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Polynomial equations and statistical parameters calculated after implementation of a 2 3 -full factorial, central composite experimental design.
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Aqueous mixtures of glycerol and 2-hydroxypropyl-β-cyclodextrin (CD), two non-toxic eco-friendly substances, were used as a means of extracting antioxidant polyphenols from oak acorn (Quercur robur) husks. The process was optimized by implementing a central composite (Box-Behnken) experimental design and response surface methodology, taking into co...
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Context 1
... screening carried out was designed to evaluate the effect of three selected variables, that is, the CD concentration (C CD ), glycerol concentration (C gl ) and temperature (T). The values of the responses (Y TP , A AR and P R ) obtained experimentally were analyzed by multiple regression and after removal of the non-significant factors (p > 0.05), the theoretical models were as shown in Table 2. The significance of model fitting was assessed using the square coefficient of correlation (R 2 ), which was over than 0.93 (p < 0.05). ...Context 2
... significance of model fitting was assessed using the square coefficient of correlation (R 2 ), which was over than 0.93 (p < 0.05). This outcome clearly pointed to a statistically significant match between observed and predicted responses, and that the models given in Table 2 can predict the optimal experimental conditions with high reliability. Values of the independent process variables (X 1 , X 2 and X 3 ) considered, as well as measured and predicted values for all responses, are analytically given in Table 3. ...Context 3
... screening carried out was designed to evaluate the effect of three selected variables, that is, the CD concentration (CCD), glycerol concentration (Cgl) and temperature (T). The values of the responses (YTP, AAR and PR) obtained experimentally were analyzed by multiple regression and after removal of the non-significant factors (p > 0.05), the theoretical models were as shown in Table 2. The significance of model fitting was assessed using the square coefficient of correlation (R 2 ), which was over than 0.93 (p < 0.05). ...Context 4
... significance of model fitting was assessed using the square coefficient of correlation (R 2 ), which was over than 0.93 (p < 0.05). This outcome clearly pointed to a statistically significant match between observed and predicted responses, and that the models given in Table 2 can predict the optimal experimental conditions with high reliability. Values of the independent process variables (X1, X2 and X3) considered, as well as measured and predicted values for all responses, are analytically given in Table 3. ...Context 5
... the mathematical model revealed a positive effect of C CD (Table 2), which suggested that increasing C CD up to 13% (w/v) contributed in obtaining higher Y TP . Such a phenomenon would be reasonably anticipated because ligand inclusion in the CD cavity is a stoichiometric phenomenon and usually only one molecule may be incorporated into the cavity so as to become entrapped. ...Context 6
... A AR of the extracts was positively influenced by C gl , but the interaction term of C CD with T and the quadratic term of C gl have also had a significant and positive effect. On the contrary, the quadratic term of C gl had a negative effect on A AR ( Table 2). The trend recorded for P R shared some similar features, but no quadratic terms of any variable tested were significant. ...Citations
... Multiple studies have reported that glycerol is a viscous solvent, so 70% aqueous glycerol was used. Higher concentrations would not extract higher yields of anthocyanins [32,34,37,39]. The extraction temperature plays a critical role in the recovery of anthocyanins. ...
Aqueous glycerol is a proposed green extractant for anthocyanins and polyphenols as an alternative to conventional solvents. The aim of this study was to investigate the potential use of aqueous glycerol to extract anthocyanins from Syzygium cumini fruit pulp with high yields. The ultrasound-assisted extraction process was also examined to enhance the extraction yield. The application of ultrasound-assisted extraction along with glycerol as a modifier remarkably enhanced the extraction of anthocyanins compared to the conventional extraction. Aqueous glycerol (70%) was screened against conventional solvents (ethanol, methanol and water), where glycerol showed promising outcomes. The optimised ultrasonication time and extraction temperature (25 °C for 5 min) were selected based on our previous study of NADESs. The results showed that glycerol gave the highest amount of anthocyanin content (201.05 mg C3G/100 g fresh weight) compared to conventional solvents for retrieving anthocyanins from S. cumini fruit pulp. Besides the anthocyanin content, the extract yield, phenolic content, and antioxidant activities using DPPH and FRAP were also determined. Glycerol showed a higher phenolic recovery (0.9 mg GAE/g dry sample), resulting in higher antioxidant activity (DPPH activity-73.35% inhibition). Therefore, the application of UAE with aqueous glycerol provides accessibility and enhanced anthocyanin extraction efficiency, thus fulfilling the green and sustainable approach to anthocyanin extraction.
... Mota et al. [149] characterized the acorns of Q. suber as a raw material for sourcing phenolic compounds. Such use was also indicated by Kyriakidou et al. [150]. Górnaś [74] indicated the possibility of obtaining γand β-tocopherol from acorns (Q. ...
Acorns, the fruit of oak trees of the genus Quercus, have been known to people for generations worldwide. In ancient times, they were an important part of culinary traditions and folk medicine. Their exploitation for food over the years has been significantly diminished, which may arise from the high content of tannins responsible for a bitter taste and anti-nutritional properties. However, more and more studies show acorns’ potential nutritional and health benefits. Furthermore, new reports are emphasizing the health-promoting properties of tannin-decomposition products. This review aims to present the available studies on the phytoconstituents variation in the acorns of different Quercus species and their possible significance for food and medical applications. In this study, the results of lab-scale food processing, as well as in vivo and in vitro experiments, are included. The literature data proved that acorn products (flour, oil, and extracts) are intensively examined due to their dietary, antioxidant, anti-microbial, anti-inflammatory, anti-cancer, and neuroprotective activities provided by their bioactive compounds. The general conclusion is that this raw material can be used more widely in the future as an ingredient in functional foods, supplements, and drugs.
... The dried material was mixed with solvent (liquid-to-solid ratio = 20:1 (mL/g)) in a stoppered glass bottle, composed of either distilled water, or aqueous solutions of β-CD (1.84% w/v, maximum solubility and optimized yield extraction) or HP-β-CD (13% w/v, optimized yield extraction) according to previous findings (Kyriakidou et al., 2016). The plant material was subjected to three different extraction conditions: a) under continuous stirring at 600 rpm for 120 min in a water bath at 25 ± 1 • C (25CEx), b) under continuous stirring at 600 rpm for 120 min in a water bath at 85 ± 1 • C (85CEx), and c) in a water bath at 25 • C by using the ultrasonic Bandelin Sonoplus HD 3200 apparatus with the VS 70/T probe (Bandelin, Berlin, Germany), where the total energy applied to the medium was ~ 23,000 kJ (25UEx). ...
Plant anthocyanins have widely been employed as natural food colorants. However, their instability restricts many of their applications in food industry. In this study, anthocyanins were extracted from onion outer scales, using aqueous solutions with or without added cyclodextrins (CDs). The results indicated that when cyclodextrins were included in the extraction medium, the anthocyanins were stable or even had improved and augmented color intensity upon storage or following thermal and UV-light treatments over a broad pH range (2.0-7.0). FT-IR and UV-Vis spectroscopy measurements confirmed the formation of inclusion complexes between CDs and anthocyanins and the presence of pyranosyl groups (pyranoanthocyanins) upon heating. Overall, the stability of onion anthocyanins under various environmental stresses, often encountered during food processing and storage, indicates that the natural color extract from onion outer scales can be of value as an interesting colorant alternative for food applications.
... A more recent study showed that β-CD may act as a very effective co-solvent when combined with glycerol to recover OLL polyphenols [28]. The same was also observed for the extraction of oak acorn phenolics using a blend of 2-hydroxypropyl β-cyclodextrin and glycerol [29]. Investigations involving polyphenol extraction using mixtures of DES and cyclodextrins were in concurrence, emphasising the role of cyclodextrins as polyphenol extraction boosters [11,12]. ...
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.
... It can be modified (e.g., hydroxypropyl-β-CD, hydroxyethyl-β-CD, methyl-β-CD) in order to tackle drawbacks related to low aqueous solubility, such as other polysaccharides [214,217]. It is worth mentioning that aqueous solutions of cyclodextrins have been used also as enhancers for the green extraction of polyphenols of a variety of plant materials, e.g., pomegranate fruit [218], Sideritis scardica [219], oak acorn husks [220], etc. Chitosan is a natural, non-toxic, biodegradable, biocompatible, cationic polysaccharide that derives from the alkaline deacetylation of chitin. The latter is the second-most abundant polymer in nature, after cellulose, and it is of low cost as it is obtained from marine waste. ...
Plants constitute a rich source of diverse classes of valuable phytochemicals (e.g., phenolic acids, flavonoids, carotenoids, alkaloids) with proven biological activity (e.g., antioxidant, anti-inflammatory, antimicrobial, etc.). However, factors such as low stability, poor solubility and bioavailability limit their food, cosmetics and pharmaceutical applications. In this regard, a wide range of delivery systems have been developed to increase the stability of plant-derived bioactive compounds upon processing, storage or under gastrointestinal digestion conditions, to enhance their solubility, to mask undesirable flavors as well as to efficiently deliver them to the target tissues where they can exert their biological activity and promote human health. In the present review, the latest advances regarding the design of innovative delivery systems for pure plant bioactive compounds, extracts or essential oils, in order to overcome the above-mentioned challenges, are presented. Moreover, a broad spectrum of applications along with future trends are critically discussed.
... Therefore, there is a need to increase the shelf life of fruits and vegetables in order to limit the wastages, to reduce the cost of disposal and environmental issues regarding food wastes (Salehi, 2019a(Salehi, , 2019b [55,56] . Fruits and vegetables are excellent source of highly potential phytochemicals and have been studied for the extraction of polyphenols, various pigments, polysaccharides, proteins, dietary fibers, enzymes, flavor and aroma compounds and so on (Ran et al., 2019;Sharma et al., 2017;Kowalska et al., 2017) [47,61,30] . The wastes of fruits and vegetables have these valuable bioactive compounds comprise health beneficial attributes like anticancer, antimutagenic, antiviral, antioxidant, antitumor as well as reduces the risks of cardiometabolic diseases (Sharma et al., 2017) [61] . ...
... This enhances their antioxidant property which further enhance their solubility (Fang & Bhandari, 2010) [14] . Aqueous solutions of cyclodextrins considered as green solvents as there is a complex formation between hydrophobic cyclodextrin cavities and non-polar components which leads to reduce the free energy of system (Kyriakidou et al., 2016) [30] . LC-MS was done to identify the different polyphenols and colorants present in the extract. ...
... This enhances their antioxidant property which further enhance their solubility (Fang & Bhandari, 2010) [14] . Aqueous solutions of cyclodextrins considered as green solvents as there is a complex formation between hydrophobic cyclodextrin cavities and non-polar components which leads to reduce the free energy of system (Kyriakidou et al., 2016) [30] . LC-MS was done to identify the different polyphenols and colorants present in the extract. ...
... Combination of water/glycerol solutions with cyclodextrin as co-solvent for the recovery of polyphenolic substances have also been reported. Using oak (Quercur robur) acorn husks as plant matrix, polyphenol yield was optimized with 60% (w/v) glycerol and 13% (w/v) 2-hydroxypropyl βcyclodextrin (HP-β-CD), at 80 °C [39]. Identical values for glycerol, HP-β-CD and temperature were also determined for the optimization of pigment (anthocyanin) extraction from onion solid wastes [41]. ...
The acknowledgement that uncontrolled and excessive use of fossil resources has become a prime concern with regard to environmental deterioration, has shifted the orientation of economies towards the implementation of sustainable routes of production, through the valorization of biomass. Green chemistry plays a key role in this regard, defining the framework of processes that encompass eco-friendly methodologies, which aim at the development of highly efficient production of numerous bioderived chemicals, with minimum environmental aggravation. One of the major concerns of the chemical industry in establishing sustainable routes of production, is the replacement of fossil-derived, volatile solvents, with bio-based benign ones, with low vapor pressure, recyclability, low or no toxicity, availability and low cost. Glycerol is a natural substance, inexpensive and non-toxic, and it is a principal by-product of biodiesel industry resulting from the transesterification process. The ever-growing market of biodiesel has created a significant surplus of glycerol production, resulting in a concomitant drop of its price. Thus, glycerol has become a highly available, low-cost liquid, and over the past decade its use as an alternative solvent has been gaining unprecedented attention. This review summarizes the utilization of glycerol and glycerol-based deep eutectic mixtures as emerging solvents with outstanding prospect in bioactive polyphenol extraction.
... Conversely, the extraction carried out with ultrasound produced an extract with higher polyphenolic content but lower antioxidant activity than those obtained from sub-critical water at 170 and 190 °C. The influence of solvent composition and temperature in the polyphenol content of acorn extracts was evaluated by Kyriakidou et al. [77]. The authors indicated that optimum extraction condition for polyphenols and antioxidant activity was obtained using a solvent composed of water, glycerol, and 2-hydroxypropyl-β-cyclodextrin (27:60:13) at 80 °C. ...
The use of synthetic antioxidants in the food industry has raised important questions about the effects of prolonged consumption on human health. On top of that, the consumption of meat products has been changing due to the awareness generated by health-related organizations. In this sense, exploring strategies to develop and produce healthier meat products has become a paramount concern. Several studies explored the composition of several seeds to characterize and explore the compounds with antioxidant activity, which are mainly composed of polyphenols. The use of antioxidant extracts in meat products has shown important results to delay the oxidative reactions in meat products derived from the processing and storage of meat products. Moreover, these extracts can also replace synthetic antioxidants and preserve the quality of meat products. Therefore, the aims of this review are first, to present the sources and compounds with antioxidant activity in seeds, and second, to discuss their protective effect against oxidative reactions in meat products.
... Inclusion complex formation with polyphenols increases their antioxidant activity which may be attributed to an increase of their solubility [14]. Aqueous solutions of cyclodextrins could be considered as alternative, green solvents, since upon formation of complexes involving the hydrophobic CD cavities and non-polar compounds, a reduction of the system's free energy can be achieved [15]. Moreover, CDs are non-toxic ingredients that can be used in pharmaceutical, cosmetic and food applications [16]. ...
... By using both glycerol and CD as the extraction medium higher extractions yields of polyphenols can be achieved (ß75% higher than ethanol extraction) [15]. Consequently, other effective, but in some cases undesirable or adverse extraction solvents, such us ethanol or water/ethanol mixtures [30], can be avoided. ...
The valorization of onion (Allium cepa) solid wastes, a 450,000 tonnes/year waste in Europe, by a green extraction method is presented. Polyphenols of onion solid wastes were extracted using eco‐friendly solvents, such as water and glycerol. The 2‐hydroxypropyl‐β‐cyclodextrin was also used as a co‐solvent for the augmentation of the extraction yield. The process has been optimized by implementing a central composite face centered design of experiments, with two replicates in the central point, taking into consideration the following independent variables: glycerol concentration, cyclodextrin concentration and temperature. The assessment of the extraction model was based on two responses: the total pigment yield and the antiradical capacity. LC‐MS analysis was also employed in order to identify polyphenols and colourants of the obtained extracts. The main polyphenols found were quercetin and quercetin derivatives and the main colourant was cyanidin 3‐O‐glucoside. The extract was also tested as a food colourant in a yoghurt matrix. The onion leaf extract was found to be a stable natural colourant and could be utilized as an alternative ingredient to synthetic coloring agents.
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... Furthermore, cyclodextrin encapsulation of polyphenols contributes in higher stability and controlled release [9]. Recent studies showed that combining 2-hydroxypropyl β-cyclodextrin with aqueous glycerol may effectively increase yield of polyphenol extraction [10,11]. Similar results were reported for water extraction of apple flavonols, using various cyclodextrins [12]. ...
... With reference to the effect of C CD , the optimal value determined by the model was 9% (w/v), which is fairly close to 7% (w/v) required for polyphenol extraction from olive leaves with aqueous glycerol [11]. However, 13% (w/v) 2-hydroxypropyl β-cyclodextrin was determined as optimal for polyphenol extraction from oak acorn with aqueous glycerol [10]. Moreover, recovery of polyphenols from grape pomace was shown to be optimal using 1% (w/v) β-cyclodextrin in either 80% aqueous ethanol or water, whereas recoveries declined at higher β-cyclodextrin concentration [28]. ...
... This finding pointed clearly to a boosting of the extraction yield triggered by the addition of the CD in the DES, evidencing its improved effectiveness. It is to be noted that the use of various cyclodextrins, such as β-cyclodextrin [29,33] or 2hydroxypropyl β-cyclodextrin [10,11], in combination with aqueous solvents resulted in increased extraction yields, suggesting that cyclodextrins can effectively enhance extraction efficiency. However, such an effect is for the first time reported for combination of DES and CD. ...
A novel deep eutectic solvent (DES) with optimised composition was used to evaluate the effect of methyl β-cyclodextrin (CD) on the efficiency of polyphenol extraction from Olea europaea leaves (OLLs). The process developed was based on a 2³ full-factorial design and response surface methodology to assess the simultaneous effect of CD concentration (CCD), liquid-to-solid ratio (RL/S) and temperature (T). Under optimised conditions (CCD = 9%, RL/S = 40 mL g⁻¹, T = 51 °C), the yield in total polyphenols (YTP) was 116.65 ± 3.60 mg gallic acid equivalents per g dry weight. This value was significantly higher than that determined for the extraction performed with 60% aqueous ethanol. The extraction kinetics also showed that the extraction rate was slowed down in the presence of CD, yet the higher extraction capacity of the DES/CD medium was confirmed. Characterisation of the extracts obtained with DES/CD and DES by means of liquid chromatography-mass spectrometry demonstrated that there was no selective extraction of any particular polyphenol, suggesting that CD acted merely as an extraction booster.
