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1.
Food Chem ; 371: 131372, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34808772

RESUMO

To investigate antibacterial properties and application in food preservation of nanofibrous films (NFs), baicalin-liposomes (BCL-LPs) were loaded into polyvinyl alcohol-chitosan (PVA-CS) substrates to form NFs using electrospinning technology. The microstructure and phase identification of the NFs were characterized. The antibacterial properties and cytotoxicity of NFs were determined. The preservation of the NFs to mushrooms was evaluated. The results showed that smooth and uniform NFs were formed through molecular interaction between BCL-LPs and PVA-CS matrix. The NFs exhibited good antibacterial effects on Escherichia coli and Staphylococcus aureus due to the bacterial destruction resulting from the BCL delivery to bacterial cells by liposomes. In addition, the NFs were compatible with L929 fibroblasts. The BCL-LPs/PVA-CS NFs inhibited weight loss, browning, rancidity and bacterial growth as well as maintained the nutrients of mushrooms. The results show BCL-LPs/PVA-CS NFs possessed effective antibacterial properties, non-cytotoxicity and preservation performance, indicating the potential utilization as food-active packing.


Assuntos
Agaricales , Quitosana , Nanofibras , Antibacterianos/farmacologia , Flavonoides , Lipossomos , Álcool de Polivinil
2.
Food Chem ; 372: 131175, 2022 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-34653779

RESUMO

An accurate hydrophilic interaction liquid chromatography coupled mass spectrometry (HILIC-MS) method is presented to characterize starch digestion by α-amylase and measure the inhibition properties of flavonoids against α-amylase in vitro. Eleven products were found as 1 â†’ 4 linkage glucose oligosaccharides with different degrees of polymerization (DPs) from 2 to 12. The products with DPs of 2, 3, 6, 7, and 9 had higher yields. The product with DP of 9 had the highest yields, which first increased and then decreased with the reaction time. Pelargonidin has the best inhibition activity on all enzyme products. The 3'-hydroxyl of B-ring enhanced the inhibition activity of flavonol and flavone but weakened that of anthocyanin. The C-ring 3-hydroxyl increased the inhibition effect of flavonol on maltose but decreased that on the products with higher DPs than flavone. The HILIC-MS method can provide more detailed information on enzyme products for the study of flavonoids inhibiting α-amylase.


Assuntos
Flavonoides , alfa-Amilases Pancreáticas , Cromatografia Líquida , Interações Hidrofóbicas e Hidrofílicas , Espectrometria de Massas , Amido
3.
J Pharm Biomed Anal ; 207: 114435, 2022 Jan 05.
Artigo em Inglês | MEDLINE | ID: mdl-34715582

RESUMO

OBJECTIVE: To establish a rapid and comprehensive method for the quality evaluation of Plantaginis Semen (PS) by using near-infrared spectroscopy combined with chemometrics to determine the content of geniposidic acid (GEA), verbascoside (VE), isoverbascoside (IVE) and total flavonoids (TF) in PS, as well as the antioxidant activity (AOA). METHODS: The content of GEA, VE and IVE in PS were determined by HPLC, the content of TF in PS was determined by UV-Vis spectrophotometry, and the AOA of PS was characterized by the DPPH, ABTS and FRAP, respectively. Then, the measured values of each item were used as reference values and were correlated with the near infrared spectra of PS. Seven quantitative models were established by the partial least squares regression. A variety of spectral preprocessing, such as standard normal variation (SNV), multiplicative scatter correction (MSC), Savitzky-Golay smoothing (SG), derivative and their combination methods, were investigated. In addition, genetic algorithm (GA), particle swarm optimization (PSO), as well as competitive adaptive reweighted sampling (CARS) were also compared. All samples were divided into a calibration set and a prediction set at the ratio of 3:1 by the descending order of reference values. The coefficients of determination (R2), root mean square error (RMSE) and residual predictive deviation (RPD) were calculated to evaluate model performance. RESULTS: After optimization, the performance of each model was greatly improved, where the R2 for calibration and prediction were both greater than 0.8, the RPD were both greater than 2. Such satisfactory results indicated that the present models had good prediction accuracy. CONCLUSION: Quantitative models based on near infrared spectroscopy were herein established, which proved to be able to quickly and accurately determine the content of GEA, VE and IVE and TF, as well as AOA in PS, and which might provide a new method for rapid and comprehensive quality evaluation of PS.


Assuntos
Sêmen , Espectroscopia de Luz Próxima ao Infravermelho , Calibragem , Flavonoides , Análise dos Mínimos Quadrados
4.
Food Chem ; 366: 130593, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34314928

RESUMO

It is a common belief in China that aging could improve the quality of white tea. However, the stored-induced compositional changes remain elusive. In this study, ten subsets of white tea samples, which had been stored for 1-, 2-, 3-, 4-, 5-, 6-, 7-, 10-, 11- and 13- years, were selected. Macro-compositions were quantified firstly. As the results showed, it was interesting to find total flavonoids, thearubigins (TRs), and theabrownines (TBs) increasing, accompanied with a gradual decrease of total polyphenols, which suggest a conversion of phenolic component in the aging process. Then, nontargeted metabolomics was further conducted on selected subsets of samples, including 1-, 7- and 13- years stored to profile their conversion. As a result, most different metabolites were related to flavonol glycosides and flavone glycosides, suggesting dynamic phenolic component changes were vital in aging. The partial least-squares-discriminant analysis (PLS-DA) also identified them as markers in distinguishing.


Assuntos
Metabolômica , Chá , Flavonoides/análise , Polifenóis/análise
5.
Food Chem ; 366: 130597, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34314935

RESUMO

We investigated the effect of bee species identity and harvesting methods on the chemical composition and antiradical activity of 53 honey samples, produced by six stingless bee species in western Kenya (Kakamega forest). Our results illustrate that none of the assayed parameters significantly varied between the honey samples harvested by "punching holes" (n = 25) and "squeezing" (n = 28) methods. By contrast, species identity drove significant differences in the assayed parameters. Positive correlations between the antiradical activity and the phytochemicals (phenols and flavonoids) were observed, and honeys from Liotrigona sp. exhibited the highest amounts of phenols (214 mg GAE/100 g), flavonoids (73.0 mg QE/100 g) and antiradical activity (76.2%). The physicochemical analyses confirm the need to establish separate stingless bee honey standards for moisture, free acidity, invertase, electrical conductivity, and HMF, as these parameters significantly diverged from the set limits for Apis mellifera honey.


Assuntos
Mel , Himenópteros , Animais , Abelhas , Flavonoides , Quênia , Simpatria
6.
Food Chem ; 366: 130689, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34343950

RESUMO

This research established the optimal conditions for infusion extraction (IE) and ultrasound-assisted extraction (UAE) of bioactive components from laver (Porphyra dentata) using response surface methodology (RSM) and artificial neural network coupled with genetic algorithm (RSM-ANN-GA). The variables, temperatures (60, 80, and 100 ℃) and times (10, 15, and 20 min) were designed to optimise total phenolic, total flavonoid, total amino acid, a* value, and R-phycoerythrin content of laver extract. The optimised condition for IE and UAE was achieved at 60 ℃ for 18.08 min and 80.66℃ for 14.76 min in RSM while showing 60 ℃ for 19 min and 80℃ for 15 min in the RSM-ANN-GA mode, respectively. Results revealed that RSM-ANN-GA provided better predictability and greater accuracy than the RSM model and laver extract from UAE gave the higher values of responses compared to those from IE. These findings highlight the high-efficient extraction method along with better statistical approach.


Assuntos
Porphyra , Flavonoides , Redes Neurais de Computação , Fenóis , Extratos Vegetais
7.
Food Chem ; 367: 130682, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34364147

RESUMO

Basil is an edible, aromatic plant, which makes the study of the ecotoxicity of metals in plant metabolism relevant. Given the above, the objective of this study was to evaluate the effects of metals, aluminum, lead, and cadmium, in the synthesis of phenolic compounds and in the dry mass of basil plants (O. basilicum L.) grown in a hydroponic system. The plants were subjected to four different concentrations of cadmium (0.2, 0.6, 1.2, and 1.8 mmol L-1), lead and aluminum (0.04, 0.08, 0.12, and 0.16 mmol L-1), and compared with the control. After desiccation of the plant material, the total dry mass was obtained and then, hydroethanolic extracts (43% distilled water and 57% ethanol) were made for biochemical analyzes, which consisted of the determination of caffeic acid (CA) and rosmarinic acid (RA) by high performance liquid chromatography analysis with a diode detector (HPLC-DAD); total phenolics (TP) and total flavonoids (TF) by spectrophotometry. The data were submitted to analysis of variance and multivariate analysis (principal component analysis-PCA and hierarchical cluster analysis-HCA) was applied for data association. The phenolic compounds showed a high positive correlation with each other, and the total dry mass showed low and negative correlations with the analyzed variables. The results showed that the metals aluminum, lead, and cadmium promoted a stress condition in basil plants, which resulted in the reduction of the dry matter mass and an increase in the synthesis of phenolic compounds, according to the type and concentration of the metal.


Assuntos
Ocimum basilicum , Antioxidantes , Cádmio , Ácidos Cafeicos , Cinamatos , Depsídeos , Flavonoides , Chumbo , Análise Multivariada
8.
Food Chem ; 367: 130744, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34384977

RESUMO

Conventional methods for determining phenolics and their bioactive properties are expensive, time-consuming, and laborious. This hinders the quality control of red propolis, recognized for having different types of phenolic constituents with different bioactive properties, for example, its antioxidant properties. In this sense, we present a new application of near and medium infrared spectroscopy to predict phenolic constituents, total flavonoids, gallic acid, kaempferol, pyrocatechin, quercetin, and different antioxidant tests (DPPH radical, reducing power and protection of the ß-carotene: linoleic acid system) of red propolis using chemometry. The optimized models showed good predictive capacity with a minimum correlation coefficient of 0.70, low associated error, and figures of merit that indicate the good predictive capacity in the validation of the models. These data show infrared spectroscopy as efficient to simultaneously predict nine quality analyzes of red propolis quickly and simply. This also avoids tedious procedures for traditional chromatographic and spectrophotometric tests.


Assuntos
Própole , Antioxidantes , Flavonoides , Análise Multivariada , Fenóis , Espectrofotometria Infravermelho
9.
Food Chem ; 366: 130605, 2022 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-34311239

RESUMO

The Citrus genus is a good source of dietary flavonoids, which have many health benefits. As a representative citrus fruit, the flavonoids composition in Shatianyu (Citrus grandis L. Osbeck) pulp remains to be investigated. In the present study, 11 flavonoids were isolated and identified from Shatianyu pulp flavonoid extracts (SPFEs). Among them, 4 flavonoids were previously undescribed and 2 flavonoids were firstly isolated from pummelo. The cellular antioxidant activity (CAA) and oxygen radical absorbance capacity (ORAC) of isolated compounds were evaluated. Naringin and rhoifolin showed the highest ORAC activity, and the presence of a 3-hydroxy-3-methylglutaryl or a 4'-glucose decreased the ORAC activity of flavonoids. The contribution of isolated flavonoids to the holistic antioxidant activity of SPFEs was determined by an online knockout method. Melitidin, bergamjuicin and naringin contributed most to ORAC activity, while bergamjuicin, melitidin and apigenin-4'-O-ß-d-glucopyranosyl-7-O-α-l-rhamnopyranosyl-(1 â†’ 2)-[6″-O-(3- hydroxy-3-methylgltaryl)]-ß-d-glucopyranoside contributed most to CAA activity.


Assuntos
Citrus , Antioxidantes , Flavonoides , Extratos Vegetais , Polifenóis
10.
Spectrochim Acta A Mol Biomol Spectrosc ; 265: 120383, 2022 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-34536893

RESUMO

In this work, we explore the excited-state intramolecular proton transfer (ESIPT) mechanisms and relative solvent effects for three novel 3-hydroxylflavone derivatives (i.e., HOF, SHOF, and NSHOF) in acetonitrile, dichloromethane, and toluene solvents. Through calculations, we optimize the structures of HOF, SHOF, and NSHOF. Through the analysis of a series of structural parameters related to hydrogen bonding interactions, it could be found that the hydrogen bonds of the three derivatives are all enhanced in the S1 state, and more importantly, the excited-state hydrogen bonds of HOF are stronger than those of SHOF and NSHOF. In order to explore the effects of solvent polarity, we analyze the core-valence bifurcation (CVB) index, infrared (IR) vibration spectrum, and the potential energy curves. We find that for HOF, SHOF, and NSHOF, the strength of the excited-state hydrogen bonds increases as the solvent polarity decreases. The solvent polarity dependent ESIPT mechanisms pave the way for further designing novel flavonoid-based solvatofluorochromic probes in future.


Assuntos
Flavonoides , Prótons , Ligação de Hidrogênio , Modelos Moleculares , Solventes
11.
Food Chem ; 369: 130968, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34479013

RESUMO

Lipids usually contain a large ratio of polyunsaturated fatty acids (PUFAs), which are highly susceptible to oxidation. Presence of oxidized lipids in foods may affect the bioavailability of lipophilic bioactive components after ingestion. In this study, the effect of oxidized and unoxidized linoleic acid (LA) on the transport of a highly lipophilic bioactive citrus flavonoid (5-hydroxy - 6, 7, 8, 4' tetramethoxylflavone or 5-DMT) was determined using a Caco-2 cell model. Results demonstrated that compared to free 5-DMT, unoxidized LA improved the trans-enterocyte absorption of 5-DMT by stimulating the production of lipid droplets and chylomicrons. Although the amount of 5-DMT transported across the enterocyte doubled by oxidized LA compared to free 5-DMT, it significantly induced reactive oxygen species (ROS), affected the function of tight junction and caused damages to the morphology of enterocyte monolayer. This study re-emphasized the importance of preventing lipid oxidation in foods.


Assuntos
Citrus , Ácido Linoleico , Células CACO-2 , Quilomícrons , Enterócitos , Flavonoides , Humanos
12.
Food Chem ; 368: 130800, 2022 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-34403997

RESUMO

The work explored the process of ultrasound-assisted adsorption/desorption to efficiently purify jujube peel flavonoids (JPFs) using macroporous resins (MRs). The impact of ultrasound power and temperature on the adsorption/desorption features of JPFs on MRs were studied. The maximum adsorption (80.21 ± 2.11 mg/g) /desorption (76.22 ± 1.68 mg/g) capacity of total flavonoids content were obtained. The pseudo-second-order kinetic and Freundlich isotherm models better described the whole process of ultrasound-assisted adsorption. The adsorption process was spontaneous, physical, and dominated by multilinear intraparticle diffusion. Ultrasound mainly enhanced the adsorption capacity by strengthening the formation of hydrogen bonds and increasing the surface roughness of MRs. Besides, the principal individual flavonoid ((+)-Catechin, (-)-Epicatechin, Rutin, Quercetin-3-O-robinobioside) content of JPFs in ultrasound treatment was 2-3 times that of shaking treatment, and biological activities were significantly increased. Overall, as a low-cost green technology, ultrasound can improve the properties of MRs and better purify JPFs.


Assuntos
Flavonoides , Ziziphus , Adsorção , Extratos Vegetais , Resinas Vegetais , Resinas Sintéticas
13.
Food Chem ; 368: 130864, 2022 Jan 30.
Artigo em Inglês | MEDLINE | ID: mdl-34438172

RESUMO

Ultra-high pressure (UHP) is a novel non-thermal pretreatment method in food processing for improving the extraction yield of polyphenols and functional properties. The present work investigated the phenolic profiles, antioxidant activities, and cytoprotective effects of the free, esterified, and insoluble-bound phenolic fractions from mango leaves before and after ultra-high pressure (UHP) treatment. UHPLC-Q-Orbitrap-MS/MS analysis resulted in the identification of 42 phenolic compounds in the different phenolic forms. UHP pretreatment could significantly influence the contents of total phenols, total flavonoids and individual compounds in the different phenolic fractions (p < 0.05). After UHP pretreatment, these phenolic fractions exhibited greater antioxidant activity, and inhibited reactive oxygen species production and cell apoptosis (p < 0.05). Meanwhile, IBP were the most potential antioxidative and cytoprotective ingredients. Therefore, UHP pretreated mango leaves with enhanced bioactivity could be used as biological agents in the health food industry to improve its application and economic values.


Assuntos
Antioxidantes , Mangifera , Antioxidantes/farmacologia , Cromatografia Líquida de Alta Pressão , Flavonoides/análise , Fenóis/análise , Extratos Vegetais/farmacologia , Folhas de Planta/química , Espectrometria de Massas em Tandem
14.
Food Chem ; 369: 130932, 2022 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-34461511

RESUMO

Nanobubbles (NBs) generated-nanojets membrane poration have gained enormous attention. In this study, NBs were fabricated as a novel green approach to assist ionic liquid (IL) [C4C1im][BF4] extraction of polyphenols from Carya cathayensis Sarg. husk. NBs were successfully generated with mean size of 85.47 ± 5 nm, zeta potential of +39 ± 2.24 mV, and concentration of 21.15 ± 0.75 × 108 particles/mL (stable for over 48 h in IL solution). Compared to common solutions extract, IL-NBs extract showed significantly higher (p < 0.05) antioxidant activity and polyphenols yields with a total polyphenol, total flavonoid, and total tannins contents of 85.67 ± 2.05 mg GAE/g DW, 42.44 ± 1.17 mg CE/g DW, and 8.2 ± 0.05 mg TAE/g DW, respectively. The SEM results confirmed that NBs' nanojets caused morphological destruction of the husk powder. Overall, IL-NBs solution showed better extraction efficiency of polyphenols than other solutions, giving insight into a new "green" nanotechnology-based extraction method.


Assuntos
Carya , Líquidos Iônicos , Antioxidantes , Flavonoides , Polifenóis
15.
Food Chem ; 370: 130979, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34543921

RESUMO

Hops are abundant in natural bioactive compounds. In this work, nine prenylated bitter compounds from hop were evaluated for their inhibitory activity against α-glucosidase. As a result, four flavonoids and one phloroglucinol (lupulone, LP) outperformed acarbose in inhibiting α-glucosidase. Isoxanthohumol (IX) and LP with two types of structures were selected for inhibition mechanism studies by spectroscopic methods and molecular dynamics simulation (MD). Results showed that IX acted as noncompetitive inhibitor and bound to α-glucosidase in allosteric sites via hydrogen bonds, hydrophobic, van der Waals (vdW), and electrostatic force, whereas LP was uncompetitive inhibitor and bound to catalytic sites via hydrophobic and vdW interactions. Notably, the conformation around binding site of α-glucosidase formed stable α-helix and tightened after binding IX and LP, respectively, which helped to elucidate noncompetitive and uncompetitive inhibitory mechanisms. This work demonstrated that two types of prenylated bitter compounds are discrepant in their mechanisms of interaction with α-glucosidase.


Assuntos
Humulus , Simulação por Computador , Flavonoides , Paladar , alfa-Glucosidases
16.
Food Chem ; 371: 131125, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34563971

RESUMO

Tartary buckwheat has higher health-promoting value than common buckwheat. However, the related metabolites information except flavonoids is largely deficient. Here, we compared the seed metabolomes of the two species using a UHPLC-QqQ-MS-based metabolomics approach. In total, 722 metabolites were obtained, of which 84 and 78 were identified as the key active ingredients of Traditional Chinese Medicines and the active pharmaceutical ingredients for six major diseases-resistance, respectively. Comparative analysis showed there were obviously difference in metabolic profiles between the two buckwheat species, and further found 61 flavonoids and 94 non-flavonoids metabolites displayed significantly higher contents (≥2 fold) in Tartary buckwheat than in common buckwheat. Our results suggest that Tartary and common buckwheat seeds are rich in metabolites beneficial to human health, and non-flavonoids metabolites also contributed to Tartary buckwheat's higher health-promoting value than common buckwheat. This study provides valuable information for the development of new functional foods of Tartary buckwheat.


Assuntos
Fagopyrum , Flavonoides , Humanos , Metabolômica , Sementes
17.
Food Chem ; 371: 131122, 2022 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-34571406

RESUMO

Tea seed oil is rich in phenols with good antioxidant capacity. However, the antioxidant capacity evaluation of tea seed oil polyphenols is not deep enough, which mainly focusing on the evaluation of the chemical system. Thirty-nine phenols were tentatively identified by UPLC-ESI-MS/MS analysis, including flavonoids and phenolic acids. The antioxidant capacity of phenol extracts was investigated in vitro and in vivo. The chemical assays showed the extracts had good proton and electron transfer capabilities. The CAA assay indicated the IC50 of the extracts was 77.93 ± 4.80 µg/mL and cell antioxidant capacity of the extracts was 101.05 ± 6.70 µmol·QE/100 g of oil. The animal experiments suggested phenol extracts could significantly improve the organ index, reduce malondialdehyde content, and increase superoxide dismutase, glutathione peroxidase and total antioxidant capacity (p < 0.05). This study was contributed to the antioxidant capacity of phenol extracts of tea seed oil by comprehensive evaluation.


Assuntos
Antioxidantes , Espectrometria de Massas em Tandem , Antioxidantes/análise , Flavonoides/análise , Fenóis/análise , Extratos Vegetais , Óleos Vegetais , Chá
18.
Food Chem ; 370: 130981, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34500290

RESUMO

In the present study, 14 structurally unique flavonoids were screened to systematically investigate structural requirements for selectively inhibiting human α-amylase versus α-glucosidase to obtain a slow but complete starch digestion for health benefit. The selective inhibition property of three flavonoids chosen against the two classes of starch digestive enzymes was confirmed through various analytical techniques - in vitro inhibition assay, fluorescence quenching, kinetic study, and molecular modeling. Considering the chemical structure of flavonoids, the double bond between C2 and C3 and OH groups at A5 and B3 are critical for the inhibition of α-amylase allowing flavonoids to lie parallel on the α-amylase catalytic active site, whereas the OH groups at B3 and C3 are important for α-glucosidase inhibition causing B-ring specific entry into the catalytic active site of α-glucosidase. Our findings provide insights into how to apply flavonoids to effectively control digestion rate for improving physiological responses.


Assuntos
alfa-Amilases , alfa-Glucosidases , Flavonoides , Humanos , Amido
19.
Food Chem ; 370: 131265, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34788950

RESUMO

Yellowing is a critical issue that reduces quality and commodity value of rice. This article presents an overview on rice yellowing and the mechanism of rice yellowing was addressed as the emphasis. The change of physicochemical and nutritive properties in yellowed rice depends on the exposure temperature and time, as well as rice cultivar. The temperature and moisture on rice yellowing were dominant. There is no consensus on the relationship between microorganisms and rice yellowing. The occurrence of yellowing is mainly associated with heat stress induced by heaping heat or respiration of grain, and the yellowing is the collective result of primary and secondary metabolism. The upregulation of flavonoids is the direct cause of rice yellowing, which can be used as metabolic markers of rice yellowing. The Maillard reaction also contributes to yellowing during storage. Aeration and cooling are recommended to lessen the occurring of rice yellowing during commercial storage.


Assuntos
Oryza , Temperatura Baixa , Flavonoides , Metabolismo Secundário
20.
Food Chem ; 370: 131292, 2022 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-34788954

RESUMO

Iron-flavonoid interactions in iron-fortified foods lead to undesirable discolouration. This study aimed to investigate iron-mediated complexation, oxidation, and resulting discolouration of flavonoids by spectrophotometric and mass spectrometric techniques. At pH 6.5, iron complexation to the 3-4 or 4-5 site instantly resulted in bathochromic shifting of the π â†’ π* transition bands, and complexation to the 3'-4' site (i.e. catechol moiety) induced a π â†’ dπ transition band. Over time, iron-mediated oxidative degradation and coupling reactions led to the formation of hydroxybenzoic acid derivatives and dehydrodimers, respectively resulting in a decrease or increase in discolouration. Additionally, we employed XRD, SEM, and TEM to reveal the formation of insoluble black metal-phenolic networks (MPNs). This integrated study on iron-mediated complexation and oxidation of flavonoids showed that the presence of the C2-C3 double bond in combination with the catechol moiety and either the 4-carbonyl or 3-hydroxyl increased the intensity of discolouration, extent of oxidation, and formation of MPNs.


Assuntos
Flavonoides , Ferro , Oxirredução , Fenóis , Espectrofotometria
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