Characterization of binding interactions of (-)-epigallocatechin-3-gallate from green tea and lipase

Epigallocatechin-3-gallate attenuates the sulfamethoxazole-induced immunotoxicity and reduces SMZ residues in Procambarus clarkii

Sulfamethoxazole (SMZ) is a commonly used antibiotic in aquaculture, and its residues in water bodies pose a significant threat to aquatic organisms in the water environment. In the present study, epigallocatechin-3-gallate (EGCG), a catecholamine, was used to mitigate the immunotoxicity caused by SMZ exposure in Procambarus clarkii. EGCG reduced the apoptosis rate, which was elevated by SMZ exposure, and increased the total hemocyte count. Simultaneously, EGCG enhanced the activities of enzymes related to antibacterial and antioxidant activities, such as superoxide dismutase (SOD), catalase (CAT), lysozyme (LZM), acid phosphatase (ACP), and GSH, which were decreased following SMZ exposure. Hepatopancreatic histology confirmed that EGCG ameliorated SMZ-induced tissue damage caused by SMZ exposure. In addition to EGCG attenuating SMZ-induced immunotoxicity in crayfish, we determined that EGCG can effectively reduce SMZ residues in crayfish exposed to SMZ. In addition, at the genetic level, the expression levels of genes related to the immune response in hemocytes were disrupted after SMZ exposure, and EGCG promoted their recovery and stimulated an increase in the expression levels of metabolism-related transcripts in hemocytes. The transcriptome analysis was conducted, and "phagosome" and "apoptosis" pathways were shown to be highlighted using Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses. To the best of our knowledge, this is the first study to confirm that EGCG attenuates SMZ-induced immunotoxicity in aquatic animals and reduces SMZ residues in aquatic animals exposed to SMZ. Our study contributes to the understanding of the mechanisms by which EGCG reduces the immunotoxicity of antibiotic residues in aquatic animals.

Differential effects of theasinensins and epigallocatechin-3-O-gallate on phospholipid bilayer structure and liposomal aggregation

(-)-Epigallocatechin-3-O-gallate (EGCg), the major catechin responsible for the health-enhancing and disease-preventive effects of green tea, is susceptible to auto-oxidation at physiological pH levels. However, whether the oxidized EGCg resulting from its oral consumption possesses any bioactive functions remains unclear. This study presents a differential analysis of intact and oxidized EGCg regarding their interactions with phosphatidylcholine liposomes, serving as a simple biomembrane model. In the presence of ascorbic acid, pre-oxidized EGCg induced liposomal aggregation in a dose-dependent manner, whereas intact EGCg did not. Toxicity evaluation using calcein-loaded liposomes revealed that liposomal aggregation is associated with minimal membrane damage. Through fractionation of the oxidized EGCg sample, the fraction containing theasinensins showed high liposomal aggregation activity. Overall, these results suggest that oxidatively condensed EGCg dimers may stimulate various cells by altering the plasma membrane in a manner different from that of EGCg monomers.

Conformational dynamics of trypsin in the presence of caffeic acid: a spectroscopic and computational investigation

Caffeic acid is one of the widely distributed phenolic compounds in nature and can be found in planet products. On the other hand, trypsin is a vital digestive enzyme in the intestine that plays an essential role in the immune response, blood coagulation, apoptosis and protein maturation like protein digestion. Several studies have revealed the inhibitory effects of the phenolic compound on the digestive enzyme. The present study reports functional and conformational alteration of trypsin after caffeic acid addition using multiple experimental and computational techniques for the first time. The intrinsic fluorescence of trypsin is quenched in the presence of caffeic acid via a static mechanism. The percent of secondary structures (α-helix and β-sheet) of trypsin alter after caffeic acid addition. In the kinetic study, a reduction in the trypsin function is obtained with a lower Vmax and Kcat upon interaction with caffeic acid. The thermal study reveals an unstable structure of trypsin upon complex formation with this phenolic compound. Also, the binding sites and conformational changes of trypsin are elucidated through molecular docking and molecular dynamic simulation.Communicated by Ramaswamy H. Sarma.

Unleashing the binding interaction of chrysin-Cu(II) complex with the biomacromolecular targets: further studies of cell cytotoxicity and radical scavenging properties

Flavonoids are significant dietary components and have ability to coordinate with metal ions to produce novel drug discovery leads that are superior to those of the parent flavonoids. Here, in this report, we have synthesized chrysin-Cu(II) complex (as per reported article) and characterized it further with different analytical techniques. The synthesized complex was evaluated for radical scavenging and cell cytotoxicity studies where it exhibited enhanced activity as compared to bare chrysin. The interaction studies of the complex with ct-DNA (Kb ⁓ 105 M-1), human serum albumin (HSA) and ovalbumin (Kb ⁓ 104 M-1) were evaluated using multi-spectroscopic and molecular docking studies. Groove binding mode with ct-DNA was observed as confirmed from competitive displacement studies, viscosity measurement, melting temperature estimation and docking analyses. The complex exhibited comparatively higher affinity towards ct-DNA which indicated it efficient transportation by the carrier proteins and controlled release in the target DNA.Communicated by Ramaswamy H. Sarma.

Effects of Covalent or Noncovalent Binding of Different Polyphenols to Acid-Soluble Collagen on Protein Structure, Functionality, and Digestibility

In this study, the structure, function, and digestibility of noncovalent complexes and covalent conjugates formed by acid-soluble collagen with polyphenols of different structures (quercetin, epicatechin, gallic acid, chlorogenic acid, procyanidin, and tannic acid) were investigated. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that polyphenols were covalently bound to collagen by laccase catalytic oxidation. Biolayer interferometry revealed that the noncovalent binding strength of polyphenols to collagen from high to low was quercetin > gallic acid > chlorogenic acid > epicatechin, which was consistent with the trend of covalent polyphenol binding. Procyanidin and tannic acid had strong noncovalent binding, but their covalent binding ability was weak. Compared with the pure collagen, the complexes improved emulsification and antioxidant properties (more than 2.5 times), and the conjugates exhibited better thermal stability (99.4-106.8 °C) and antidigestion ability (reduced by more than 37%). The finding sheds new light on the use of collagen as a functional food ingredient in the food industry.

Research of Multicopper Oxidase and Its Degradation of Histamine in Lactiplantibacillus plantarum LPZN19

In order to explore the structural changes and products of histamine degradation by multicopper oxidase (MCO) in Lactiplantibacillus plantarum LPZN19, a 1500 bp MCO gene in L. plantarum LPZN19 was cloned, and the recombinant MCO was expressed in E. coli BL21 (DE3). After purification by Ni2+-NTA affinity chromatography, the obtained MCO has a molecular weight of 58 kDa, and it also has the highest enzyme activity at 50 °C and pH 3.5, with a relative enzyme activity of 100%, and it maintains 57.71% of the relative enzyme activity at 5% salt concentration. The secondary structure of MCO was determined by circular dichroism, in which the proportions of the α-helix, β-sheet, β-turn and random coil were 2.9%, 39.7%, 21.2% and 36.1%, respectively. The 6xj0.1.A with a credibility of 68.21% was selected as the template to predict the tertiary structure of MCO in L. plantarum LPZN19, and the results indicated that the main components of the tertiary structure of MCO were formed by the further coiling and folding of a random coil and β-sheet. Histamine could change the spatial structure of MCO by increasing the content of the α-helix and β-sheet. Finally, the LC-MS/MS identification results suggest that the histamine was degraded into imidazole acetaldehyde, hydrogen peroxide and ammonia.

Hyperoside inhibits pancreatic lipase activity in vitro and reduces fat accumulation in vivo

Hyperoside, the main component of many anti-obesity plants, might exhibit a lipase inhibition effect to reduce fat accumulation. The anti-obesity effect of hyperoside was investigated by studying its inhibitory effect and mechanism on pancreatic lipase in vitro and evaluating its ability to reduce lipid accumulation in vivo. Hyperoside is a mixed-type inhibitor of lipase with an IC₅₀ of 0.67 ± 0.02 mmol L^-in vitro. Hyperoside changed the secondary conformation of lipase, increased the α-helix content, and changed the microenvironment of lipase through static quenching. The interaction between hyperoside and lipase results from a strong binding spontaneous exothermic reaction, mainly through hydrogen bonding, van der Waals force and electrostatic force. Hyperoside protected hepatic lipid accumulation and adipose tissue hypertrophy and reduced the expression of inflammatory factors in high-fat diet-induced rats. Moreover, hyperoside had a good inhibitory effect on lipase activity in serum and increased fecal fat excretion, thereby reducing lipid absorption in vivo. This study provides theoretical support for the research and development of hyperoside in fat-reducing functional foods.

Ultrasonic-assisted enzymatic improvement of polyphenol content, antioxidant potential, and in vitro inhibitory effect on digestive enzymes of Miang extracts

The aims of this research were to optimize the ultrasonic-assisted enzymatic extraction of polyphenols under Miang and tannase treatment conditions for the improvement of antioxidant activity of Miang extracts via response surface methodology. Miang extracts treated with and without tannase were investigated for their inhibitory effects on digestive enzymes. The optimal conditions for ultrasonic-assisted enzymatic extraction of the highest total polyphenol (TP) (136.91 mg GAE/g dw) and total flavonoid (TF) (5.38 mg QE/g dw) contents were as follows: 1 U/g cellulase, 1 U/g xylanase, 1 U/g pectinase, temperature (74 °C), and time (45 min). The antioxidant activity of this extract was enhanced by the addition of tannase obtained from Sporidiobolus ruineniae A45.2 undergoing ultrasonic treatment and under optimal conditions (360 mU/g dw, 51 °C for 25 min). The ultrasonic-assisted enzymatic extraction selectively promoted the extraction of gallated catechins from Miang. Tannase treatment improved the ABTS and DPPH radical scavenging activities of untreated Miang extracts by 1.3 times. The treated Miang extracts possessed higher IC₅₀ values for porcine pancreatic α-amylase inhibitory activity than those that were untreated. However, it expressed approximately 3 times lower IC₅₀ values for porcine pancreatic lipase (PPL) inhibitory activity indicating a marked improvement in inhibitory activity. The molecular docking results support the contention that epigallocatechin, epicatechin, and catechin obtained via the biotransformation of the Miang extracts played a crucial role in the inhibitory activity of PPL. Overall, the tannase treated Miang extract could serve as a functional food and beneficial ingredient in medicinal products developed for obesity prevention.

Deciphering the interactions of phytochemicals with ovalbumin, the major food allergen from egg white: spectroscopic and computational studies

Ovalbumin (OVA), the major component of egg white, has been used as a model carrier protein to study the interaction of four bioactive phytochemicals 6-hydroxyflavone, chrysin, naringin, and naringenin. A static quenching mechanism was primarily associated with the complexation of the flavonoids with OVA. Hydrophobic forces play a major part in the stability of the complexes. The structural changes within the protein in response to flavonoid binding revealed a decrease in OVA's α-helical content. The hypothesized binding site for flavonoids in OVA overlaps with one or more immunoglobulin E-binding epitopes that may have some effect in the immunoglobulin E response pathway. The flavonoids remain in the same binding site throughout the simulation time and impart protein stability by forming different noncovalent interactions. This study presents comprehensive information about the interaction of the flavonoids with OVA and the associated structural variations after the binding, which might help researchers better comprehend similar medication pharmacodynamics and provide critical information for future therapeutic development.

Impact of internal aqueous phase gelation on in vitro lipid digestion of epigallocatechin gallate-loaded W1 /O/W2 double emulsions incorporated in alginate hydrogel beads

Our objective was to investigate if the internal aqueous phase gelation of Water-in-oil-in-water double emulsions encapsulated in alginate beads would affect their structural stability and lipid hydrolysis during in vitro digestion. Therefore, bioactive molecules such as (-)-epigallocatechin gallate were encapsulated into different types of delivery systems: original double emulsions (as control) and incorporated double emulsions (filled in alginate hydrogel beads), both with non-gelled or gelled internal aqueous phase by locust bean gum and κ-carrageenan. After 2 h of gastric digestion, the gelled original emulsions showed smaller mean droplet diameters and less coalescence during the in vitro simulated gastrointestinal digestion compared to the non-gelled original emulsions. For the incorporated emulsions, oil droplets released from beads aggregated under intestinal conditions, and the rate of lipolysis was delayed. Interestingly, the internal aqueous phase gelation also impacted the rate and cumulative amount of free fatty acids (FFA) released. PRACTICAL APPLICATION: The combination of incorporating (-)-epigallocatechin gallate-loaded double emulsions into the alginate hydrogel matrix and gelling the internal aqueous phase was a benefit to regulating the rate and extent of lipid digestion for specific applications in foods, such as to control blood lipid levels and appetite.

Research on interaction regularities and mechanisms between lactic acid and aroma compounds of Baijiu

This study investigated the interactions between lactic acid (LA) and odorants of Baijiu using headspace solid phase microextraction with gas chromatography-mass spectrometry (HS-SPME-GC-MS), ultraviolet absorption spectroscopy (UV) and nuclear magnetic resonance (NMR). The HS-SPME-GC-MS analysis results showed that LA promoted the volatilities of most of low boiling acids, esters, alcohols, aldehydes and ketones, especially short-chain branched esters were promoted by 41-49%. In contrast, LA suppressed the volatilities of most aromatic compounds. UV spectroscopy, thermodynamic analysis, and NMR combined with theoretical calculations further revealed that the interactions between LA and 4-ethyl-2-methoxyphenol (4-EP), 2-methoxy-4-methylphenol (2-MP) and 1-butanol were dominated by van der Waals forces and supplemented by electrostatic interactions, which included hydrogen bonds formed between the carboxyl group in LA and the hydroxyl and methoxy groups in 4-EP or 2-MP and π-hydrogen bonds between the hydrogen of the carboxyl group of LA and the benzene ring of 4-EP or 2-MP.

DeepBindBC: a practical deep learning method for identifying native-like protein-ligand complexes in virtual screening

Identifying native-like protein-ligand complexes (PLCs) from an abundance of docking decoys is critical for large-scale virtual drug screening in early-stage drug discovery lead searching efforts. Providing reliable prediction is still a challenge for most current affinity predicting models because of a lack of non-binding data during model training, lost critical physical-chemical features, and difficulties in learning abstract information with limited neural layers. In this work, we proposed a deep learning model, DeepBindBC, for classifying putative ligands as binding or non-binding. Our model incorporates information on non-binding interactions, making it more suitable for real applications. ResNet model architecture and more detailed atom type representation guarantee implicit features can be learned more accurately. Here, we show that DeepBindBC outperforms Autodock Vina, Pafnucy, and DLSCORE for three DUD.E testing sets. Moreover, DeepBindBC identified a novel human pancreatic α-amylase binder validated by a fluorescence spectral experiment (K_a= 1.0×10⁵ M). Furthermore, DeepBindBC can be used as a core component of a hybrid virtual screening pipeline that incorporating many other complementary methods, such as DFCNN, Autodock Vina docking, and pocket molecular dynamics simulation. Additionally, an online web server based on the model is available at http://cbblab.siat.ac.cn/DeepBindBC/index.php for the user's convenience. Our model and the web server provide alternative tools in the early steps of drug discovery by providing accurate identification of native-like PLCs.

Screening of Anti-Lipase Components of Artemisia argyi Leaves Based on Spectrum-Effect Relationships and HPLC-MS/MS

Pancreatic lipase is a key lipase for triacylglyceride digestion and absorption, which is recognized as a promising target for treatment of metabolic disorders. Natural phytochemicals are hopeful sources for pancreatic lipase inhibitors. The leaves of Artemisia argyi H.Lév. and Vaniot (AL) is commonly used as herbal medicine or food supplement in China and other Asian countries for hundreds of years. AL mainly contains essential oils, phenolic acids, flavonoids and terpenoids, which exhibit many pharmacological activities such as antioxidant, anti-inflammatory, antimicrobial, analgetic, anti-cancer, anti-diabetes and immunomodulatory effects. However, the anti-lipase activity of AL was lack of study and the investigation of anti-lipase ingredients from AL was also insufficient. In the present study, the anti-lipase activity of AL was evaluated in vitro and the potentially pancreatic lipase inhibitors of AL were investigated. High performance liquid chromatography was used to establish fingerprints of AL samples, and fifteen peaks were selected. The anti-lipase activities of AL samples were evaluated by a pancreatic lipase inhibition assay. Then, the spectrum-effect relationships between fingerprints and pancreatic lipase inhibitory activities were investigated to identify the anti-lipase constitutes in AL. As the results, four caffeoylquinic acids, which were identified as neochlorogenic acid, chlorogenic acid, isochlorogenic acid B, and isochlorogenic acid A by high performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry, were selected as potential pancreatic lipase inhibitors in AL. Moreover, anti-lipase activity assessment and molecular docking study of the four compounds were performed to validate the potential lipase inhibitors in AL. The results revealed that the four caffeoylquinic acids in AL as bioactive compounds displayed with anti-lipase activity. The present research provided evidences for the anti-lipase activity of AL, and suggested that some bioactive compounds in AL could be used as lead compounds for discovering of new pancreatic lipase inhibitors.

Investigation of lipase-ligand interactions in porcine pancreatic extracts by microscale thermophoresis

The evaluation of binding affinities between large biomolecules and small ligands is challenging and requires highly sensitive techniques. Microscale thermophoresis (MST) is an emerging biophysical technique used to overcome this limitation. This work describes the first MST binding method to evaluate binding affinities of small ligands to lipases from crude porcine pancreatic extracts. The conditions of the MST assay were thoroughly optimized to successfully evaluate the dissociation constant (K_d) between pancreatic lipases (PL) and triterpenoid compounds purified from oakwood. More precisely, the fluorescent labeling of PL (PL*) using RED-NHS dye was achieved via a buffer exchange procedure. The MST buffer was composed of 20 mM NaH₂PO₄ + 77 mM NaCl (pH 6.6) with 0.05% Triton-X added to efficiently prevent protein aggregation and adsorption, even when using only standard, uncoated MST capillaries. Storage at -20 °C ensured stability of PL* and its fluorescent signal. MST results showed that crude pancreatic extracts were suitable as a source of PL for the evaluation of binding affinities of small ligands. Quercotriterpenoside-I (QTT-I) demonstrated high PL* binding affinity (31 nM) followed by 3-O-galloylbarrinic acid (3-GBA) (500 nM) and bartogenic acid (BA) (1327 nM). To enrich the 50 kDa lipase responsible for the majority of hydrolysis activity in the crude pancreatic extracts, ammonium sulfate precipitation was attempted and its efficiency confirmed using capillary electrophoresis (CE)-based activity assays and HRMS. Moreover, to accurately explain enzyme modulation mechanism, it is imperative to complement binding assays with catalytic activity ones.

Gliadin Sequestration as a Novel Therapy for Celiac Disease: A Prospective Application for Polyphenols

Celiac disease is an autoimmune disorder characterized by a heightened immune response to gluten proteins in the diet, leading to gastrointestinal symptoms and mucosal damage localized to the small intestine. Despite its prevalence, the only treatment currently available for celiac disease is complete avoidance of gluten proteins in the diet. Ongoing clinical trials have focused on targeting the immune response or gluten proteins through methods such as immunosuppression, enhanced protein degradation and protein sequestration. Recent studies suggest that polyphenols may elicit protective effects within the celiac disease milieu by disrupting the enzymatic hydrolysis of gluten proteins, sequestering gluten proteins from recognition by critical receptors in pathogenesis and exerting anti-inflammatory effects on the system as a whole. This review highlights mechanisms by which polyphenols can protect against celiac disease, takes a critical look at recent works and outlines future applications for this potential treatment method.

Anion carboxymethylated β-glucan alleviates undesirable binding between procyanidins and β-galactosidase

To solve the potential problem of hindered β-galactosidase activity by procyanidins, carboxymethylated Pachyman (CMP), a negatively-charged carboxymethylated (1 → 3)-β-d-glucan, was applied to mitigate inhibition by procyanidins. The mechanisms underlying this effect were explored through enzyme kinetic analysis, fluorescence quenching assays, circular dichroism, and molecular docking studies. The results indicated that the introduction of CMP could decrease the inhibition rate of high-concentration lotus seedpod oligomeric procyanidins (LSOPC) from 98.7 to 46.5%, and enabled low-concentration LSOPC to activate β-galactosidase in vitro and in vivo. The competitive/noncompetitive inhibition constants, fluorescence quenching constants, and molecular docking results indicated that the mechanism of this effect might be CMP competing with β-galactosidase to bind procyanidins, resulting in restoration of the catalytic centre and key active site of procyanidin-bound lactase. Additionally, it was affected by procyanidin-CMP noncovalent interactions. This study illustrates a promising strategy for mitigating the anti-nutritional properties of procyanidins and activating β-galactosidase to promote intestinal health.

Epigallocatechin-3-gallate ameliorates glucolipid metabolism and oxidative stress in type 2 diabetic rats

AIMS

The objective of this study was to explore the effects of epigallocatechin-3-gallate (EGCG) on type 2 diabetes mellitus (T2DM).

MAIN METHODS

Male Sprague-Dawley rats were allocated into six groups. The control group received a conventional diet. The diabetic group received a high-sucrose high-fat (HSHF) diet for 4 weeks and then was fasted and injected with streptozotocin (STZ); subsequently, the rats received a HSHF diet for another 4 weeks to develop diabetes. The four treatment groups were diabetic rats that received intragastric metformin (500 mg/kg/day) or EGCG (25, 50, and 100 mg/kg/day) for 10 weeks. All groups except the control group received a HSHF diet throughout the experiment. Several biochemical parameters such as fasting blood glucose (FBG), postprandial blood glucose (PBG), liver glycogen, muscle glycogen, fasting serum insulin (FSI), homeostasis model of insulin resistance (HOMA-IR), total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), free fatty acids (FFA), superoxide dismutase (SOD), and malondialdehyde (MDA) were measured to assess the effects of EGCG on glycemic control, insulin resistance, lipid profile, and oxidative stress. Furthermore, oxidative stress in pancreatic islet β cells was detected by dihydroethidium staining.

KEY FINDINGS

A HSHF diet and STZ injection induced T2DM, as indicated by changed blood glucose and body weight, which was accompanied by insulin resistance, an altered lipid profile, and oxidative stress. Interestingly, EGCG treatment dose-dependently recovered these indexes.

SIGNIFICANCE

EGCG successfully ameliorated glycemic control and insulin sensitivity while reducing the lipid profile and oxidative stress in a T2DM rat model.

Evaluation inhibitory activity of catechins on trypsin by capillary electrophoresis-based immobilized enzyme microreactor with chromogenic substrate

In this study, a capillary electrophoresis-based online immobilized enzyme microreactor was developed for evaluating the inhibitory activity of green tea catechins and tea polyphenol extracts on trypsin. The immobilized trypsin activity and other kinetic parameters were evaluated by measuring the peak area of the hydrolyzate of chromogenic substrate S-2765. The results indicated that the activity of the immobilized trypsin remained approximately 90.0% of the initial immobilized enzyme activity after 30 runs. The value of Michaelis-Menten constant (K_m ) was (0.47 ± 0.08) mM, and the half-maximal inhibitory concentration (IC₅₀ ) and inhibition constant (K_i ) of benzamidine were measured as 3.34 and 3.00 mM, respectively. Then, the inhibitory activity of four main catechins (epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate) and three tea polyphenol extracts (green tea, white tea, and black tea) on trypsin were investigated. The results showed that four catechins and three tea polyphenol extracts had potential trypsin inhibitory activity. In addition, molecular docking results illustrated that epigallocatechin gallate, epicatechin gallate, epicatechin, and epigallocatechin were all located not only in the catalytic cavity, but also in the substrate-binding pocket of trypsin. These results indicated that the developed method is an effective tool for evaluating inhibitory activity of catechins on trypsin.

Interaction of quercetin and epigallocatechin gallate (EGCG) aggregates with pancreatic lipase under simplified intestinal conditions

Diets rich in flavonoids have been related with low obesity rates, which could be related with their potential to inhibit pancreatic lipase, the main enzyme of fat assimilation. Some flavonoids can aggregate in aqueous medium suggesting that the inhibition mechanism could occur on both molecular and colloidal levels. This study investigates the interaction of two flavonoid aggregates, quercetin and epigallocatechin gallate (EGCG), with pancreatic lipase under simplified intestinal conditions. The stability and the morphology of these flavonoid aggregates were studied in four different solutions: Control (water), salt, low lipase concentration and high lipase concentration. Particles were found by optical microscopy in almost all the solutions tested, except EGCG-control. The results show that the precipitation rate decreases for quercetin and increases for EGCG in salt solution and that lipase stabilize quercetin aggregates. In addition, both flavonoids were shown to precipitate together with pancreatic lipase resulting in a sequestering of the enzyme.

Computational approaches for the discovery of natural pancreatic lipase inhibitors as antiobesity agents

Obesity is becoming one of the greatest threats to global health in the 21st century and therefore the development of novel antiobesity drugs is one of the top priorities of global drug research. An important treatment strategy includes the reduction of intestinal fat absorption through the inhibition of pancreatic lipase (PL). Natural products provide a vast pool of PL inhibitors with novel scaffolds that can possibly be developed into clinical products. Computational drug design methods have become increasingly invaluable in the drug discovery process. In recent years, the discovery of new antiobesity PL inhibitors has been facilitated by the application of computational methods. This review highlights some computer-aided drug design techniques utilized in the discovery of natural PL inhibitors.

Inhibitory characteristics of flavonol-3-O-glycosides from Polygonum aviculare L. (common knotgrass) against porcine pancreatic lipase

Pancreatic lipase (PL) is an enzyme that plays an essential role in the digestion of dietary lipids and is a suitable target for an anti-obesity dietary supplement. The objective of this study was to find a novel source of PL inhibitors from Korean medicinal plants and investigate the PL-inhibitory properties of the active constituents. From among 34 kinds of methanolic crude extracts, Polygonum aviculare L. showed the highest PL-inhibitory activity (63.97 ± 0.05% of inhibition). Solvent fractionation and liquid chromatography/mass spectrometry (LC/MS) analysis identified flavonol-3-O-glycosides, flavonol-3-O-(2″-galloyl)-glycosides, and flavonol aglycones as active constituents. Furthermore, the inhibitory characteristics of the major compounds were investigated in terms of enzyme kinetics and fluorescence quenching. The results suggested that the inhibitory activity of the major compounds is closely related to the tertiary structural change in PL, and that differences in inhibitory activity occurred due to slight discrepancies in their chemical structure.

Calorimetric approach for comparison of Angiopoietin-like protein 4 with other pancreatic lipase inhibitors

Pancreatic lipase (PNLIP) is a digestive enzyme that is a potential drug target for the treatment of obesity. A better understanding of its regulation mechanisms would facilitate the development of new therapeutics. Recent studies indicate that intestinal lipolysis by PNLIP is reduced by Angiopoietin-like protein 4 (ANGPTL4), whose N-terminal domain (nANGPTL4) is a known inactivator of lipoprotein lipase (LPL) in blood circulation and adipocytes. To elucidate the mechanism of PNLIP inhibition by ANGPTL4, we developed a novel approach, using isothermal titration calorimetry (ITC). The obtained results were compared with those of well-described inhibitors of PNLIP - ε-polylysine (EPL), (-)-epigallocatechin-3-gallate (EGCG) and tetrahydrolipstatin. We demonstrate that ITC allows to investigate PNLIP inhibition mechanisms in complex substrate emulsions and that the ITC-based assay is highly sensitive - the lowest concentration for quantification of PNLIP is 1.5 pM. Combining ITC with surface plasmon resonance and fluorescence measurements, we present evidence that ANGPTL4 is a lipid-binding protein that influences PNLIP activity through interactions with components of substrate emulsions (bile salts, phospholipids and triglycerides), and this promotes the aggregation of triglyceride emulsions similarly to the PNLIP inhibitors EPL and EGCG. In the absence of substrate emulsion, unlike in the case of LPL, ANGPTL4 did not induce the inactivation of PNLIP. Our data also prove that due to various interactions with components of substrate systems, the effect of a PNLIP inhibitor depends on whether its effect is measured in a complex substrate emulsion or in a simple substrate system.

Mechanism of binding interactions between young apple polyphenols and porcine pancreatic α-amylase

The binding interactions between young apple polyphenols and porcine pancreatic α-amylase were investigated through isothermal titration calorimetry (ITC), differential scanning calorimetry (DSC) and molecular docking. The results obtained were compared with those obtained through inhibition kinetics and fluorescence quenching. It was found that binding of tannic acid, chlorogenic acid, caffeic acid and epicatechin with α-amylase is an exothermal process, with the binding constants in the order of tannic acid > chlorogenic acid > caffeic acid > epicatechin. This is consistent with the orders of reciprocal of competitive inhibition constant and fluorescence quenching constant. The binding energy obtained through molecular docking showed the same order, except for epicatechin. These results are consistent with the inhibition of α-amylase being caused by the binding of the polyphenols with the enzyme. In addition, from the fluorescence quenching and DSC data, total polyphenols, tannic acid, chlorogenic acid and caffeic acid were found to partially unfold the enzyme structure.

Salvia hispanica L. (chia) seeds oil extracts reduce lipid accumulation and produce stress resistance in Caenorhabditis elegans

Background

Salvia hispanica seeds have been commonly used by people that seek healthy habits through natural foods to reduce cholesterol and triacylglycerides levels, however, the evidences that support this assumption are still scarce in literature. Here, we aimed to evaluate the lipid lowering effects of chia by using Caenorhabditis elegans as animal model, a nematode that has proven its usefulness for lipid metabolism studies.

Methods

We prepared hexane (HE) and Bligh-Dyer (BDE) extracts, evaluated and compared their safety, antioxidant potential and their lipid-lowering activity in the worms.

Results

The characterization of both extracts demonstrated that there were no differences in their lipid composition; however, BDE depicted better antioxidant potential. Both extracts reduced worm’s survival from 2%, and reproduction was reduced following treatment with both extracts, though a more notable effect was observed in HE-treated worms. In addition, the non-toxic concentration of both extracts (1%) increased stress resistance against paraquat toxicity in an antidote paradigm. Notably, this same concentration of both extracts reduced lipid accumulation in obese worms, which was not caused by food deprivation.

Conclusions

Taken together, our data demonstrate that both extraction methods from chia seeds result in oils that are rich in mono and polyunsaturated fatty acids, which may modulate lipid accumulation and provide antioxidant resistance in C. elegans.

Antiviral Mechanism of Action of Epigallocatechin-3-O-gallate and Its Fatty Acid Esters

Epigallocatechin-3-O-gallate (EGCG) is the major catechin component of green tea (Cameria sinensis), and is known to possess antiviral activities against a wide range of DNA viruses and RNA viruses. However, few studies have examined chemical modifications of EGCG in terms of enhanced antiviral efficacy. This paper discusses which steps of virus infection EGCG interferes with, citing previous reports. EGCG appears most likely to inhibits the early stage of infections, such as attachment, entry, and membrane fusion, by interfering with viral membrane proteins. According to the relationships between structure and antiviral activity of catechin derivatives, the 3-galloyl and 5'-OH group of catechin derivatives appear critical to antiviral activities. Enhancing the binding affinity of EGCG to virus particles would thus be important to increase virucidal activity. We propose a newly developed EGCG-fatty acid derivative in which the fatty acid on the phenolic hydroxyl group would be expected to increase viral and cellular membrane permeability. EGCG-fatty acid monoesters showed improved antiviral activities against different types of viruses, probably due to their increased affinity for virus and cellular membranes. Our study promotes the application of EGCG-fatty acid derivatives for the prevention and treatment of viral infections.

Inhibitory Effect of Persimmon Tannin on Pancreatic Lipase and the Underlying Mechanism in Vitro

Pancreatic lipase (PL) is a critical enzyme associated with hyperlipidemia and obesity. A previous study of ours suggested that persimmon tannin (PT) was the main component accounting for the antihyperlipidemic effects of persimmon fruits, but the underlying mechanisms were unclear. In this present study, the inhibitory effect of PT on PL was studied and the possible mechanisms were evaluated by fluorescence spectroscopy, circular dichroism (CD) spectra, isothermal titration calorimetry (ITC), and molecular docking. PT had a high affinity to PL and inhibited the activity of PL with the half maximal inhibitory concertation (IC₅₀) value of 0.44 mg/mL in a noncompetitive way. Furthermore, molecular docking revealed that the hydrogen bonding and π-π stacking was mainly responsible for the interaction. The strong inhibition of PT on PL in the gastrointestinal tract might be one mechanism for its lipid-lowering effect.

In Vitro and In Silico Studies of the Molecular Interactions of Epigallocatechin-3-O-gallate (EGCG) with Proteins That Explain the Health Benefits of Green Tea

Green tea has been shown to have beneficial effects on many diseases such as cancer, obesity, inflammatory diseases, and neurodegenerative disorders. The major green tea component, epigallocatechin-3-O-gallate (EGCG), has been demonstrated to contribute to these effects through its anti-oxidative and pro-oxidative properties. Furthermore, several lines of evidence have indicated that the binding affinity of EGCG to specific proteins may explain its mechanism of action. This review article aims to reveal how EGCG-protein interactions can explain the mechanism by which green tea/EGCG can exhibit health beneficial effects. We conducted a literature search, using mainly the PubMed database. The results showed that several methods such as dot assays, affinity gel chromatography, surface plasmon resonance, computational docking analyses, and X-ray crystallography have been used for this purpose. These studies have provided evidence to show how EGCG can fit or occupy the position in or near functional sites and induce a conformational change, including a quaternary conformational change in some cases. Active site blocking, steric hindrance by binding of EGCG near an active site or induced conformational change appeared to cause inhibition of enzymatic activity and other biological activities of proteins, which are related to EGCG’s biological oligomer and formation of their toxic aggregates, leading to the prevention of neurodegenerative diseases and amyloidosis. In conclusion, these studies have provided useful information on the action of green tea/catechins and would lead to future studies that will provide further evidence for rational EGCG therapy and use EGCG as a lead compound for drug design.

Evaluation of anti-lipase activity and bioactive flavonoids in the Citri Reticulatae Pericarpium from different harvest time

BACKGROUND

Inhibition of pancreatic lipase is an attractive approach to the treatment of obesity and other metabolic disorders. Naturally occurring phytochemicals are promising sources of lipase inhibitors.

PURPOSE

In the present study, the anti-lipase activity of Citri Reticulatae Pericarpium (CRP) extracts was firstly evaluated in vitro. Moreover, the dynamic alteration of bioactive flavonoids in CRP collected at different time and its correlation with anti-lipase activities was investigated.

STUDY DESIGN/METHODS

Quantitative analysis of multi-components by a single-marker (QAMS) method was developed and validated for simultaneous determination of six flavonoids including narirutin, hesperidin, didymin, nobiletin, 3,5,6,7,8,3',4'-heptamethoxyflavone and tangeretin. Anti-lipase activity evaluation and docking studies of the flavonoids was also carried out to screen out the candidate lipase inhibitors.

RESULTS

The QAMS method validation results exhibited that the developed method had desirable specificity, linearity, precision and accuracy. CRP collected in early months contained higher concentrations of bioactive flavonoids, and exhibited more potent anti-lipase activity.

CONCLUSION

Harvest timing had a significant impact on the amounts of bioactive flavonoids and the anti-lipase activities of CRP extracts. The contents of total flavonoids were positively correlated with the anti-lipase activities of CRP, and polymethoxyflavones played a significant role in the hypolipidemic effect of CRP. Nobiletin might be the most potential lipase inhibitor in CRP.

Green Tea Polyphenols Modulate Colonic Microbiota Diversity and Lipid Metabolism in High-Fat Diet Treated HFA Mice

There is an increasing interest in the effect of dietary polyphenols on the intestinal microbiota and the possible associations between this effect and the development of obesity. However, limited information is available on how these polyphenols affect the gut microbiota and lipid metabolism. The co-action of a high-fat diet (HFD) and tea polyphenol (TP) on gut microbiota and lipid metabolism using a human flora-associated (HFA) C57BL/6J mice model is studied. TP reduced serum total cholesterol, triglyceride, low density lipoprotein, glucose (GLU) and insulin (INS) levels of HFD mice in a dose-dependent manner (P < 0.01). TP also significantly increased acetic acid and butyric acid levels in HFA mice. 16S rRNA V3 region Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis (PCR-DGGE) profiles showed that HFD mice had significantly reduced microbial diversity. This reduction could be alleviated by TP, with a significant increase in the richness and diversity of colonic microbiota in the high-fat diet with 0.2% TP (TPM) and high-fat diet with 0.05% TP (TPL) groups (P < 0.05). 454 pyrosequencing analysis showed that the HFD group had a significant increase in the Bacteroidetes to Firmicutes (F/B) ratio (P < 0.001), which could effectively be reversed by TP. The results showed that the changes in composition and diversity of colonic microbiota by TP administration suppressed the host body weight and blood lipid increase in high-fat diet HFA mice.

PRACTICAL APPLICATION

A high fat diet significantly impacted gut microbiota composition and lipid metabolism in human flora-associated mice, which were largely ameliorated by tea polyphenol (TP). Therefore, TPs may be effectively used in controlling or treating obesity, hyperlipidemia and other related metabolic diseases.

The Inhibitory Effects of Anthocyanin-Rich Sunrouge Tea on Pancreatic Lipase Activity

This study investigated the in vitro and in vivo effects of Sunrouge (SR), which is an anthocyaninrich green tea. Hot and cold water extracts (CWEX) of Yabukita (YK; regular green tea), SR second crop (SR2), and SR third crop (SR3) were prepared. The 50% inhibitory concentrations for YK, SR2, and SR3 CWEXs against pancreatic lipase in vitro were 12.3±2.8, 6.2±0.3, and 4.0±1.1 mg/mL, respectively. Epigallocatechin gallate (EGCG) accounted for 4.3%, 6.0%, and 6.3% of YK, SR2, and SR3 CWEXs, respectively. SR2 had the highest anthocyanin content of these three samples. In vivo, the increase in the plasma triacylglycerol (TG) concentration following oral administration of oil to mice was significantly suppressed at 60 and 120 min in animals treated with SR2. No significant differences were observed between the plasma TG concentration in the YK and control groups. These results suggested that concomitant administration of SR with oil may suppress lipid absorption and that EGCG may exert this effect.

Antioxidants from black and green tea: from dietary modulation of oxidative stress to pharmacological mechanisms

The consumption of tea (Camellia sinensis) has been correlated with a low incidence of chronic pathologies, such as cardiovascular disease and cancer, in which oxidative stress plays a critical role. Tea catechins and theaflavins are, respectively, the bioactive phytochemicals responsible for the antioxidant activity of green tea (GT) and black tea (BT). In addition to their redox properties, tea catechins and theaflavins could have also pharmacological activities, such as the ability to lower glucose, lipid and uric acid (UA) levels. These activities are mediated by pharmacological mechanisms such as enzymatic inhibition and interaction with transporters. Epigallocatechin gallate is the most active compound at inhibiting the enzymes involved in cholesterol and UA metabolism (hydroxy-3-methyl-glutaryl-CoA reductase and xanthine oxidase respectively) and affecting glucose transporters. The structural features of catechins that significantly contribute to their pharmacological effect are the presence/absence of the galloyl moiety and the number and positions of the hydroxyl groups on the rings. Although the inhibitory effects on α-glucosidase, maltase, amylase and lipase, multidrug resistance 1, organic anion transporters and proton-coupled folate transport occur at higher concentrations than those apparent in the circulation, these effects could be relevant in the gut. In conclusion, despite the urgent need for further research in humans, the regular consumption of moderate quantities of GT and BT can effectively modulate their antioxidant capacity, mainly in people subjected to oxidative stress, and could improve the metabolism of glucose, lipid and UA.

LINKED ARTICLES

This article is part of a themed section on Principles of Pharmacological Research of Nutraceuticals. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v174.11/issuetoc.

Nine Different Chemical Species and Action Mechanisms of Pancreatic Lipase Ligands Screened Out from Forsythia suspensa Leaves All at One Time

It is difficult to screen out as many active components as possible from natural plants all at one time. In this study, subfractions of Forsythia suspensa leaves were firstly prepared; then, their inhibitive abilities on pancreatic lipase were tested; finally, the highest inhibiting subfraction was screened by self-made immobilized pancreatic lipase. Results showed that nine ligands, including eight inhibitors and one promotor, were screened out all at one time. They were three flavonoids (rutin, IC₅₀: 149 ± 6.0 μmol/L; hesperidin, 52.4 μmol/L; kaempferol-3-O-rutinoside, isolated from F. suspensa leaves for the first time, IC₅₀ notably reached 2.9 ± 0.5 μmol/L), two polyphenols (chlorogenic acid, 3150 ± 120 μmol/L; caffeic acid, 1394 ± 52 μmol/L), two lignans (phillyrin, promoter; arctigenin, 2129 ± 10.5 μmol/L), and two phenethyl alcohol (forsythiaside A, 2155 ± 8.5 μmol/L; its isomer). Their action mechanisms included competitive inhibition, competitive promotion, noncompetitive inhibition, and uncompetitive inhibition. In sum, using the appropriate methods, more active ingredients can be simply and quickly screened out all at one time from a complex natural product system. In addition, F. suspensa leaves contain numerous inhibitors of pancreatic lipase.