In this study, phenolic metabolites in their free, soluble esterified, and soluble glycosylated forms in green tea infusions and cell wall-bound forms in solid residues obtained by ultrasound ...treatment, agitation treatment, and normal infusion preparation method were investigated. In total, thirty-three phenolic compounds were characterized including twenty-two flavonoids and eleven phenolic acids using UPLC-DAD-QToF/MS analysis. The flavonoids were sub-characterized as flavanols and flavonols, and phenolic acids were sub-characterized as hydroxybenzoic acid, hydroxybenzoylquinic acid, hydroxycinnamic acid, and hydroxycinnamoylquinic acid. As flavanols, EGCG was dominant in their free form and was significantly higher (p < 0.05) in ultrasound (4094 mg/100 g) and agitation (3906 mg/100 g) treatment than normal infusion (1657 mg/100 g). Kaempferol was predominant flavonols in their free form and was significantly higher (p < 0.05) in ultrasound (54.78 mg/100 g) and agitation (53.87 mg/100 g) treatment than normal infusion (30.67 mg/100 g). In contrary, cell wall-bound phenolics were dominated by gallic acid and were significantly higher (p < 0.05) in normal solid residues (2582 mg/100 g) than agitation (527 mg/100 g) and ultrasound (157 mg/100 g) treatment. This study provides a useful database of different forms of phenolic metabolite profiling of aqueous green tea infusions and solid residues.
•Characterize green tea phenolic metabolites using UPLC-DAD-QToF/MS analysis.•Ultrasonic and agitation treatment is best to extract each form of phenolics.•Extraction techniques could increase soluble phenolic yields in green tea infusion.
Polyphenols have become an intense focus of research interest due to their health-beneficial effects especially in the treatment and prevention of several chronic diseases. Polyphenols are known to ...form complexes with proteins leading to changes in the structural, functional and nutritional properties of both compounds. In this review, the effects of protein–phenolic interactions under various conditions on protein and phenolic compound's structure and functionality are described. The parameters that are defined to affect protein–phenolic interactions are basically temperature, pH, protein type and concentration, and the type and structure of phenolic compounds. Even though the exact mechanism of how proteins influence polyphenols is still not yet known, studies on the changes in the structure and functional properties were investigated. According to these studies, secondary and tertiary structures of the proteins are changed, and solubility of the protein is decreased whereas its thermal stability might be improved. In addition, the amount of some amino acids and protein digestibility might be reduced as a result of this interaction. It is also concluded that proteins significantly decrease the antioxidant capacity in general, but there are some controversial results which might be due to the differences in the analytical techniques performed in these studies. Similarly, different results were obtained in the bioavailability experiments. Factors affecting these results as well as lacking parts of these studies are discussed in detail in this review. In conclusion, interaction of proteins and phenolic compounds is a complex phenomenon and should be further investigated. On the other hand, optimum conditions should be studied in detail to improve the food processes and provide maximum beneficial health effects to the consumers with optimum nutritional and functional properties.
► The affecting factors on protein-phenolic interactions are discussed. ► Protein-phenolic interactions affect functional, nutritional properties of proteins. ► Determination of phenolic contents, total antioxidant capacities is also affected. ► Bioavailability of phenolics changes as a result of protein-phenolic interactions.
For the first time, characteristics of free (FPCs), soluble esterified-bound (SEBPCs), soluble glycosylated-bound (SGBPCs) and insoluble-bound (ISBPCs) phenolic compounds in Chinese organic hawthorn ...berry (Crataegus pinnatifida) were investigated along with antioxidant activity. A total of 22 phenolics were identified and quantified by HPLC-ESI-MS/MS, with the most abundant being (−)-epicatechin (750 ± 4 μg/g dw)>procyanidin B2 (375 ± 3 μg/g dw)>(+)-catechin (305 ± 5 μg/g dw)>chlorogenic acid (256 ± 4 μg/g dw). Overall, flavonoids were the predominant phenolic sub-class in FPCs, ISBPCs and SEBPCs, whereas SGBPCs mostly existed as phenolic acids. In addition, more than 85.0% of procyanidins were found in FPCs, and no procyanidins were presented in SGBPCs. (+)-Catechin, (−)-epicatechin and protocatechuic acid were the main phenolics in ISBPCs, FPCs/SEBPCs and SGBPCs, respectively. 35.3–37.8% of antioxidant activity in hawthorn berry were contributed by FPCs, followed by ISBPCs (25.0–27.0%)>SEBPCs (23.4–25.7%)>SGBPCs (9.4–15.7%), and significant positive correlations were observed between phenolics and antioxidant activity. Interestingly, antioxidant activity of ISBPCs in peel (103 ± 2–125 ± 4 μmol Trolox/g dw) was significantly higher compared to pulp (61.3 ± 1.3–67.3 ± 1.4 μmol Trolox/g dw) as well as phenolics (1000 ± 35>368 ± 29 μg/g dw). The outcomes would help to provide better understanding of the functional activities of hawthorn berry and help utilize the advantage of this “medicine food homology” fruit for the application in food and pharmaceutical industries.
•First report on soluble and insoluble-bound phenolics (ISBPCs) in hawthorn berry.•Free/glycosylated form was the main/least contributor to antioxidant activity (AC).•Over 24% of AC was contributed by ISBPCs, and catechin was the predominant ISBPCs.•Epicatechin was found to be the major (free) phenolic compound in hawthorn berry.•Hawthorn berry fruit could serve as good source of phenolic antioxidants.
Summary
Peel and seeds of red‐skinned passion fruit, mango, longan, rambutan, white‐flesh and red‐flesh dragon fruit were screened for their in vitro antioxidant activity, and determination of a ...detailed profile of phenolic compounds. Rambutan peel and mango seed extracts exhibited the highest total phenolic content and antioxidant activities (DPPH, ABTS and FRAP values). By using UPLC‐QTOF‐MS/MS analysis, the profiles of soluble and bound phenolics in the fruit by‐products were obtained. Ellagic acid, geraniin, quercetin hexoside, gallic and galloyshikimic acid were predominant in rambutan peel, whereas, mangiferin, ellagic acid and galloy(di)glucoside were the major phenolic compounds in mango seed. Main phenolic compounds in longan peel were ellagic acid, galloyldiglucoside, and gallic acid, while in dragon fruit peel this was isorhamnetin glycoside, isorhamnetin glucorhamoside. Meanwhile, rutin and quercetin hexoside were predominant in passion fruit peel. These findings contribute significantly to the database of phenolic profiles of by‐products of tropical fruits.
Tropical fruit by‐products are potential sources of phenolic compounds. In vitro antioxidant activity and phenolic content of fruit peel and seeds were determined. Using UPLC‐qTOF‐MS/MS, phenolic profiles of the fruit by‐products are presented.
•The phenolics recovery is influenced by the solvolytic solution.•Three extraction steps increase up to 10% phenolics recovery.•α-Amylase pre-treatment of the residue remarkably increased bound ...phenolics extraction.•Phenolic acids extractability is favored by the reduction of matrix viscosity.
The effects of the type of solvolytic solution and number of extraction steps on the recovery of free phenolics, anthocyanins and proanthocyanidins from different rice samples were evaluated. Moreover, bound phenolic acids were determined as a function of enzymatic and/or alkaline hydrolysis treatment of the rice residue obtained after the extraction of free phenolics. The Acetone/Water (70:30 v/v) was the most effective solvolytic solution for extracting free phenolics from pigmented rice, as well as anthocyanins from black and wild rice, and proanthocyanidins from red rice. The application of three extraction steps increased the recovery of free phenolics up to 10%. The adoption of an enzymatic treatment, with α-amylase in order to reduce the paste viscosity of the residue, increased the extractability of bound phenolics. α-Amylase at 37°C during 15min followed by an alkaline hydrolysis at 37°C was the best treatment for the recovery of bound phenolics.
The aim of this study was to isolate, identify and quantify soluble free phenolics, conjugated acid-hydrolysable phenolics (AHP) and alkaline-hydrolysable phenolics, and bound phenolics (BP) ...fractions from two tomato varieties (saladette and grape) and an industrial tomato by-product, as well as, to determine their antioxidant capacity. Phenolic composition was determined using Folin–Ciocalteu’s method and HPLC–DAD. AHP were predominant in grape and saladette tomato extracts (91.47 ± 17.28 mg gallic acid equivalents (GAE) per g dry extract (DE) and 57.41 ± 8.80 mg GAE per g DE, respectively), while BP form was predominant in tomato by-product (51.30 ± 10.91 GAE per g DE). AHP extract of grape tomato presented the highest antioxidant capacity by DPPH assay (252.35 ± 42.55 μmol trolox equiv (TE) per g DE). In the case of ORAC assay, AHP fractions from both grape (1005.19 ± 138.52 μmol TE per g DE) and saladette tomatoes (804.16 ± 131.45 μmol TE per g DE), and BP fraction from by-product (852.40 ± 71.46 μmol TE per g DE) showed the highest ORAC values. Caffeic acid was the most abundant phenolic acid and it was found mainly in its conjugated forms. Naringenin was the most abundant flavonoid and it was mainly detected in bound form. Our analysis allowed a better characterization of phenolic compounds in whole tomato and by-product, remarking the importance of the fractionation. The valorization of the industrial tomato by-product, through the use of its different fractions of phenolic antioxidant compounds, could generate additional income to the tomato industry and reduce the waste disposal problem.
The presence of emerging contaminants in environmental aqueous matrices is an ever-growing problem, since conventional wastewater treatment methods fail to adequately remove them. Therefore, the ...application of non-conventional methodologies such as advanced oxidation processes is of great importance to tackle this modern problem. Photocatalysis as well as catalytic activation of persulfates are promising techniques in this field as they are capable of eliminating various emerging contaminants, and current research aims to develop new materials that can be utilized for both processes. In this light, the present study focused on the use of a simple sol-gel-combustion methodology to synthesize Cu-substituted LaNiO3 perovskite materials in an attempt to improve the photocatalytic and catalytic performance of pure LaNiO3, using molar ratios of Cu:Ni that have not been previously reported in the literature. The morphological, structural, and optical features of the synthesized materials were characterized by a series of analytical techniques (e.g., X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electron microscopy, diffuse reflectance spectroscopy, etc.). Also, their performance as photocatalysts, persulfate anion activators and simultaneously as photocatalysts/persulfate anion activators (hybrid) was evaluated by conducting laboratory-scale experiments using phenol (phenolics) as a model emerging contaminant. Interestingly, the results revealed that LaCu0.25Ni0.75O3 exhibited the best efficiency in all the applied processes, which was mainly attributed to the introduction of oxygen vacancies in the structure of the substituted material. The contribution of selected reactive species in the hybrid photocatalytic/catalytic experiments utilizing LaCu0.25Ni0.75O3 as a (photo)catalyst was investigated using appropriate scavengers, and the results suggested that singlet oxygen is the most dominant. Additionally, the stability of all synthesized perovskites was assessed by monitoring the concentration of the leached Cu and/or Ni cations at the end of every applied process. Finally, the reusability of LaCu0.25Ni0.75O3 was evaluated in three consecutive catalytic cycles using the hybrid experiment methodology, as this process demonstrated the best efficiency in terms of phenolics removal, and the results were rather promising.
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•Substitution of Ni by Cu increased SSA and decreased Eg.•LaCu0.25Ni0.75O3 exhibited the best photocatalytic and catalytic performance.•Hybrid process (photocatalysis + catalytic PS activation) was the most effective.•Metal leaching of LaCu0.25Ni0.75O3 was similar to that of LaNiO3.•LaCu0.25Ni0.75O3 retained most of its (photo)catalytic activity after three cycles.
This study was conducted to evaluate total phenolic content, antioxidant activity, total carotenoids and phenolic compounds of ginger (Zingiber officinale) rhizomes dried using different drying ...methods (oven, microwave, freeze and room-air drying). Freeze-dried ginger rhizomes exhibited significantly (p < 0.05) higher total phenolics (931.94 mgGAE/100 g), antioxidant activity (82.00%) and total carotenoids (13.17 μg/g) than those dried using other techniques. Oven-dried ginger showed higher values for all individual phenolic compounds detected in this study as compared to those dried using other methods. The dominant phenolic compounds of dried ginger included (+)-catechin (250.02 mg/100 g), gallic acid (197.03 mg/100 g) and 3, 4-dihydroxybenzoic acid (116.07 mg/100 g). Drying of ginger rhizome using oven and freeze-drying methods my result in improved contents of bioactive compounds and higher antioxidant activity. Correlation analyses for biochemical composition of ginger rhizomes showed that total phenolics were positively correlated with antioxidant activity (r2 = 0.973, p < 0.001).
•Ginger rhizome contains valuable bioactive compounds with health properties.•Drying of ginger may affect its biologically important chemical constituents.•A comparative study of oven, microwave, freeze and air drying of ginger.•Freeze dried ginger had higher total phenolics and total carotenoids.•Oven dried ginger showed improved phenolic compounds availability.
•The design of the experiment enabled the study the effects of UV and temperature on phenolics.•UV radiation stimulated accumulation of flavonoids, anthocyanins and methoxycinnamic acid.•Temperature ...was a major factor influencing concentrations of rosmarinic, p-anisic and vanillic acid.•The non-invasive fluorescence method can be used to estimate flavonoid content in lettuce.•The trends of phenolic compound accumulation in green and red genotypes were similar.
Environmental conditions influence the content and metabolic profile of phenolic compounds in vegetables. The present study focused on distinguishing between the effects of ultraviolet (UV) radiation and temperature on lettuce plants with green or red leaf color when grown in either a greenhouse or outdoors. A combination of the non-destructive, fluorescence-based method with spectrophotometric and HPLC analyses enabled us to assess the effects of environment, cultivar, and plant-leaf color on concentrations of flavonoids, anthocyanins, and phenolic compounds. The accumulation of total phenolics, flavonoids, anthocyanins, and phenolic acids (benzoic acid derivatives and cinnamic acid derivatives) increased in direct sunlight (high UV radiation, moderate temperature) conditions outdoors as compared to the greenhouse conditions (low UV radiation, high temperature). The comparison of the effects of UV radiation and temperature (indoor-outdoor effect) indicated that the level of UV radiation plays a dominant role in the accumulation of flavonoids, anthocyanins, and methoxycinnamic acid; while temperature predominantly influences the accumulation of phenolic acids (rosmarinic, p-anisic, vanillic acid. Although, the leaf color (green vs. red) was strongly related to the content of majority of studied phytochemicals, environmental conditions affected their concentrations in both color types similarly. The concentrations of compounds estimated with the non-invasive, fluorescence excitation ratio method were highly consistent with those obtained by standard analytical approaches. Our results show that this fast, non-invasive method can be effectively used for determining concentrations of flavonoids and phenolic acids in lettuce plants.
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