Figure - available from: Journal of Food Measurement and Characterization
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Binding sites between β-casein (a, b) or αs1-casein (c, d) with kaempferol (a, c) or quercetin (b, d). Hydrogen-bonds are shown by green dashes
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Polyphenolic substances kaempferol and quercetin are major flavonols found in plant foods, while caseins are major protein fractions in milk. In this study, the non-covalent interactions involved in the formation of caseinate–flavonol complexes as well as the resultant scavenging activities to three free radicals were assessed by multi-spectroscopi...
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In this work, anion−π interactions between sulfate groups (SO42–) and protein aromatic amino acids (AAs) (histidine protonated (HisP), histidine neutral (HisN), tyrosine (Tyr), tryptophan (Trp), and phenylalanine (Phe)) in an aqueous environment have been analyzed using quantum chemical (QC) calculations and molecular dynamics (MD) simulations. Sul...
Citations
... The interaction between the two components usually reduces or enhances the antioxidant activity of phenolic substances while altering the protein structure [10,11]. The interaction is affected by environmental conditions and the types of structures involved, which leads to changes in the functional and nutritional properties of the complex [12][13][14]. For example, the interaction between chlorogenic acid and whey protein enhances the antioxidant activity of the complex [15], while the interaction between chlorogenic acid and bovine serum protein leads to the decline of the antioxidant activity of the complex [16]. ...
During the storage and processing of mung beans, proteins and polyphenols are highly susceptible to interactions with each other. Using globulin extracted from mung beans as the raw material, the study combined it with ferulic acid (FA; phenolic acid) and vitexin (flavonoid). Physical and chemical indicators were combined with spectroscopy and kinetic methods, relying on SPSS and peak fit data to statistically analyze the conformational and antioxidant activity changes of mung bean globulin and two polyphenol complexes before and after heat treatment and clarify the differences and the interaction mechanism between globulin and the two polyphenols. The results showed that, with the increase in polyphenol concentration, the antioxidant activity of the two compounds increased significantly. In addition, the antioxidant activity of the mung bean globulin–FA complex was stronger. However, after heat treatment, the antioxidant activity of the two compounds decreased significantly. The interaction mechanism of the mung bean globulin–FA/vitexin complex was static quenching, and heat treatment accelerated the occurrence of the quenching phenomenon. Mung bean globulin and two polyphenols were combined through a hydrophobic interaction. However, after heat treatment, the binding mode with vitexin changed to an electrostatic interaction. The infrared characteristic absorption peaks of the two compounds shifted to different degrees, and new peaks appeared in the areas of 827 cm−1, 1332 cm−1, and 812 cm−1. Following the interaction between mung bean globulin and FA/vitexin, the particle size decreased, the absolute value of zeta potential increased, and the surface hydrophobicity decreased. After heat treatment, the particle size and zeta potential of the two composites decreased significantly, and the surface hydrophobicity and stability increased significantly. The antioxidation and thermal stability of the mung bean globulin–FA were better than those of the mung bean globulin–vitexin complex. This study aimed to provide a theoretical reference for the protein–polyphenol interaction mechanism and a theoretical basis for the research and development of mung bean functional foods.
... Xiao and coauthors investigated the binding affinity of 50 dietary polyphenols to bovine milk proteins, and demonstrated that the binding affinity of the polyphenols to bovine milk proteins was related to the differences of polyphenol structure [37]. When kaempferol and quercetin noncovalently interacted with casein, it was found that quercetin with two −OH groups at the B-ring had higher affinity to caseinate than kaempferol only with one −OH group at the B-ring [38]. In addition, a previous study also reported that the energy changes (∆G) for the covalent interaction between galangin and whey proteins at 20-40 • C ranged from −32.8 to −35.9 kJ/mol, with calculated apparent binding parameters of (6.96-9.64) ...
It is recognized that minor dietary components polyphenols have anticancer effects on digestive tract, lung, leukemia, and other cancers, while polyphenols also can covalently or noncovalently interact with major dietary components proteins such as casein, soybean proteins, whey proteins, and bovine serum albumin. Thus, whether the noncovalent interaction between the molecules of two polyphenols (quercetin and fisetin) and two proteins (bovine serum albumin and casein) has positive or negative impact on anticancer activities of the polyphenols against human gastric adenocarcinoma AGS cells was assessed in this study. The two polyphenols had obvious anticancer activities to the cells, because dose levels as low as 20-160 mmol/L caused reduced cell viability of 30.0-69.4% (quercetin) and 24.6-63.1% (fisetin) (using a cell treatment time of 24 h), or 9.9-48.6% (quercetin) and 6.4-29.9% (fisetin) (using a cell treatment time of 48 h). However, the cell treatments by the polyphenols in the presence of the two proteins mostly caused lower polyphenol activity toward the cells, compared with those treatments by the polyphenols in the absence of the proteins. Specifically, the presence of the proteins led to reduced growth inhibition in the cells, because higher cell viability of 33.2-86.7% (quercetin) and 29.1-77.7% (fisetin) at 24 h, or 14.1-66.8% (quercetin) and 7.9-59.0% (fisetin) at 48 h, were measured in these treated cells. The two coexisting proteins also yielded the polyphenol-treated cells with less mitochondrial membrane potential loss, less formation of reactive oxygen species, and decreased cell apoptosis. Thus, it is highlighted that the noncovalent interaction between dietary polyphenols and proteins resulted in weakened anticancer ability for the polyphenols to the gastric cancer cells.
The heterogeneous antioxidant, namely, PS-2, 6-DTBP, was easily synthesized from chloromethylated polystyrene (CMPS) with 2, 6-di-tert-butylphenol by a simple one-step Friedel–Crafts reaction. As compared with CMPS (78 m2/g and 34.8 nm, respectively), the Brunauer–Emmett–Teller (BET) surface area (SBET) of PS-2, 6-DTBP was greatly increased to 623 m2/g, while the average pore size was sharply reduced to 7.0 nm. The antioxidative property of PS-2, 6-DTBP was extensively evaluated by the scavenging activity of superoxide and 2, 2-diphenyl-1-picrylhydrazyl radical (DPPH·) in inhibiting oxidation of benzaldehyde, and the results indicated that 2,6-di-tert-butylphenol loaded on PS-2, 6-DTBP had excellent capability in scavenging O2−· and DPPH·, and effectively inhibited the oxidation of benzaldehyde. As a heterogeneous antioxidant with free radical scavenger, PS-2, 6-DTBP can be conveniently separated from the liquid phase and is environment friendly, showing promising potential in solid antioxidant field.
This research aimed to extract and profile phenolic compounds from seed and fruit of Diospyros lotus, evaluate and compare the antioxidants and cytotoxic potential of the extracts. Seven phenolic acids and four other flavonoids extracts were subsequently obtained following different extraction methods. The extracts were evaporated, lyophilized, and prepared for RP-HPLC-DAD, MTT assay, and antioxidant evaluation by the ferrous ion chelating, ferric ion reducing power, FRAP, DPPH•, •OH and NO• scavenging methods. The RP-HPLC-DAD revealed an epigallocatechin, a flavonoid, and fourteen phenolic acids. Phenolic compounds with the highest concentrations are epigallocatechin (1460.80 ± 10.74 µg/gDW), gallic acid (1167.11 ± 4.04 µg/gDW) and t-cinnamic acid (244.45 ± 3.61 µg/gDW). The bound phenolic acids from acid hydrolysis-1 (BPAH-1) extract of the fruit sample exhibit the highest DPPH• activity, reducing power, and FRAP. The flavonol extract of the fruit sample unveils the highest Fe²⁺ chelating effect. The BPAH-1 and BPAH-2 extracts of the seed reveal the highest •OH and NO• activities, respectively. Seed sample gave the highest total phenolic/flavonoid/tannin contents. The cytotoxicity of the extracts on HepG2 cell lines > HeLa cell lines and the effects are more pronounced 48 h after treatments. Specifically, flavan-3-ol methanolic and BPAH-2 extracts of the seed, and flavan-3-ol methanolic and BPAH-1 extracts of the fruit show good cytotoxic effect against HepG2 cell lines (IC50 < 37 µg/mL). This research unveils the potential of D. lotus seed and fruit as possible antioxidant and anticancer agent. The antioxidant and cytotoxicity properties observed from the samples might be due to the phenolic compounds determined.
Graphical abstract
Protein-polyphenol interaction is a promising approach for enhancing the antioxidant activities of proteins. This review discusses the binding mechanism of proteins and polyphenols, including covalent bonding and non-covalent interactions such as van der Waals, hydrogen bonding, hydrophobic and electrostatic interactions. In addition, the review provides an overview of the effect of protein-polyphenol interactions on the structure and antioxidant activities of proteins as well as influencing factors, including polyphenol type and amount, pH, and fabrication method. Finally, future research direction is identified for further development of protein-polyphenol complexes/conjugates as food-based antioxidants.
