-specific deep eutectic solvents (DES) for improved extraction efficiency under less severe thermal treatment conditions. This would contribute towards the establishment of less energy-demanding processes for wheat bran polyphenol recovery.
The purpose of this study was to evaluate comparatively the polyphenolic content and the antioxidant activity of selected regional red and white wine varieties, produced in the Republic of North ...Macedonia. The polyphenolic content was evaluated by measuring the total polyphenol, total flavonoid, total tannin and total anthocyanin contents and the antioxidant activity by applying the DPPH (2,2-diphenyl-1-picrylhydrazyl), FRAP (ferric-reducing antioxidant power) and CUPRAC (cupric ion-reducing antioxidant capacity) assays. Statistical analysis of the results showed that all white wines examined (Smederevka, Temjanika and Zhilavka) belong to the same group, two red wines (Vranec and Kratoshija) belong to another group while the Stanushina red variety shows distinct differences from the other red wines examined.
This study was focused on the simultaneous organosolv treatment/extraction of waste orange peels (WOP) for the effective recovery of polyphenolic antioxidants. The treatments were performed with ...aqueous glycerol mixtures, which were acidified either with citric acid or hydrochloric acid (HCl). Process optimization was carried out using response surface methodology and comparative appraisal of the different processes tested, based on both the extraction efficiency factor (FEE), severity factor (SF) or combined severity factor (CSF). Metabolite stability was also of major concern, and it was examined by deploying liquid chromatography-mass spectrometry. The results drawn suggested 90% (w/w) glycerol to be the highest-performing system, providing a yield in total polyphenols of 44.09 ± 5.46 mg GAE g−1 DM at 140 °C for 50 min, with a FEE of 2.20 and an SF of 2.88. Acidification with 1% citric acid was proven less efficient and equally severe, whereas acidification with 1% HCl was less severe but also less efficient. The major disadvantage associated with the use of HCl was its detrimental impact on the polyphenolic composition of WOP since major metabolites, such as narirutin, hesperidin and didymin, did not survive the process. By contrast, the formation of lower molecular weight compounds was observed. With regard to antioxidant properties, the extract obtained with aqueous glycerol displayed significantly higher antiradical activity and reducing power, which was in line with its higher concentration in total polyphenols. It was concluded that organosolv treatment with aqueous glycerol under the conditions employed may boost polyphenol recovery from WOP, thus giving extracts with powerful antioxidant characteristics.
The current study aimed at developing an effective organosolv treatment, with the objective to obtain potato peel extracts highly enriched in polyphenols. To this end, two low-cost solvents were ...employed, 1- and 2-propanol, which are considered green, but they have been rather poorly studied compared to other conventional solvents, such as ethanol. Treatment development also embraced the use of sulfuric acid, a well-examined catalyst in organosolv processes. Treatment evaluation on the basis of response surface optimization and severity demonstrated that 1-propanol was a more effective solvent, providing a maximum yield in total polyphenols of 19.28 mg chlorogenic acid equivalents per g of dry potato peel weight, attained with 40% 1-propanol/1.5% (w/v) sulfuric acid at a treatment time of 60 min and a temperature of 90 °C. This treatment was of lower severity compared to the one with 2-propanol, and it also provided almost 24% higher total polyphenol yield. The extracts produced contained chlorogenic acid as the major constituent, accompanied by caffeic acid and minor amounts of p-coumaric acid. This is the first report on such an organosolv treatment of potato peels to recover polyphenolic compounds with high efficiency.
Low-transition temperature mixtures (LTTMs), also known as deep eutectic solvents, are liquid mixtures of natural substances that possess unique properties, not encountered with conventional ...solvents. Such liquids represent a state-of-the-art means of extracting bioactive plant constituents, yet the plethora of combinations of various substances that form LTTMs dictates detailed comparative testing, to identify LTTMs with high extraction capacity. In this study, a number of combinations of hydrogen bond donors (HBDs) with sodium acetate serving as the hydrogen bond acceptor (HBA), was attempted. The stable LTTMs formed were then used to extract antioxidant polyphenols and pigments from red grape pomace (RGP). The LTTM composed of L-lactic acid and sodium acetate at a molar ratio of 5:1 was found to be the most efficient solvent, giving a total polyphenol yield of 134.54 mg gallic acid equivalents per g of dry weight and a total pigment yield of 3.32 mg malvin equivalents per g of dry weight. The extract obtained with this particular LTTM also possessed the strongest antioxidant activity. The principal compounds in this extract were tentatively identified as phenolic acids, anthocyanin pigment derivatives and a flavonol glycoside.
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