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

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.

Inhibition of pancreatic lipase by black tea theaflavins: Comparative enzymology and in silico modeling studies

Few studies have examined the effect of black tea (Camellia sinensis) theaflavins on obesity-related targets. Pancreatic lipase (PL) plays a central role in fat metabolism and is a validated target for weight loss. We compared the inhibitory efficacy of individual theaflavins and explored the underlying mechanism. Theaflavin-3,3'-digallate (TFdiG), theaflavin-3'-gallate, theaflavin-3-gallate, and theaflavin inhibited PL with IC50 of 1.9, 4.2, 3.0, and >10μmol/L. The presence and location of the galloyl ester moiety were essential for inhibitory potency. TFdiG exhibited mixed inhibition with respect to substrate concentration. In silico modeling showed that theaflavins bind to Asn263 and Asp206, which form a pocket adjacent to the active site, and galloyl-containing theaflavins are then predicted to perturb the protonation of His264. These data provide a putative mechanism to explain the anti-obesity effects of tea.

Opposite Structural Effects of Epigallocatechin-3-gallate and Dopamine Binding to α-Synuclein

The intrinsically disordered and amyloidogenic protein α-synuclein (AS) has been linked to several neurodegenerative states, including Parkinson's disease. Here, nanoelectrospray-ionization mass spectrometry (nano-ESI-MS), ion mobility (IM), and native top-down electron transfer dissociation (ETD) techniques are employed to study AS interaction with small molecules known to modulate its aggregation, such as epigallocatechin-3-gallate (EGCG) and dopamine (DA). The complexes formed by the two ligands under identical conditions reveal peculiar differences. While EGCG engages AS in compact conformations, DA preferentially binds to the protein in partially extended conformations. The two ligands also have different effects on AS structure as assessed by IM, with EGCG leading to protein compaction and DA to its extension. Native top-down ETD on the protein-ligand complexes shows how the different observed modes of binding of the two ligands could be related to their known opposite effects on AS aggregation. The results also show that the protein can bind either ligand in the absence of any covalent modifications, such as oxidation.

Natural Inhibitors of Lipase: Examining Lipolysis in a Single Droplet

Inhibition of lipase activity is one of the approaches to reduced fat intake with nutritional prevention promoting healthier diet. The food industry is very interested in the use of natural extracts, hence reducing the side effects of commercial drugs inhibiting lipolysis. In this work we propose a novel methodology to rapidly assess lipolysis/inhibition in a single droplet by interfacial tension and dilatational elasticity. The evolution of the interfacial tension of lipase in simplified duodenal fluid in the absence and that in the presence of the pharmaceutical drug Xenical are the negative (5 ± 1 mN/m) and positive (9 ± 1 mN/m) controls of the inhibition of lipolysis, respectively. Then, we correlate the inhibition with the reduction of the interfacial activity of lipase and further identify the mode of action of the inhibition based on dilatational response (conformational changes induced in the molecule/blocking of adsorption sites). This work provides new insight into the lipase inhibition mechanism and a rapid methodology to identify the potential of new natural inhibitors.

Therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial

BACKGROUND AND AIMS

To examine the effect and safety of high-dose green tea extract (Epigallocatechin gallate, EGCG) at a daily dosage of 856.8 mg on weight reduction and changes of lipid profile and obesity-related hormone peptides in women with central obesity.

METHODS

We conducted a randomized, double-blind trial registered under ClinicalTrials.gov Identifier no. NCT02147041. A total of 115 women with central obesity were screened at our clinic. 102 of them with a body mass index (BMI) ≥ 27 kg/m(2) and a waist circumference (WC) ≥ 80 cm were eligible for the study. These women were randomly assigned to either a high-dose green tea group or placebo group. The total treatment time was 12 weeks. The main outcome measures were anthropometric measurements, lipid profiles, and obesity related hormone peptides including leptin, adiponectin, ghrelin, and insulin.

RESULTS

Significant weight loss, from 76.8 ± 11.3 kg to 75.7 ± 11.5 kg (p = 0.025), as well as decreases in BMI (p = 0.018) and waist circumference (p = 0.023) were observed in the treatment group after 12 weeks of high-dose EGCG treatment. This study also demonstrated a consistent trend of decreased total cholesterol, reaching 5.33%, and decreased LDL plasma levels. There was good tolerance of the treatment among subjects without any side effects or adverse events. Significantly lower ghrelin levels and elevated adiponectin levels were detected in the study group than in the placebo group.

CONCLUSION

12 weeks of treatment with high-dose green tea extract resulted in significant weight loss, reduced waist circumference, and a consistent decrease in total cholesterol and LDL plasma levels without any side effects or adverse effects in women with central obesity. The antiobestic mechanism of high-dose green tea extract might be associated in part with ghrelin secretion inhibition, leading to increased adiponectin levels.

Mode of pancreatic lipase inhibition activity in vitro by some flavonoids and non-flavonoid polyphenols

Numerous reports have shown plant metabolites as potential inhibitors of pancreatic lipase (PL). The most notable group is plant polyphenols. However, a limited number of reports diagnosed their mode of inhibition delineating conflicting results. To elucidate the kinetic mode of PL inhibition, some selected flavonoid and non-flavonoid polyphenol standards were first screened for their lipase inhibition potency by their half maximal inhibitory concentration (IC₅₀) followed by inhibition kinetic analysis. Of the phenolics tested, only gallic acid (GA) and galloyl moiety containing epicatechin, viz., epigallocatechin (EGC) and epigallocatechin gallate (EGCG) showed, comparative to others, higher PL inhibitions (IC₅₀, 387.2, 237.3, and 391.2μM respectively). Analysis of enzyme inhibition modalities at various substrate concentrations revealed a dose-dependent inhibition of reaction velocity. Inhibitory rates decreased by the order of EGCG>EGC>GA (Ki, 13.29>35.0>44.61μM respectively). The results, when verified by visual inspection of Lineweaver-Burk as well as Dixon plots, showed inhibitions of PL by GA, EGC, and EGCG that were best fit to competitive inhibitions. A role of the galloyl moiety in enzyme-inhibitor binding has been evident from their structural resemblance. Depicting it further, ethyl gallate (EG), showed a similar competitive inhibition, therefore, indicating a galloyl moiety driven competitive inhibition of PL.

Inhibitory activities of caffeoylquinic acid derivatives from Ilex kudingcha C.J. Tseng on α-glucosidase from Saccharomyces cerevisiae

Polyphenols and caffeoylquinic acid (CQA) derivatives (3-CQA, 4-CQA, 5-CQA, 3,4-diCQA, 3,5-diCQA, and 4,5-diCQA) were prepared from Ilex kudingcha C.J. Tseng, and their effects and mechanisms on the activities of α-glucosidase from Saccharomyces cerevisiae were investigated in the present study. As results, the IC50 values for CQA derivatives were 0.16-0.39 mg/mL, and the inhibition mode of CQA derivatives was noncompetitive. On the basis of fluorescence spectroscopy and circular dichroism spectroscopy data, the binding constants and number of binding sites were calculated to be 10(6)-10(8) M(-1) and 1.42-1.87, respectively. CQA derivatives could bind to the enzyme mainly through hydrophobic interaction, altering the microenvironment and molecular conformation of the enzyme, thus decreasing the catalytic activity. To the authors' knowledge, this is the first report on α-glucosidase inhibitory mechanism by CQA derivatives from I. kudingcha, and the findings suggest a potential use of kudingcha as functional foods for the prevention and treatment of diabetes and related symptoms.

Complexes of green tea polyphenol, epigalocatechin-3-gallate, and 2S albumins of peanut

2S albumins of peanuts are seed storage proteins, highly homologous in structure and described as major elicitors of anaphylactic reactions to peanut (allergens Ara h 2 and Ara h 6). Epigallocatechin-3-gallate (EGCG) is the most biologically potent polyphenol of green tea. Non-covalent interactions of EGCG with proteins contribute to its diverse biological activities. Here we used the methods of circular dichroism, fluorescence quenching titration, isothermal titration calorimetry and computational chemistry to elucidate interactions of EGCG and 2S albumins. Similarity in structure and overall fold of 2S albumins yielded similar putative binding sites and similar binding modes with EGCG. Binding affinity determined for Ara h 2 was in the range described for complexes of EGCG and other dietary proteins. Binding of EGCG to 2S albumins affects protein conformation, by causing an α-helix to β-structures transition in both proteins. 2S albumins of peanuts may be good carriers of physiologically active green tea catechin.

Efficacy of green tea extract in two exercise models

Oral administration of green tea extract in a dose of 6 mg/kg twice a day (before and after exercise) over 2 weeks significantly increased swimming times on week 1 and 2 in comparison with control animals receiving water. The 7-day and final exhaustive running in rats was accompanied by a significant decrease in spleen weight and iron serum levels associated with developed reticulocytosis. Administration of green tea extract in a dose of 12 mg/kg once a day (before exercise) for 2 weeks did not affect the duration of the running, but prevented the decrease in serum iron and spleen weight, that, along with a significantly increased concentration of reduced glutathione in erythrocytes, can indicate a normalizing effect of green tea extract on hemopoiesis and stimulating effect on the antioxidant system of erythrocytes.

Structure Activity Related, Mechanistic, and Modeling Studies of Gallotannins containing a Glucitol-Core and α-Glucosidase

Gallotannins containing a glucitol core, which are only produced by members of the maple (Acer) genus, are more potent α-glucosidase inhibitors than the clinical drug, acarbose. While this activity is influenced by the number of substituents on the glucitol core (e.g. more galloyl groups leads to increased activity), the mechanisms of inhibitory action are not known. Herein, we investigated ligand-enzyme interactions and binding mechanisms of a series of 'glucitol-core containing gallotannins (GCGs)' against the α-glucosidase enzyme. The GCGs included ginnalins A, B and C (containing two, one, and one galloyl/s, respectively), maplexin F (containing 3 galloyls) and maplexin J (containing 4 galloyls). All of the GCGs were noncompetitive inhibitors of α-glucosidase and their interactions with the enzyme were further explored using biophysical and spectroscopic measurements. Thermodynamic parameters (by isothermal titration calorimetry) revealed a 1:1 binding ratio between GCGs and α-glucosidase. The binding regions between the GCGs and α-glucosidase, probed by a fluorescent tag, 1,1'-bis(4-anilino-5-napththalenesulfonic acid, revealed that the GCGs decreased the hydrophobic surface of the enzyme. In addition, circular dichroism analyses showed that the GCGs bind to α-glucosidase and lead to loss of the secondary α-helix structure of the protein. Also, molecular modeling was used to predict the binding site between the GCGs and the α-glucosidase enzyme. This is the first study to evaluate the mechanisms of inhibitory activities of gallotannins containing a glucitol core on α-glucosidase.