Revealing the potential effects of oil phase on the stability and bioavailability of astaxanthin contained in Pickering emulsions: In vivo, in vitro and molecular dynamics simulation analysis.

This study investigated the effects of oil phases on the encapsulation rate, storage stability, and bioavailability of astaxanthin (ASTA) in Pickering emulsions (PEs). Results showed PEs of mixed oils (olive oil/edible tea oil) had excellent encapsulation efficiency (about 96.0%) and storage stability of ASTA. In vitro simulated gastrointestinal digestion results showed the mixed oil PE with a smaller interfacial area and higher monounsaturated fatty acid content may play a better role in improving ASTA retention and bioaccessibility. In vivo absorption results confirmed the mixed oil PE with an olive oil/edible tea oil of 7:3 was more favorable for ASTA absorption. Molecular dynamics simulation showed ASTA bound more strongly and stably to fatty acid molecules in the system of olive oil/edible tea oil of 7:3; and van der Waals force was the main binding force. NMR further proved there really were interactions between ASTA and four main fatty acids.

Identification of Novel Peptides in Distillers' Grains as Antioxidants, α-Glucosidase Inhibitors, and Insulin Sensitizers: In Silico and In Vitro Evaluation.

Distillers' grains are rich in protein and constitute a high-quality source of various bioactive peptides. The purpose of this study is to identify novel bioactive peptides with α-glucosidase inhibitory, antioxidant, and insulin resistance-ameliorating effects from distiller's grains protein hydrolysate. Three novel peptides (YPLPR, AFEPLR, and NDPF) showed good potential bioactivities, and the YPLPR peptide had the strongest bioactivities, whose IC50 values towards α-glucosidase inhibition, radical scavenging rates of 2,2'-azino-bis (3-ethylbenzothiazoline-6- sulfonic acid) (ABTS) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) were about 5.31 mmol/L, 6.05 mmol/L, and 7.94 mmol/L, respectively. The glucose consumption of HepG2 cells treated with YPLPR increased significantly under insulin resistance condition. Moreover, the YPLPR peptide also had a good scavenging effect on intracellular reactive oxygen species (ROS) induced by H2O2 (the relative contents: 102.35% vs. 100%). Molecular docking results showed that these peptides could stably combine with α-glucosidase, ABTS, and DPPH free radicals, as well as related targets of the insulin signaling pathway through hydrogen bonding and van der Waals forces. This research presents a potentially valuable natural resource for reducing oxidative stress damage and regulating blood glucose in diabetes, thereby increasing the usage of distillers' grains peptides and boosting their economic worth.

Polysaccharides from Polygonatum kingianum Collett & Hemsl ameliorated fatigue by regulating NRF2/HO-1/NQO1 and AMPK/PGC-1α/TFAM signaling pathways, and gut microbiota.

Polygonatum kingianum Coll & Hemsl is an important Chinese medicine used for enhancing physical function and anti-fatigue, and polysaccharides (PKPs) are considered as the main bioactive components. However, the mechanisms through which PKPs exert their anti-fatigue effects are not fully understood. This study aimed more comprehensively to explore the anti-fatigue mechanisms of PKPs, focusing on metabolism, protein expression, and gut flora, by using exhaustive swimming experiments in mice. Results showed a significant increase in the exhaustive swimming time of the mice treated with PKPs, especially in the high-dose group (200 mg/kg/day). Further studies showed that PKPs remarkably improves several fatigue-related physiological indices. Additionally, 16S rRNA sequence analysis showed that PKPs increased antioxidant bacteria (e.g., g_norank_f_Muribaculaceae) and the production of short-chain fatty acids (SCFAs), while reducing the abundance of harmful bacteria (e.g., g_Escherichia-Shigella and g_Helicobacter). PKPs also mitigated oxidative stress through activating the NRF2/HO-1 signaling pathway, and promoted energy metabolism by upregulating the expression of AMPK/PGC-1α/TFAM signaling pathway proteins. This research may offer theoretical support for incorporating PKPs as a novel dietary supplement in functional foods targeting anti-fatigue properties.

Exploring the Blood Glucose-Lowering Potential of the Umami Peptides LADW and EEAEGT Derived from Tuna Skeletal Myosin: Perspectives from α-Glucosidase Inhibition and Starch Interaction.

This study aimed to explore the potential of umami peptides for lowering blood glucose. Molecular docking results showed that the peptides LADW and EEAEGT bound to the active amino acid residues of α-glucosidase via hydrogen bonds and Van der Waals forces, a finding supported by an independent gradient model (IGM). Molecular dynamics (MD) simulations demonstrated that the peptides LADW and EEAEGT can decelerate the outward expansion of α-glucosidase and reduce amino acid fluctuations at the active site. In vitro findings indicated that the peptides LADW and EEAEGT showed potent inhibitory activity against α-glucosidase, with IC50 values of 4.40 ± 0.04 and 6.46 ± 0.22 mM, respectively. Furthermore, MD simulation and morphological observation results also revealed that LADW and EEAEGT alter starch structure and form weak interactions with starch through intermolecular hydrogen bonding, leading to the inhibition of starch hydrolysis. Peptides inhibit the ability of starch to produce reducing sugars after simulated gastrointestinal digestion, providing additional evidence of the inhibition of starch hydrolysis by the added peptides. Taken together, these findings suggest that consuming the umami peptides LADW and EEAEGT may alleviate postprandial blood glucose elevations via inhibiting α-glucosidase and starch hydrolysis.

Chinese Sumac (Rhus chinensis Mill.) Fruits Prevent Hyperuricemia and Uric Acid Nephropathy in Mice Fed a High-Purine Yeast Diet.

Hyperuricemia (HUA) is a prevalent chronic disease, characterized by excessive blood uric acid levels, that poses a significant health risk. In this study, the preventive effects and potential mechanisms of ethanol extracts from Chinese sumac (Rhus chinensis Mill.) fruits on HUA and uric acid nephropathy were comprehensively investigated. The results demonstrated a significant reduction in uric acid levels in hyperuricemia mice after treatment with Chinese sumac fruit extract, especially in the high-dose group, where the blood uric acid level decreased by 39.56%. Visual diagrams of the kidneys and hematoxylin and eosin (H&E)-stained sections showed the extract's effectiveness in protecting against kidney damage caused by excessive uric acid. Further investigation into its mechanism revealed that the extract prevents and treats hyperuricemia by decreasing uric acid production, enhancing uric acid excretion, and mitigating the oxidative stress and inflammatory reactions induced by excessive uric acid in the kidneys. Specifically, the extract markedly decreased xanthine oxidase (XOD) levels and expression in the liver, elevated the expression of uric acid transporters ABCG2, and lowered the expression of uric acid reabsorption proteins URAT1 and SLC2A9. Simultaneously, it significantly elevated the levels of endogenous antioxidant enzymes (SOD and GSH) while reducing the level of malondialdehyde (MDA). Furthermore, the expression of uric-acid-related proteins NLRP3, ACS, and Caspase-3 and the levels of IL-1ß and IL-6 were significantly reduced. The experimental results confirm that Chinese sumac fruit extract can improve HUA and uric acid nephropathy in mice fed a high-purine yeast diet. This finding establishes a theoretical foundation for developing Chinese sumac fruit as a functional food or medicine for preventing and treating HUA.

The profiles of free, esterified and insoluble-bound phenolics in peach juice after high pressure homogenization and evaluation of their antioxidant capacities, cytoprotective effect, and inhibitory effects on α-glucosidase and dipeptidyl peptidase-â £.

The phenolic profiles, antioxidant capacities, cytoprotective effect, and α-glucosidase and DPP-IV inhibitory capacity of free (FP), esterified (EP) and insoluble-bound (IBP) phenolic fractions in 'Lijiang snow' peach juice after high pressure homogenization (HPH) were investigated, and the molecular docking was used to explore the enzyme inhibition mechanism. HPH increased total phenolic and total flavonoid contents in three fractions without changing compositions. The IC50 of radicals scavenged by three fractions were all reduced by HPH. The best inhibition on intracellular ROS production were found for phenolic fractions after HPH at 300 MPa, with ROS levels ranged within 95.26-119.16 %. HPH at 300 MPa reduced the apoptosis rates of FP and EP by 16.52 % and 9.33 %, respectively. All phenolic fractions showed effective inhibition on α-glucosidase and DPP-IV by formation of hydrogen bonding and van der Waals forces. This study explored the feasibility of HPH to enhance the phenolics and bioactivity of peach juice.

Exploring the Transmembrane Behaviors of Dietary Flavonoids under Intestinal Digestive Products of Different Lipids: Insights into the Structure-Activity Relationship In Vitro.

This study aimed to investigate the transmembrane transport behavior and structure-activity relationships of various dietary flavonoids in the presence of dietary lipids derived from different sources in vitro. Results revealed that the digestion products of soybean oil (SOED) and lard (LOED) augmented the apparent permeability coefficients of most dietary flavonoids, and SOED exhibited higher transport compared with LOED. The structural properties of flavonoids and the potential interactions between fatty acids in these digestion products and flavonoids may influence the outcomes. 3D quantitative structure-activity relationship analyses revealed that incorporating small-volume groups at position 8 of the A-ring augmented the transmembrane transfer of flavonoids in the LOED system compared with the control group. By contrast, the integration of hydrophobic groups at position 5 of the A-ring and hydrogen bonding acceptor groups at position 6 of the A-ring enhanced the transmembrane transportation of flavonoids in the SOED system. Molecular dynamics simulations revealed that the SOED system may facilitate the interactions with flavonoids to form more stable and compact fatty acid-flavonoid complexes compared to the LOED system. These findings may provide valuable insights into flavonoid absorption to facilitate the development and utilization of functional foods or dietary supplements based on dietary flavonoids.

The Gastroprotective Effect of Walnut Peptides: Mechanisms and Impact on Ethanol-Induced Acute Gastric Mucosal Injury in Mice.

The objective of this research was to explore the protective impact of walnut peptides (WP) against ethanol-induced acute gastric mucosal injury in mice and to investigate the underlying defense mechanisms. Sixty male BALB-c mice were divided into five groups, and they were orally administered distilled water, walnut peptides (200 and 400 mg/kg bw), and omeprazole (20 mg/kg bw) for 24 days. Acute gastric mucosal injury was then induced with 75% ethanol in all groups of mice except the blank control group. Walnut peptides had significant protective and restorative effects on tissue indices of ethanol-induced gastric mucosal damage, with potential gastric anti-ulcer effects. Walnut peptides significantly inhibited the excessive accumulation of alanine aminotransferase (ALT), aspartate transferase (AST), and malondialdehyde (MDA), while promoting the expression of reduced glutathione (GSH), total antioxidant capacity (T-AOC), glutathione disulfide (GSSG), and mouse epidermal growth factor (EGF). Furthermore, the Western blot analysis results revealed that walnut peptides significantly upregulated the expression of HO-1 and NQO1 proteins in the Nrf2 signaling pathway. The defensive impact of walnut peptides on the gastric mucosa may be achieved by mitigating the excessive generation of lipid peroxides and by boosting cellular antioxidant activity.

Transmembrane behaviors and quantitative structure-activity relationship of dietary flavonoids in the presence of intestinal digestive products from different carbohydrate sources based on in vitro and in silico analysis.

Bioavailability plays a key role for flavonoids to exert their bioactivities. This study investigated the transmembrane transport behavior and structure-activity of dietary flavonoids. Results showed that the apparent permeability coefficients of some flavonoids could be significantly increased when digestion products from rice flour (RD) or wheat flour (WD) are present (p < 0.05), especially in the WD, potentially due to higher reducing sugar (p < 0.05). 3D-QSAR revealed that the hydrogen bond acceptor groups at positions 5 and 6 of ring A, small-volume groups at position 3', hydrophobic groups at position 4', and large-volume groups at position 5' of ring B increased the transmembrane transport of flavonoids in the WD. A hydrogen bond donor group at position 4' of ring B enhanced the transmembrane transport of flavonoid compounds in the RD. These findings contribute to our comprehensive understanding of flavonoid absorption within the context of intestinal carbohydrate digestion.

Identification of Novel Umami Peptides in Termitornyces albuminosus (Berk) Heim Soup by In Silico Analyses Combined with Sensory Evaluation: Discovering Potential Mechanism of Umami Taste Formation with Molecular Perspective.

In this study, 24 peptides were identified in Termitornyces albuminosus (Berk) Heim soup, 12 of which were predicted to possess an umami taste based on the BIOPEP-UWM or Umami-MRNN databases. Among these 12 peptides, four peptides (i.e., QNDF, QGGDF, EPVTLT, and EVNYDFGGK) exhibited the lowest affinity energy with the umami receptor type 1 member 1 (T1R1) subunit. Molecular docking and molecular dynamics simulation further confirmed the strong binding of these four umami peptides to the umami receptor T1R1/T1R3, with the EVNYDFGGK forming the most stable complex. After synthesizing the four peptides, their umami taste was validated through sensory and electronic tongue analyses with recognition thresholds ranging from 0.0938 to 0.3750 mmol/L. Notably, the EVNYDFGGK peptide displayed the strongest umami taste (recognition threshold, 0.0938 mmol/L). This study may contribute to the industrial development of T. albuminosus by providing a new understanding of the mechanism of its umami formation.

Effect of inoculating Pichia spp. starters on flavor formation of fermented chili pepper: Metabolomics and genomics approaches.

The influence of Pichia spp. on flavor formation and metabolic pathways during chili pepper fermentation was investigated in this study. Multiple omics approaches were employed, including metabolomics analysis to identify volatile and non-volatile flavor compounds, and genomic analysis to gain insights into the underlying molecular mechanism driving flavor formation of chili peppers inoculated with Pichia spp. The results showed that inoculation with Pichia spp. accelerated fermentation process of chili peppers compared to spontaneous fermentation. Metabolomics analysis showed P. fermentans promoted characteristic terpenes [e.g., (Z)-ß-ocimene and linalool], L-glutamate, gamma-aminobutyric acid, and succinate production, while P. manshurica produced more alcohols (e.g., isoamyl alcohol and phenylethyl alcohol) and phenols (e.g., 4-ethylguaiacol and 2-methoxy-4-methylphenol). Genomics analysis revealed that a substantial portion of the genes in Pichia spp. were associated with amino acid and carbohydrate metabolism. Specifically, the pathways involved in amino acid metabolism and the release of glycoside-bound aromatic compounds were identified as the primary drivers behind the unique flavor of fermented chili peppers, facilitated by Pichia spp.

Chinese Sumac Fruits (Rhus chinesis Mill.) Alleviate Type 2 Diabetes in C57BL/6 Mice through Repairing Islet Cell Functions, Regulating IRS-1/PI3K/AKT Pathways and Promoting the Entry of Nrf2 into the Nucleus.

This research aimed to probe the potential alleviative effects of ethanol extracts of Chinese sumac (Rhus chinesis Mill.) fruits against type 2 diabetes mellitus (T2DM) in C57BL/6 mice induced by high-fat/high-fructose diet (HFFD) and streptozotocin. The results showed that the ethanol extracts could significantly regulate blood glucose levels, glycosylated hemoglobin, blood lipids, insulin, and insulin resistance, while also restoring endogenous oxidative stress. Pathological and immunohistochemical analyses revealed that the extracts partially restored the physiological function of islet cells. Furthermore, Western blotting results suggested that the extracts could regulate the protein expression in IRS-1/PI3K/AKT signaling pathway, and immunofluorescence findings demonstrated their potential to promote the translocation of Nrf2 into the nucleus. This study elucidated a novel finding that ethanol extracts derived from Chinese sumac fruits have the potential to alleviate symptoms of T2DM in mice. Moreover, these findings could offer valuable scientific insights into the potential utilization of R. chinensis fruits as nutritional supplement and/or functional food to prevent or ameliorate diabetes.

The Protective Effect and Mechanism of a Phytochemical Extract from the Wild Vegetable Shutou (Crateva unilocularis Buch.) against Acetaminophen-Induced Liver Injury in Mice.

Acetaminophen (APAP) abuse is a common public health problem which can cause severe liver damage. However, strategies for dealing with this situation safely and effectively are very limited. The goal of the current work was to evaluate the protection and potential molecular mechanisms of an ethanol extract from shoots of the wild vegetable shutou (Crateva unilocularis Buch.) (ECS) against APAP-induced liver damage in mice. Mice orally received ECS for seven days (300 or 600 mg/kg b.w. per day) before being intraperitoneally injected with APAP (250 mg/kg). Results exhibited that ECS obviously decreased the content of alkaline phosphatase, alanine aminotransferase, aspartate transaminase, and malondialdehyde (p < 0.05). Catalase and superoxide dismutase were notably restored (p < 0.05), and the content of reduced glutathione was obviously increased (p < 0.05). Moreover, ECS significantly inhibited the secretion of interleukin-1ß and tumor necrosis factor-α (p < 0.05). Further analyses of the mechanisms showed that ECS may alleviate oxidative stress in the liver by increasing the expression of the nuclear factor erythroid-2-related factor 2 and NADH quinone oxidoreductase 1 proteins, and may suppress liver inflammation by inhibiting the expression of the phosphorylated-inhibitor kappa B alpha/inhibitor kappa B alpha, phosphorylated-nuclear factor κB/nuclear factor κB, and cyclooxygenase-2 proteins. Meanwhile, ECS inhibited hepatocyte apoptosis by enhancing B-cell lymphoma gene 2 and suppressing Bcl-2-associated X protein. In summary, ECS may be used as a dietary supplement to prevent the liver damage caused by APAP abuse.

Composition, functional properties, health benefits and applications of oilseed proteins: A systematic review.

Common oilseeds, such as soybean, peanut, rapeseed, sunflower seed, sesame seed and chia seed, are key sources of edible vegetable oils. Their defatted meals are excellent natural sources of plant proteins that can meet consumers' demand for health and sustainable substitutes for animal proteins. Oilseed proteins and their derived peptides are also associated with many health benefits, including weight loss and reduced risks of diabetes, hypertension, metabolic syndrome and cardiovascular events. This review summarizes the current status of knowledge on the protein and amino acid composition of common oilseeds as well as the functional properties, nutrition, health benefits and food applications of oilseed protein. Currently, oilseeds are widely applied in the food industry regarding for their health benefits and good functional properties. However, most oilseed proteins are incomplete proteins and their functional properties are not promising compared to animal proteins. They are also limited in the food industry due to their off-flavor, allergenic and antinutritional factors. These properties can be improved by protein modification. Therefore, in order to make better use of oilseed proteins, methods for improving their nutrition value, bioactive activity, functional and sensory characteristics, as well as the strategies for reducing their allergenicity were also discussed in this paper. Finally, examples for the application of oilseed proteins in the food industry are presented. Limitations and future perspectives for developing oilseed proteins as food ingredients are also pointed out. This review aims to foster thinking and generate novel ideas for future research. It will also provide novel ideas and broad prospects for the application of oilseeds in the food industry.

Fabrication of anthocyanin-rich W1/O/W2 emulsion gels based on pectin-GDL complexes: 3D printing performance.

The stability of anthocyanin-rich W1/O/W2 double emulsions prepared with Nicandra physalodes (Linn.) Gaertn. Seeds pectin was investigated, including droplet sizes, ζ-potential, viscosity, color, microstructures and encapsulation efficiency. Furthermore, the gelation behavior, rheological behavior, texture behavior and three-dimensional (3D) printing effects of the W1/O/W2 emulsion gels induced with Glucono-delta-lactone (GDL) were studied. The L*, b*, ΔE, droplet sizes and ζ-potential of the emulsions were gradually increased, while other indicators were gradually decreased during 28 days of storage under 4 ℃. The storage stability of sample under storage at 4 ℃ was higher than 25 ℃. The G' of W1/O/W2 emulsion gels gradually boosted with increased GDL addition, and reached the highest after the addition of 1.6 % GDL. In creep-recovery sweep, the minimum strain of 1.68 % and the highest recovery rate of 86 % were also found for the emulsion gels with 1.6 % GDL. Accordingly, the models "KUST", hearts, flowers printed by emulsion gels after 60 min addition of 1.6 % GDL had the best printing effects. The W1/O/W2 emulsion gels based on pectin-GDL complexes exhibited good performance in protecting anthocyanins and suggested as a potential ink for food 3D printing.

Rhus chinensis Mill. fruits alleviate liver injury induced by isoniazid and rifampicin through regulating oxidative stress, apoptosis, and bile acid transport.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhus chinensis Mill. is a species of the genus Rhus belonging to the family Anacardiaceae. Its fruits used to treat/prevent liver related diseases (e.g., jaundice and hepatitis) in folk medicine. Otherwise, the effects and underlying mechanisms of the fruits on the prevention of isoniazid and rifampicin-caused liver injury have not been investigated. AIM OF THE STUDY: To study the preventive effects and mechanisms of the Rhus chinensis Mill. fruits on isoniazid and rifampicin-caused liver injury. MATERIALS AND METHODS: This experiment was based on rifampicin (75 mg/kg/day) and isoniazid (75 mg/kg/day)-induced liver damage model to explain the pharmacological effects of Rhus chinensis Mill. fruits. The prevention of the extract from Rhus chinensis Mill. fruits on isoniazid and rifampicin-caused liver injury were evaluated using biochemical parameters, histopathological analysis, and immunofluorescence technique. Apart from that, the potential molecular mechanisms were elucidated by analyzing the expression of such crucial proteins participated in oxidative stress, apoptosis, and bile acid transport. RESULTS: The extract from Rhus chinensis Mill. fruits significantly reduced the levels of ALT, AST, TBIL, ALP and MDA. Besides, the extract, especially 800 mg/kg b.w., was remarkably decreased the content of TNF-α,IL-6 and IL-1ß, restored the levels of GSH and SOD. The results of Western blot also presented that the extract could activate the Nrf2 protein pathway and inhibit the expression of CYP2E1 to reduce oxidative stress. Meanwhile, the extract significantly up-regulated the expressions of BSEP and Mrp2 to regulate the transport of bile acid, and alleviated the cellular apoptosis via adjusting the expression of Bax and Bcl-2 proteins. CONCLUSIONS: Rhus chinensis Mill. fruits can prevent the liver injury induced by isoniazid and rifampicin in mice through adjusting the expressions of multiple proteins in oxidative stress, apoptosis, and bile acid transport pathways. This paper may provide scientific basis for the fruits as a Chinese medicine to prevent/cure liver injury.

Secrets behind Protein Sequences: Unveiling the Potential Reasons for Varying Allergenicity Caused by Caseins from Cows, Goats, Camels, and Mares Based on Bioinformatics Analyses.

This study systematically investigated the differences in allergenicity of casein in cow milk (CM), goat milk (GM), camel milk (CAM), and mare milk (MM) from protein structures using bioinformatics. Primary structure sequence analysis reveals high sequence similarity between the α-casein of CM and GM, while all allergenic subtypes are likely to have good hydrophilicity and thermal stability. By analyzing linear B-cell epitope, T-cell epitope, and allergenic peptides, the strongest casein allergenicity is observed for CM, followed by GM, and the casein of MM has the weakest allergenicity. Meanwhile, 7, 9, and 16 similar or identical amino acid fragments in linear B-cell epitopes, T-cell epitopes, and allergenic peptides, respectively, were observed in different milks. Among these, the same T-cell epitope FLGAEVQNQ was shared by κ-CN in all four different species' milk. Epitope results may provide targets of allergenic fragments for reducing milk allergenicity through physical or/and chemical methods. This study explained the underlying secrets for the high allergenicity of CM to some extent from the perspective of casein and provided new insights for the dairy industry to reduce milk allergy. Furthermore, it provides a new idea and method for comparing the allergenicity of homologous proteins from different species.

The preventive effect of Chinese sumac fruit against monosodium urate-induced gouty arthritis in rats by regulating several inflammatory pathways.

Chinese sumac (Rhus chinensis Mill.) fruit is a traditional Chinese medicinal material that can be consumed daily. This study aimed to investigate whether the ethanol extract of sumac fruits can ameliorate monosodium urate-induced gouty arthritis in rats from the perspective of inflammation. Results showed that the extract of Chinese sumac fruits can obviously prevent monosodium urate-induced gouty arthritis in rats. Further analyses revealed that this bioactivity may be mainly achieved by modulating several inflammatory pathways, including NLRP3, NF-κB, and MAPK pathways. In addition, the extract can also improve oxidative stress by reducing the levels of malondialdehyde and myeloperoxidase, increasing the contents of superoxide dismutase and glutathione. In conclusion, this study revealed that the Chinese sumac fruit can alleviate the pathological symptoms of gouty arthritis by inhibiting inflammatory responses and oxidative stress, which can provide a theoretical basis for the use of Chinese sumac fruits as a Chinese herbal medicine and health food for the prevention and treatment of gouty arthritis.

Advance in dietary polyphenols as dipeptidyl peptidase-IV inhibitors to alleviate type 2 diabetes mellitus: aspects from structure-activity relationship and characterization methods.

Dietary polyphenols with great antidiabetic effects are the most abundant components in edible products. Dietary polyphenols have attracted attention as dipeptidyl peptidase-IV (DPP-IV) inhibitors and indirectly improve insulin secretion. The DPP-IV inhibitory activities of dietary polyphenols depend on their structural diversity. Screening methods that can be used to rapidly and accurately identify potential polyphenol DPP-IV inhibitors are urgently needed. This review focuses on the relationship between the structures of dietary polyphenols and their DPP-IV inhibitory effects. Different characterization methods used for polyphenols as DPP-IV inhibitors have been summarized and compared. We conclude that the position and number of hydroxyl groups, methoxy groups, glycosylated groups, and the extent of conjugation influence the efficiency of inhibition of DPP-IV. Various combinations of methods, such as in-vitro enzymatic inhibition, ex-vivo/in-vivo enzymatic inhibition, cell-based in situ, and in-silico virtual screening, are used to evaluate the DPP-IV inhibitory effects of dietary polyphenols. Further investigations of polyphenol DPP-IV inhibitors will improve the bioaccessibility and bioavailability of these bioactive compounds. Exploration of (i) dietary polyphenols derived from multiple targets, that can prevent diabetes, and (ii) actual binding interactions via multispectral analysis, to understand the binding interactions in the complexes, is required.