Green tea extract decreases starch digestion and absorption from a test meal in humans: a randomized, placebo-controlled crossover study

Rice with a healthier glycaemic profile: Unveiling the molecular mechanisms and breeding strategies for the future

Rice is a staple food crop consumed by billions globally. However, rice consumption is associated with a high glycaemic response, which has negative health implications. Identifying rice varieties with intrinsically lower glycaemic responses would benefit public health. Recent research has uncovered genomic loci in rice associated with glycaemic response in rice. However, diagnostic assays are needed to efficiently characterize these loci in rice germplasm and breeding populations. This review summarizes current knowledge on low glycaemic rice genetics and proposes strategies for diagnostic assay development. Specific loci implicated in modulating starch digestion and glycaemic response are highlighted. Developing robust, high-throughput molecular marker platform for low glycaemic rice loci will accelerate varietal improvement and enhance the nutritional qualities and health benefits of this essential crop. The review also explores the role of other grain components, such as lipids and proteins, and their interactions with starch in influencing the glycaemic index (GI).

Effect of Ultrasound-Assisted Extraction and Drying Methods on Bioactive Compounds, Phenolic Composition, and Antioxidant Activity of Assam Tea Cultivar (Camellia sinensis var. assamica) Cultivated in Thailand

Tea is a rich source of phytochemicals; their composition in tea extracts varies depending on the cultivar, climate, production region, and processing and handling processes. The method of extraction plays a crucial role in determining the biological effects of the bioactive compounds in tea leaves. However, reports on the catechin profiles and antioxidant activities of the extracts obtained from leaves at different stages of maturity are limited. Here, we aimed to evaluate the effect of ultrasound-assisted extraction (UAE) and different drying methods, freeze drying (FD) and spray drying (SD), on the composition of bioactive compounds, phenolic composition, and antioxidant activity of extracts obtained from different part of leaves, top (TT), middle (ML), and mature (MT), of Assam tea cultivar (Camellia sinensis var. assamica) cultivated in Thailand (Thai Assam tea). High-performance liquid chromatography analysis showed that the extracts obtained by UAE with FD from TT leaves (UAEFD-TT) had the highest catechins (341.38 ± 0.11 mg/g extract) and caffeine (93.20 ± 0.36 mg CF/g extract) contents compared with those extracted from ML and MT using the same method as well those obtained by SD. The total phenolic and total flavonoid contents were the highest in UAEFD-TT extracts (456.78 ± 4.31 mg GAE/g extract and 333.98 ± 0.83 mg QE/g extract, respectively). In addition, UAEFD-TT exhibited the highest antioxidant activity; the IC50 values obtained by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays were 1.31 ± 0.02 and 7.51 ± 0.03 μg/mL, respectively. In the ferric-reducing antioxidant power (FRAP) assay, the UAEFD-TT extract demonstrated the highest antioxidant activity (324.54 ± 3.33 μM FeSO4/mg extract). These results suggest that extraction from TT using UAE followed by FD produced the highest amount of antioxidant compounds in Thai Assam tea extracts.

Psychological determinants of the effectiveness of conjugated linoleic acid supplementation in overweight and obese women-a randomized controlled trial

Introduction

Previous studies investigating the effectiveness of conjugated linoleic acid (CLA) supplementation in body weight reduction provided unequivocal results. We hypothesized that psychological factors such as self-efficacy, locus of control or dispositional optimism can affect the success of the intervention. Therefore, this study aimed to determine the psychological factors that modulate the effectiveness of CLA supplementation in overweight or obese women and affect the ability to successfully complete the study.

Methods

In total, 74 subjects were recruited into this three-month randomized trial and divided into intervention and control groups receiving, respectively, capsules containing 3 g 80% CLA per day and capsules containing 3 g of sunflower oil. The following psychological tests were performed before the intervention: Multidimensional Health Locus of Control scale, Acceptance of Illness Scale, Satisfaction with Life Scale (SWLS), General Self Efficacy Scale (GSES), Health Behavior Inventory scale and Life Orientation Test (LOT-R).

Results

A total of 60 women completed the study and the subjects who dropped out obtained higher scores in the GSES (p = 0.0490) and the LOT-R (p = 0.0087) tests than subjects who completed the trial. Besides, multivariate linear regression demonstrated that the SWLS test (p = 0.0345) results were independent predictors of body weight changes.

Conclusion

In conclusion, psychological factors like self-efficacy and optimism may be associated with a higher risk of withdrawal from the study, while satisfaction with life may have an impact on the effectiveness of body weight reduction.Clinical trial registration: [https://drks.de/search/en], identifier [DRKS00010462].

The impact of mulberry leaf extract at three different levels on reducing the glycemic index of white bread

In this study, the influences of mulberry leaf extract (MLE) addition on the physicochemical properties including the specific volume, texture and sensory features of white bread (WB) were evaluated by the sensory analysis technology. A double-blind, randomised, repeat-measure design was used to study the impact of MLE addition on the postprandial blood glucose response as well as the satiety index of WB. Results showed that the addition of MLE showed no significant effects on the physicochemical properties of WB except for the slight changes of color and bitterness. The addition of MLE significantly reduced the total blood glucose rise after ingestion of WB over 120 minutes, and reduced the GI value of WB in a dose-effect relationship. When the concentration of MLE reached 1.5 g per 100 g available carbohydrate, the GI value of WB could be reduced from 77 to 43. This study provides important information in terms of the appropriateness of MLE when added to more complex real food, the dose-dependent relationship could supply a reference for the application of MLE.

Purple tea: chemical characterization and evaluation as inhibitor of pancreatic lipase and fat digestion in mice

A variety of the classic green tea plant, Camellia sinensis, was developed and is exclusive to Kenya. Due to high content of anthocyanin polyphenols in its leaves, the beverage obtained from this variety is purple in color and is the origin of the name purple tea. This work had two main purposes. The first one was to identify and quantify the major anthocyanin polyphenols in a hot water aqueous extract of the purple tea leaves. The second one was to test the hypothesis if this extract is capable of inhibiting triglyceride absorption considering that anthocyanin polyphenolics have been frequently associated to antilipidemic effects. Parallel experiments were always done with a similar green tea extract for comparison purposes. The antioxidant, anti-inflammatory, and cytotoxic activities of both tea varieties are similar. The purple tea extract, however, was strongly inhibitory toward the pancreatic lipase (minimal IC₅₀ = 67.4 μg mL^-1), whereas the green tea preparation was a weak inhibitor. Triglyceride digestion in mice was inhibited by the purple tea extract starting at 100 mg kg^-1 dose and with a well-defined dose dependence. Green tea had no effect on triglyceride digestion at doses up to 500 mg kg^-1. The latter effect is probably caused by several components in the purple tea extract including non-anthocyanin and anthocyanin polyphenols, the first ones acting solely via the inhibition of the pancreatic lipase and the latter by inhibiting both the lipase and the transport of free fatty acids from the intestinal lumen into the circulating blood. The results suggest that the regular consumption of Kenyan purple tea can be useful in the control of obesity.

Therapeutic potential of non-starch polysaccharides on type 2 diabetes: from hypoglycemic mechanism to clinical trials

Non-starch polysaccharides (NSPs) have been reported to exert therapeutic potential on managing type 2 diabetes mellitus (T2DM). Various mechanisms have been proposed; however, several studies have not considered the correlations between the anti-T2DM activity of NSPs and their molecular structure. Moreover, the current understanding of the role of NSPs in T2DM treatment is mainly based on in vitro and in vivo data, and more human clinical trials are required to verify the actual efficacy in treating T2DM. The related anti-T2DM mechanisms of NSPs, including regulating insulin action, promoting glucose metabolism and regulating postprandial blood glucose level, anti-inflammatory and regulating gut microbiota (GM), are reviewed. The structure-function relationships are summarized, and the relationships between NSPs structure and anti-T2DM activity from clinical trials are highlighted. The development of anti-T2DM medication or dietary supplements of NSPs could be promoted with an in-depth understanding of the multiple regulatory effects in the treatment/intervention of T2DM.

Metabolomics-based profiling of 4 avocado varieties using HPLC-MS/MS and GC/MS and evaluation of their antidiabetic activity

Seven avocado "Persea americana" seeds belonging to 4 varieties, collected from different localities across the world, were profiled using HPLC-MS/MS and GC/MS to explore the metabolic makeup variabilities and antidiabetic potential. For the first time, 51 metabolites were tentatively-identified via HPLC-MS/MS, belonging to different classes including flavonoids, biflavonoids, naphthodianthrones, dihydrochalcones, phloroglucinols and phenolic acids while 68 un-saponified and 26 saponified compounds were identified by GC/MS analysis. The primary metabolic variabilities existing among the different varieties were revealed via GC/MS-based metabolomics assisted by unsupervised pattern recognition methods. Fatty acid accumulations were proved as competent, and varietal-discriminatory metabolites. The antidiabetic potential of the different samples was explored using in-vitro amylase and glucosidase inhibition assays, which pointed out to Gwen (KG) as the most potent antidiabetic sample. This could be attributed to its enriched content of poly-unsaturated fatty acids and polyphenolics. Molecular docking was then performed to predict the most promising phytoligands in KG variety to be posed as antidiabetic drug leads. The highest in-silico α-amylase inhibition was observed with chrysoeriol-4'-O-pentoside-7-O-rutinoside, apigenin-7-glucuronide and neoeriocitrin which might serve as potential drug leads for the discovery of new antidiabetic remedies.

The inhibitory action of purple tea on in vivo starch digestion compared to other Camellia sinensis teas

In order to contribute to improve knowledge about the actions of Camellia sinensis extracts on starch digestion, several varieties were compared. The latter were green, oolong, white, black, and purple teas. The results are hoped to contribute to our understanding of the mode of action and potency of the various tea preparations as possible adjuvants in the control of post-prandial glycemia. The extracts were prepared in way similar to their form of consumption. All extracts decreased starch digestion, but the purple tea extract was the strongest inhibitor, their inhibitory tendency started at the dose of 50 mg/kg and was already maximal with 250 mg/kg. Maltose tolerance was not significantly affected by the extracts. Glucose tolerance was not affected by purple tea, but black tea clearly diminished it; green tea presented the same tendency. Purple tea was also the strongest inhibitor of pancreatic α-amylase, followed by black tea. The green tea, oolong tea, and white tea extracts tended to stimulate the pancreatic α-amylase at low concentrations, a phenomenon that could be counterbalancing its inhibitory effect on starch digestion. Based on chemical analyses and molecular docking simulations it was concluded that for both purple and black tea extracts the most abundant active component, epigallocatechin gallate, seems also to be the main responsible for the inhibition of the pancreatic α-amylase and starch digestion. In the case of purple tea, the inhibitory activity is likely to be complemented by its content in deoxyhexoside-hexoside-containing polyphenolics, especially the kaempferol and myricetin derivatives. Polysaccharides are also contributing to some extent. Cyanidins, the compounds giving to purple tea its characteristic color, seem not to be the main responsible for its effects on starch digestion. It can be concluded that in terms of postprandial anti-hyperglycemic action purple tea presents the best perspectives among all the tea varieties tested in the present study.

Borate and phosphite treatments of potato plants (Solanum tuberosum L.) as a proof of concept to reinforce the cell wall structure and reduce starch digestibility

Potatoes are one of the main sources of carbohydrates in human diet, however they have a high glycaemic index (GI). Hence, developing new agricultural and industrial strategies to produce low GI potatoes represents a health priority to prevent obesity and related diseases. In this work, we investigated whether treatments of potato plants with elicitors of plant defence responses can lead to a reduction of tuber starch availability and digestibility, through the induction of cell wall remodelling and stiffening. Treatments with phosphites (KPhi) and borate were performed, as they are known to activate plant defence responses that cause modifications in the architecture and composition of the plant cell wall. Data of suberin autofluorescence demonstrated that potato plants grown in a nutrition medium supplemented with KPhi and borate produced tubers with a thicker periderm, while pectin staining demonstrated that KPhi treatment induced a reinforcement of the wall of storage parenchyma cells. Both compounds elicited the production of H₂O₂, which is usually involved in cell-wall remodelling and stiffening reactions while only KPhi caused an increase of the total content of phenolic compounds. A two-phase digestion in vitro assay showed that treatment with KPhi determined a significant decrease of the starch hydrolysis rate in potato tubers. This work highlights the ability of cell wall architecture in modulating starch accessibility to digestive enzymes, paving the way for new agronomic practices to produce low GI index potatoes.

Polyphenolic inhibition of enterocytic starch digestion enzymes and glucose transporters for managing type 2 diabetes may be reduced in food systems

With the current global surge in diabetes cases, there is a growing interest in slowing and managing diabetes and its effects. While there are medications that can be used, they have adverse side effects such as hypoglycemia and weight gain. To overcome these problems, bioactive compounds commonly found in fruits, vegetables and cereal grains are used to slow starch digestion and transport of simple sugars across the intestinal epithelia thereby reducing plasma blood glucose spike. These effects are achieved through inhibition of amylases, glucosidases and glucose transporters present in the gastrointestinal tract and brush boarder membrane. The extent of inhibition by polyphenols is dependent on molecular structure, doses and food matrix. Glycemic lowering effect of polyphenols have been demonstrated both in in vivo and in vitro studies. However, when these compounds are incorporated in food systems, they can interact with other polymers in the food matrix leading to lesser inhibition of digestion and/or glucose transporters compared to isolated or pure compounds as often witnessed in most in vitro studies.

Hypoglycemic effect of soluble polysaccharide and catechins from green tea on inhibiting intestinal transport of glucose

BACKGROUND

Water soluble polysaccharide derived from green tea (WSP) is produced as byproducts when catechins were extracted from green tea. Although inhibitory effect of green tea catechins on the glucose transport in small intestine has been studied, the hypoglycemic efficacy of the WSP or its combinational effect has not been studied. In order to investigate hypoglycemic efficacy of the WSP or its combinational effect with green tea extract (GTE), co-consumption of GTE and WSP with wheat starch was investigated using in vitro digestion coupled with Caco-2 cells. The mechanism of the intestinal glucose transport was elucidated throughout the gene expression of the intestinal glucose transporters, which included sodium dependent glucose transporter (SGLT1) and glucose transporter 2 (GLUT2), using quantitative real-time polymerase chain reaction (qRT-PCR).

RESULTS

The co-digestion of wheat starch with GTE during the small intestinal phase was the most rapidly digested into reducing sugar (73.96 g L^-1 ) compared to itself (48.44 g L^-1 ), WSP (60.35 g L^-1 ), and GTE + WSP (61.81 g L^-1 ). Intestinal glucose transport was 11.82, 7.59, 4.49, and 2.40% for wheat starch, wheat starch with GTE, WSP, and GTE + WSP, respectively. The highest decreased expression pattern in SGLT1 was observed when cells treated with wheat starch + GTE + WSP (0.66-fold) compared to GTE or WSP treatment.

CONCLUSION

The results suggested that co-consumption of green tea derived products with wheat starch could delay the intestinal absorption of glucose. Results from the current study suggested that GTE and WSP could be the useful supplements of dietary therapy for hyperglycemia to delay glucose absorption. © 2020 Society of Chemical Industry.

Influence of Herbal Medicines on HMGB1 Release, SARS-CoV-2 Viral Attachment, Acute Respiratory Failure, and Sepsis. A Literature Review

By attaching to the angiotensin converting enzyme 2 (ACE2) protein on lung and intestinal cells, Sudden Acute Respiratory Syndrome (SARS-CoV-2) can cause respiratory and homeostatic difficulties leading to sepsis. The progression from acute respiratory failure to sepsis has been correlated with the release of high-mobility group box 1 protein (HMGB1). Lack of effective conventional treatment of this septic state has spiked an interest in alternative medicine. This review of herbal extracts has identified multiple candidates which can target the release of HMGB1 and potentially reduce mortality by preventing progression from respiratory distress to sepsis. Some of the identified mixtures have also been shown to interfere with viral attachment. Due to the wide variability in chemical superstructure of the components of assorted herbal extracts, common motifs have been identified. Looking at the most active compounds in each extract it becomes evident that as a group, phenolic compounds have a broad enzyme inhibiting function. They have been shown to act against the priming of SARS-CoV-2 attachment proteins by host and viral enzymes, and the release of HMGB1 by host immune cells. An argument for the value in a nonspecific inhibitory action has been drawn. Hopefully these findings can drive future drug development and clinical procedures.

Inhibition of the facilitative sugar transporters (GLUTs) by tea extracts and catechins

Tea polyphenolics have been suggested to possess blood glucose lowering properties by inhibiting sugar transporters in the small intestine and improving insulin sensitivity. In this report, we studied the effects of teas and tea catechins on the small intestinal sugar transporters, SGLT1 and GLUTs (GLUT1, 2 and 5). Green tea extract (GT), oolong tea extract (OT), and black tea extract (BT) inhibited glucose uptake into the intestinal Caco-2 cells with GT being the most potent inhibitor (IC₅₀ : 0.077 mg/mL), followed by OT (IC₅₀ : 0.136 mg/mL) and BT (IC₅₀ : 0.56 mg/mL). GT and OT inhibition of glucose uptake was partial non-competitive, with an inhibitor constant (K_i ) = 0.0317 and 0.0571 mg/mL, respectively, whereas BT was pure non-competitive, K_i  = 0.36 mg/mL. Oocytes injected to express small intestinal GLUTs were inhibited by teas, but SGLT1 was not. Furthermore, catechins present in teas were the predominant inhibitor of glucose uptake into Caco-2 cells, and gallated catechins the most potent: CG > ECG > EGCG ≥ GCG when compared to the non-gallated catechins (C, EC, GC, and EGC). In Caco-2 cells, individual tea catechins reduced the SGLT1 gene, but not protein expression levels. In contrast, GLUT2 gene and protein expression levels were reduced after 2 hours exposure to catechins but increased after 24 hours. These in vitro studies suggest teas containing catechins may be useful dietary supplements capable of blunting postprandial glycaemia in humans, including those with or at risk to Type 2 diabetes mellitus.

Enrichment of Biscuits with Matcha Green Tea Powder: Its Impact on Consumer Acceptability and Acute Metabolic Response

Matcha green tea powder (MGTP) is made with finely ground green tea leaves that are rich in phytochemicals, most particularly catechins. Shortbread biscuits were enriched with MGTP and evaluated for consumer acceptability and potential functional health properties. Baking decreased the content of total catechins by 19% compared to dough, although epimerization increased the amount of (+)-gallocatechin gallate at the expense of other catechins such as (−)-epigallocatechin gallate. Consumer acceptability tests using a 9-point hedonic scale showed that consumers preferred enriched biscuits with low content of MGTP (2 g of MGTP 100 g⁻¹ of flour), and an increase of sugar content did not significantly improve the acceptability of MGTP-enriched biscuits. Overall, enrichment of biscuits with MGTP did not significantly affect the postprandial glucose or triglyceride response (area under curve) compared to non-enriched biscuits consumed with water or MGTP drink. Enriching biscuits with Matcha green tea is acceptable to consumers, but may not bring significant postprandial effects.

The nutritional property of endosperm starch and its contribution to the health benefits of whole grain foods

Purported health benefits of whole grain foods in lowering risk of obesity, type 2 diabetes, cardiovascular disease, and cancer are supported by epidemiological studies and scientific researches. Bioactive components including dietary fibers, phytochemicals, and various micronutrients present in the bran and germ are commonly considered as the basis for such benefits. Endosperm starch, as the major constituent of whole grains providing glucose to the body, has been less investigated regarding its nutritional property and contribution to the value of whole grain foods. Nutritional quality of starch is associated with its rate of digestion and glucose absorption. In whole grain foods, starch digestion and glucose delivery may vary depending on the form in which the food is delivered, some with starch being rapidly and others slowly digested. Furthermore, there are other inherent factors in whole grain products, such as phenolic compounds and dietary fibers, that may moderate glycemic profiles. A good understanding of the nutritional properties of whole grain starch is important to the development of food processing technologies to maximize their health benefits.

Interactions of flavonoids with α-amylase and starch slowing down its digestion

Hydrophobic flavonoids can suppress starch digestion in the intestine by forming starch-flavonoid complexes.

Conjugated linoleic acid does not affect digestion and absorption of fat and starch-a randomized, double-blinded, placebo-controlled parallel study

OBJECTIVE

Conjugated linoleic acid (CLA) is known as a potent agent for altering body weight and composition. However, its effect on the process of digestion is still unknown. The aim of this study has been to elucidate the effect of a 3-month supplementation with CLA on starch and fat digestion and absorption in humans.

APPROACH

The study included 74 obese and overweight adults who were randomized to receive 3.0 g of CLA or sunflower oil as placebo daily for 3 months. Digestion and absorption of fat and starch was assessed using non-invasive breath tests with a stable ¹³C isotope (cumulative percentage dose recovery, CPDR) before and after the supplementation period. To exclude the effect of oxidation, in addition total energy expenditure (TTE) was measured by a ¹³C bicarbonate breath test.

RESULTS

The changes in CPDR values (∆CPDR median 〈interquartile range〉) were no different between subjects from the CLA group and the placebo group (fat: -0.2 〈-9.1-4.1〉 versus 0.6 〈-7.0-8.0〉, p < 0.4796; starch: -1.3 〈-9.5-2.4〉 versus -1.0 〈-5.1-1.7〉, p < 0.5520, respectively). The incidence of negative and positive values of ∆CPDR was no different between groups [for fat: 53.1% versus 46.7%, RR 1.138, (95% CI 0.689-1.882) and for starch: 67.7% versus 56.7%, RR 1.195, (95% CI 0.804-1.777)]. The changes in TTE did not differ between the CLA and the placebo group (respectively 1 〈48; 267〉 versus -8 〈-120;93〉 kcal; p < 0.2728).

CONCLUSION

Supplementation with CLA for 3 months did not affect fat and starch digestion assessed by ¹³C mixed triglyceride breath test and ¹³C starch breath test.

The Role of Dietary Phenolic Compounds in Protein Digestion and Processing Technologies to Improve Their Antinutritive Properties

Digestion is the key step for delivering nutrients and bioactive substances to the body. The way different food components interact with each other and with digestive enzymes can modify the digestion process and affect human health. Understanding how food components interact during digestion is essential for the rational design of functional food products. Plant polyphenols have gained much attention for the bioactive roles they play in the human body. However, their strong beneficial effects on human health have also been associated with a negative impact on the digestion process. Due to the generally low absorption of phenolic compounds after food intake, most of the consumed polyphenols remain in the gastrointestinal tract, where they then can exert inhibitory effects on enzymes involved in the degradation of saccharides, lipids, and proteins. While the inhibitory effects of phenolics on the digestion of energy-rich food components (saccharides and lipids) may be regarded as beneficial, primarily in weight-control diets, their inhibitory effects on the digestion of proteins are not desirable for the reason of reduced utilization of amino acids. The effect of polyphenols on protein digestion is reviewed in this article, with an emphasis on food processing methods to improve the antinutritive properties of polyphenols.

Mulberry leaf extract decreases digestion and absorption of starch in healthy subjects-A randomized, placebo-controlled, crossover study

PURPOSE

Mulberry (Morus alba L.) leaf tea has recently received much attention as a dietary supplement due to the wide range of putative health benefits, such as antidiabetic effects. Nevertheless, data evaluating its influence on carbohydrate metabolism in humans are scarce. The present study aims to investigate the effect of mulberry leaf extract supplementation on starch digestion and absorption in humans.

MATERIALS AND METHODS

The study comprised of 25 healthy subjects, aged 19-27 years. In all subjects, a starch 13C breath test was performed twice in a crossover and single blind design. Subjects were initially randomized to ingest naturally 13C-abundant cornflakes (50g cornflakes+100ml low fat milk) either with the mulberry leaf extract (36mg of active component-1-deoxynojirimycin) or the placebo and each subject received the opposite preparation one week later.

RESULTS

The cumulative percentage dose recovery was lower for the mulberry leaf extract test than for the placebo test (median [quartile distribution]: 13.9% [9.9-17.4] vs. 17.2% [13.3-20.6]; p=0.015). A significant decrease was detectable from minute 120 after the ingestion.

CONCLUSIONS

A single dose of mulberry leaf extract taken with a test meal decreases starch digestion and absorption. These findings could possibly be translated into everyday practice for improvement of postprandial glycemic control.

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.

Antidiabetic Effects of Tea

Diabetes mellitus (DM) is a chronic endocrine disease resulted from insulin secretory defect or insulin resistance and it is a leading cause of death around the world. The care of DM patients consumes a huge budget due to the high frequency of consultations and long hospitalizations, making DM a serious threat to both human health and global economies. Tea contains abundant polyphenols and caffeine which showed antidiabetic activity, so the development of antidiabetic medications from tea and its extracts is increasingly receiving attention. However, the results claiming an association between tea consumption and reduced DM risk are inconsistent. The advances in the epidemiologic evidence and the underlying antidiabetic mechanisms of tea are reviewed in this paper. The inconsistent results and the possible causes behind them are also discussed.

Improved Lipid Profile Associated with Daily Consumption of Tri-Sura-Phon in Healthy Overweight Volunteers: An Open-Label, Randomized Controlled Trial

Tri-Sura-Phon (TSP), a traditional Thai polyherbal formula renowned for its rejuvenating properties, is commonly used as a blood tonic. It comprises Cinnamomum bejolghota, Cinnamomum parthenoxylon, and Aquilaria crassna. The aim of this study is to evaluate the beneficial properties of TSP tea consumption on blood glucose regulation and serum lipid profiles of healthy overweight volunteers. This open-label, randomized controlled trial was conducted in 70 healthy overweight adults. Two groups of 35 subjects took a TSP infusion or a placebo (cornstarch) twice daily for 8 weeks. The blood glucose regulation, serum lipid profiles, BMI, and liver function tests of the subjects were determined at the baseline, 4th week, and endpoint (8th week). Significant decreases in the average fasting levels of total cholesterol (p = 0.013), triglyceride (p = 0.001), and low-density lipoprotein (LDL, p = 0.017) were observed in the TSP group at the 8th week compared to those at the baseline. The average HDL level in the TSP group at the beginning of the study was 65.2 mg/dL, and it increased significantly (p = 0.005) to 72.4 mg/dL after 8 weeks of TSP intake. This study showed that the intake of TSP tea as an antioxidant-rich beverage might be safe and improve lipid profiles in overweight adults.