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1.
ACS Omega ; 7(44): 40034-40041, 2022 Nov 08.
Article in English | MEDLINE | ID: mdl-36385823

ABSTRACT

p-Cresol (PC), a gut bacterial product of tyrosine catabolism, is recognized as a uremic toxin that has negative biological effects. Lowering the plasma PC level by manipulating the gut bacterial composition represents a promising therapeutic strategy in chronic kidney disease. This study was conducted to reveal whether epigallocatechin-3-gallate (EGCG) decreases plasma PC levels by limiting its bacterial production in a mouse model. The PC concentration in the samples was measured by high-performance liquid chromatography (HPLC) after treatments with sulfatase and ß-glucuronidase. The results showed that the addition of EGCG to the diet decreased the plasma and urinary concentrations of PC in a dose-dependent manner, with a statistically significant difference between the control group and the 0.2% EGCG group. However, once EGCG was enzymatically hydrolyzed to epigallocatechin (EGC) and gallic acid, such effects were lost almost completely. The addition of 0.2% EGCG in the diet was accompanied by a decreased abundance of Firmicutes at the phylum level and Clostridiales at the order level, which constitute a large part of PC produced from tyrosine. In conclusion, EGCG, not EGC, reduced plasma and urinary concentrations of PC in mice by suppressing its bacterial production with accompanying alteration of the relative abundance of PC producers.

2.
J Agric Food Chem ; 69(49): 14849-14855, 2021 Dec 15.
Article in English | MEDLINE | ID: mdl-34870993

ABSTRACT

(-)-Epigallocatechin-3-gallate (EGCG) undergoes auto-oxidation at physiological pH and therefore may be poorly absorbed in the intestine. Fructooligosaccharides (FOS), comprising a group of 1-kestose, nystose, and 1F-ß fructofuranosyl-nystose, are fermentable by gut bacteria and converted mainly into lactate. This study was conducted to determine whether dietary FOS may help to increase the plasma concentration of EGCG in rats by preventing it from auto-oxidation. Rats consumed an assigned diet, either a 0.3% (w/w) EGCG diet or an EGCG diet with additional 1, 3, or 5% (w/w) FOS, for 2 weeks. The results showed that the plasma concentration of EGCG was 0.21 ± 0.05 µM for the EGCG alone group, and it was significantly higher at 0.65 ± 0.12 µM for the EGCG plus 5% FOS group. Treatments with FOS resulted in a dose-dependent increase in the cecal level of lactate and brought the cecal pH down, with an accompanying alteration in the abundance of Lactobacillus and Collinsella. Because EGCG concentrations in the cecal digesta of rats fed the FOS-containing diet maintained comparatively high levels, FOS likely contributed to the protection of EGCG from auto-oxidation. In conclusion, FOS reduced the pH of the lumen of the intestine, kept EGCG intact to a certain degree, and consequently allowed EGCG to be taken into the blood circulation from the intestine.


Subject(s)
Catechin , Animals , Catechin/analogs & derivatives , Cecum , Diet , Oligosaccharides , Rats
3.
Food Sci Nutr ; 6(4): 728-735, 2018 Jun.
Article in English | MEDLINE | ID: mdl-29983934

ABSTRACT

Increasing evidence indicates that gut microbiota plays a critical role to maintain the host's health. The biological function of microbially produced short-chain fatty acids (SCFA) becomes the focus of attention. This study aimed to compare the effects of green tea extract (GTE) and black tea extract (BTE) on cecal levels of SCFA in rats. Rats consumed an assigned diet of either a control diet, a GTE diet (10 g/kg), or a BTE diet (10 g/kg), for 3 weeks. The dietary addition of GTE significantly reduced the concentrations of acetate and butyrate in cecal digesta compared to the control, but BTE showed an increased trend for a cecal pool. In the GTE group, a significant amount of undigested starch was excreted in feces, but BTE produced no effect. Interestingly, feces of rats fed the BTE diet contained higher bacterial 16S rRNA gene copy numbers for total eubacteria compared to the control diet. Taken together, treatments of the diets with GTE and BTE brought about a different degree of producing SCFA in rat cecum. BTE might advantageously stimulate more SCFA production than GTE by facilitating bacterial utilization of starch.

4.
Biosci Biotechnol Biochem ; 82(4): 636-646, 2018 Apr.
Article in English | MEDLINE | ID: mdl-29191128

ABSTRACT

Inhibition of excessive fructose intake in the small intestine could alleviate fructose-induced diseases such as hypertension and non-alcoholic fatty liver disease. We examined the effect of phytochemicals on fructose uptake using human intestinal epithelial-like Caco-2 cells which express the fructose transporter, GLUT5. Among 35 phytochemicals tested, five, including nobiletin and epicatechin gallate (ECg), markedly inhibited fructose uptake. Nobiletin and ECg also inhibited the uptake of glucose but not of L-leucine or Gly-Sar, suggesting an inhibitory effect specific to monosaccharide transporters. Kinetic analysis further suggested that this reduction in fructose uptake was associated with a decrease in the apparent number of cell-surface GLUT5 molecules, and not with a change in the affinity of GLUT5 for fructose. Lastly, nobiletin and ECg suppressed the permeation of fructose across Caco-2 cell monolayers. These findings suggest that nobiletin and ECg are good candidates for preventing diseases caused by excessive fructose intake.


Subject(s)
Catechin/analogs & derivatives , Flavones/pharmacology , Fructose/metabolism , Intestinal Mucosa/drug effects , Caco-2 Cells , Catechin/pharmacology , Cell Membrane Permeability/drug effects , Glucose Transporter Type 5/metabolism , Humans , Intestinal Mucosa/cytology , Intestinal Mucosa/metabolism , Kinetics , Phytochemicals/pharmacology
5.
J Agric Food Chem ; 63(36): 7952-7, 2015 Sep 16.
Article in English | MEDLINE | ID: mdl-26306898

ABSTRACT

There has been particular interest in the prebiotic-like effects of commonly consumed polyphenols. This study aimed to evaluate the effects of hesperidin (HD) and its aglycone hesperetin (HT), major flavonoids in citrus fruits, on the structure and activity of gut microbiota in rats. Rats ingested an assigned diet (a control diet, a 0.5% HT diet, or a 1.0% HD diet) for 3 weeks. Terminal restriction fragment length polymorphism analysis revealed that the proportion of Clostridium subcluster XIVa in the feces collected at the third week of feeding was significantly reduced by the HT diet: 19.8 ± 4.3% for the control diet versus 5.3 ± 1.5% for the HT diet (P < 0.01). There was a significant difference in the cecal pool of short-chain fatty acids (SCFA), the sum of acetic, propionic, and butyric acids, between the control diet (212 ± 71 µmol) and the HT diet (310 ± 51 µmol) (P < 0.05), whereas the HD diet exhibited no effects (245 ± 51 µmol). Interestingly, dietary HT resulted in a significant increase in the excretion of starch in the feces. HT, but not HD, might reduce starch digestion, and parts of undigested starch were utilized to produce SCFA by microbial fermentation in the large intestine.


Subject(s)
Cecum/metabolism , Fatty Acids, Volatile/metabolism , Feces/microbiology , Gastrointestinal Microbiome/drug effects , Hesperidin/pharmacology , Animals , Bacteria/classification , Bacteria/drug effects , Bacteria/genetics , Bacteria/isolation & purification , Cecum/drug effects , Cecum/microbiology , Male , Rats , Rats, Wistar
6.
J Nutr Sci Vitaminol (Tokyo) ; 60(3): 213-9, 2014.
Article in English | MEDLINE | ID: mdl-25078378

ABSTRACT

Alterations in gut microbiota composition offer insights that may be relevant for several chronic conditions, including obesity. This study aimed to evaluate the effect of (-)-epigallocatechin gallate (EGCG) on the modulation of gut microbiota and biomarkers of colonic fermentation end-products in rats. Rats were fed an assigned diet of either a control diet, a 0.3% (w/w) EGCG diet, or a 0.6% (w/w) EGCG diet for 4 wk. Compared to the control group, the addition of 0.6% EGCG to the diet brought about a significant increase in the starch and protein contents in the feces collected in the fourth week of feeding, but the relative weights of abdominal adipose tissues of rats were inversely suppressed. Host-specific bacterial community composition, as determined by terminal restriction fragment length polymorphism (T-RFLP) patterns for fecal 16S ribosomal RNA, showed a significant response in the reduced occupation of Clostridium spp. and an increased trend of Bacteroides by dietary supplementation with EGCG. The 0.6% EGCG diet also influenced the status of Bifidobacterium and Prevotella to a lesser extent. Interestingly, the cecum of rats fed the 0.6% EGCG diet contained lower levels of acetic and butyric acids, whereas EGCG had little influence on the cecal level of propionic acid. EGCG also reduced the cecal p-cresol concentration in a dose-dependent fashion. In conclusion, dietary EGCG affects the growth of certain species of gut microbiota in rats and is associated with the cecal pattern of short chain fatty acids which could be responsible for regulating energy metabolism in the body.


Subject(s)
Biomarkers/metabolism , Catechin/analogs & derivatives , Dietary Supplements , Gastrointestinal Tract/drug effects , Gastrointestinal Tract/microbiology , Microbiota , Acetic Acid/metabolism , Animals , Bifidobacterium/drug effects , Bifidobacterium/isolation & purification , Butyric Acid/metabolism , Catechin/administration & dosage , Clostridium/drug effects , Clostridium/isolation & purification , Cresols/metabolism , Feces/microbiology , Fermentation , Male , Organ Size , Prevotella/drug effects , Prevotella/isolation & purification , Rats , Rats, Wistar , Weight Gain/drug effects
7.
J Nutr Sci Vitaminol (Tokyo) ; 58(1): 45-9, 2012.
Article in English | MEDLINE | ID: mdl-23007066

ABSTRACT

This study was carried out to elucidate the structural advantage of a gallated form of tea catechin on modulating bioavailability of dietary starch in rats. Animal studies demonstrated that the addition of 0.5% (w/w) (-)-epigallocatechin gallate (EGCG) to the diet brought about a significant increase in the starch content in the feces collected for 2 d at the fourth week of feeding over that with the control diet. Of the gross starch that the rats consumed from their respective diets during the fecal collection period, 0.1% (for control diet) and 1.9% (for EGCG diet) were estimated to be excreted in the feces. However, such a significant increase in the fecal excretion of starch by the EGCG diet was lost by undergoing hydrolysis of EGCG to (-)-epigallocatechin (EGC) and gallic acid (GA). In vitro investigation also showed that EGCG inhibited porcine pancreatic α-amylase activity in a concentration-dependent fashion, whereas the hydrolyzed preparation (the mixture of EGC and GA) exhibited a lack of the inhibitory activity for α-amylase. The modification of dietary starch digestion by inhibiting intestinal α-amylase activity with EGCG may be responsible at least in part for increasing fecal output of starch in rats. Thus, the attachment of a galloyl moiety to the tea flavan-3-ol skeleton may be of key importance for reducing intestinal digestion of dietary starch in rats.


Subject(s)
Catechin/analogs & derivatives , Feces/chemistry , Starch/metabolism , Tea/chemistry , Animals , Catechin/metabolism , Catechin/pharmacology , Dietary Carbohydrates/metabolism , Intestinal Mucosa/metabolism , Intestines/drug effects , Male , Rats , Rats, Wistar , Statistics, Nonparametric , alpha-Amylases/antagonists & inhibitors , alpha-Amylases/metabolism
8.
J Nutr Sci Vitaminol (Tokyo) ; 55(5): 447-51, 2009.
Article in English | MEDLINE | ID: mdl-19926934

ABSTRACT

Much attention has been paid to the beneficial health effect of tea catechins as one of the effective strategies to prevent obesity. The current study was carried out to investigate the role of tea catechins on the utilization of dietary energy sources in rats. The addition of 1% (w/w) tea catechins, mostly in gallate forms, to the diet brought about significant reductions in body weight gains and abdominal adipose tissue weights after 4-wk feeding periods compared to the control. A 2-d output of feces collected at the third week of feeding was significantly increased by a tea catechin diet (average dry weight+/-SD of 7.2+/-1.5 g) over that with a control diet (3.8+/-0.4 g). Only 0.1% of ingested starch appeared in the feces of rats fed the control diet, whereas 4.8% was excreted in the feces of the tea catechin group. Moreover, both apparent digestibility values for lipid and protein in the rats fed tea catechins were also lower than those of the control, suggesting that tea catechins increased the fecal excretion of these energy nutrients. Of the gross energy that the rats consumed from their respective diets during the fecal collection period, 1.6% (for control diet) and 5.8% (for tea catechin diet) were estimated to be excreted in feces. The energy loss originating from carbohydrate should contribute to the overall amount of energy in the feces, followed by protein. Intake of tea catechins suppressed the intestinal absorption of energy nutrients via the inhibition of digestive enzymes, which may at least partially influence the body fat reduction by tea catechins.


Subject(s)
Anti-Obesity Agents/pharmacology , Camellia sinensis/chemistry , Catechin/pharmacology , Feces/chemistry , Intestinal Absorption/drug effects , Obesity/prevention & control , Plant Extracts/pharmacology , Abdominal Fat/drug effects , Adipose Tissue , Animals , Anti-Obesity Agents/therapeutic use , Beverages , Body Weight/drug effects , Catechin/therapeutic use , Diet , Dietary Carbohydrates/metabolism , Dietary Carbohydrates/pharmacokinetics , Dietary Fats/pharmacokinetics , Dietary Proteins/pharmacokinetics , Digestion/drug effects , Energy Intake/drug effects , Male , Organ Size/drug effects , Phytotherapy , Plant Extracts/therapeutic use , Rats , Rats, Wistar , Starch/analysis , Starch/metabolism , Starch/pharmacokinetics , Weight Gain/drug effects
9.
J Agric Food Chem ; 57(15): 7131-6, 2009 Aug 12.
Article in English | MEDLINE | ID: mdl-19722586

ABSTRACT

Administration of black-tea polyphenols (BTP) at 100 and 200 mg/kg of body weight in rats suppressed postprandial hypertriacylglycerolemia in a dose-dependent manner. Administration of BTP also suppressed lymphatic recovery of (14)C-trioleoylglycerol in rats that were cannulated in the thoracic duct. BTP dose-dependently inhibited the activity of pancreatic lipase in vitro with an IC50 of 0.254 mg/mL. When purified theaflavins, which are components of BTP, were used, theaflavins with galloyl moieties, but not those without galloyl moiety, inhibited the activity of pancreatic lipase. Theaflavin-3,3'-digallate (TFDG) was more effective in inhibiting the activity of pancreatic lipase than epigallocatechin gallate (EGCG), epicatechin gallate (ECG), and a mixture of EGCG and ECG. BTP and TFDG had a similar effect in inhibiting the activity of pancreatic lipase when the total polyphenol amount was adjusted to the same. BTP had no effect on micellar solubility of hydrolysis products of triacylglycerol. These results suggest that BTP suppressed postprandial hypertriacylglycerolemia by reducing triacylglycerol absorption via the inhibition of pancreatic lipase activity.


Subject(s)
Dietary Fats/metabolism , Flavonoids/metabolism , Hypertriglyceridemia/metabolism , Lymph/metabolism , Phenols/metabolism , Tea/chemistry , Animals , Biological Transport , Camellia sinensis/chemistry , Flavonoids/administration & dosage , Flavonoids/chemistry , Humans , Hypertriglyceridemia/drug therapy , Male , Phenols/administration & dosage , Phenols/chemistry , Polyphenols , Postprandial Period , Rats , Rats, Sprague-Dawley , Rats, Wistar , Tea/metabolism
10.
J Agric Food Chem ; 53(26): 9885-9, 2005 Dec 28.
Article in English | MEDLINE | ID: mdl-16366670

ABSTRACT

Accurate monitoring of tea catechins in biological samples might provide a means of better evaluation of their benefits. The aim of the present study was to develop a rapid method for extracting tea catechins from human plasma samples with a solid-phase extraction technique and to subsequently measure their concentrations using an HPLC system. A human plasma sample spiked with known concentrations of the analyte standards was passed through a Waters Oasis HLB cartridge. After repeated washing, tea catechins were eluted with 70% dimethylformamide containing 0.1% phosphoric acid, and the resulting eluate was injected into an HPLC system. Analytes were separated on a reverse-phase C18 column using an isocratic mobile phase and detected electrochemically. The coefficient of variation for inter- and intraday reproducibility was less than 5.0% and 6.4%, respectively. Linearity was established for the concentration range of 0.01-1.0 microM. The method was successfully applied to measure tea catechin concentrations in the plasma of two healthy subjects who received a single ingestion of a green tea beverage. The proposed method enables the rapid and accurate quantitation of plasma tea catechins and might prove useful for the evaluation of beneficial health effects of tea consumption.


Subject(s)
Catechin/blood , Tea/chemistry , Adult , Catechin/pharmacokinetics , Chromatography, High Pressure Liquid , Humans , Indicators and Reagents , Male , Pilot Projects , Reference Standards , Reproducibility of Results
11.
Biosci Biotechnol Biochem ; 69(12): 2455-8, 2005 Dec.
Article in English | MEDLINE | ID: mdl-16377909

ABSTRACT

Tea catechins are known to be epimerized by heat treatment. The effect of heat-epimerized tea catechins on serum cholesterol concentration was compared with that of green tea catechins. Our observations strongly suggest that both tea catechins and heat-epimerized tea catechins lower serum cholesterol concentration by inhibiting cholesterol absorption in the intestine. There was no differential effect between the two catechin preparations.


Subject(s)
Anticholesteremic Agents , Catechin/chemistry , Catechin/pharmacology , Cholesterol, Dietary/pharmacology , Cholesterol/blood , Tea/chemistry , Animals , Body Weight/drug effects , Cholesterol, HDL/blood , Eating/drug effects , Feces/chemistry , Hot Temperature , Intestinal Absorption/drug effects , Lipids/blood , Male , Rats , Rats, Sprague-Dawley , Stereoisomerism
12.
Lipids ; 40(8): 849-53, 2005 Aug.
Article in English | MEDLINE | ID: mdl-16296404

ABSTRACT

Tea is a widely consumed beverage throughout the world. We assessed the antioxidant activity of six teas, including the aqueous extracts of green tea and oolong tea (Camellia sinensis), tochu (Eucommia ulmoides), Gymnema sylvestre, Japanese mugwort (Artemisia princeps), and barley (Hordeum vulgare), against 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and LDL oxidation, and examined the association of LDL oxidizability with the plasma catechin levels in 10 healthy volunteers with a single dose of 5 g green tea powder. In vitro, the inhibitory effects of DPPH radicals and LDL oxidation were found to be strongest in the extract of green tea and weakest in that of barley. After the ingestion of green tea powder, the lag time increased from basal 52.2 +/- 4.1 to 60.3 +/- 4.2 min at 1 h and 59.5 +/- 4.1 min at 2 h, and then returned to the baseline lag time (51.9 +/- 1.4 at 4 h and 52.1 +/- 4.7 min at 6 h). Regarding the plasma catechin levels, epigallocatechingallate and epicatechingallate significantly increased from basal 3.7 +/- 1.3 and 0.8 +/- 0.8 ng/mL to 65.7 +/- 11.6 and 54.6 +/- 12.6 ng/mL at 1 h, and 74.4 +/- 18.6 and 49.4 +/- 7.1 ng/mL at 2 h, respectively. Green tea therefore showed the strongest antioxidant activity among the six different teas, and the inhibitory effects of green tea on LDL oxidation depended on the plasma catechin levels.


Subject(s)
Antioxidants/pharmacology , Free Radical Scavengers/pharmacology , Lipoproteins, LDL/metabolism , Tea/chemistry , Oxidation-Reduction , Plant Extracts/pharmacology , Reference Values
13.
Biosci Biotechnol Biochem ; 69(7): 1288-91, 2005 Jul.
Article in English | MEDLINE | ID: mdl-16041132

ABSTRACT

Tea has long been believed to be a healthy beverage, and its beneficial effects are almost all attributed to catechins. The effect of catechins on postprandial hypertriglyceridemia in rats was investigated in this study. A lipid emulsion administered orally to rats with (-)-epigallocatechin gallate at a dose of 100 mg/kg resulted in the increase in plasma triacylglycerol being significantly inhibited after 1 and 2 h compared to the case without (-)-epigallocatechin gallate. The effect of (-)-epigallocatechin was weaker than that of (-)-epigallocatechin gallate. A tea extract (THEA-FLAN 90S), mainly composed of catechins with a galloyl moiety, dose-dependently suppressed postprandial triacylglycerol after the administration of a lipid emulsion at doses of 50-200 mg/kg. The administration of the tea extract alone at a dose of 200 mg/kg had no effect on the plasma triacylglycerol level. These results strongly suggest that catechins with a galloyl moiety would be promising agents for suppressing dietary fat absorption through the small intestine.


Subject(s)
Catechin/analogs & derivatives , Hypertriglyceridemia/prevention & control , Tea/chemistry , Animals , Catechin/administration & dosage , Catechin/chemistry , Catechin/pharmacology , Dose-Response Relationship, Drug , Fatty Acids, Nonesterified/blood , Hypertriglyceridemia/blood , Male , Postprandial Period , Rats , Rats, Wistar , Time Factors , Triglycerides/blood
14.
Br J Nutr ; 93(4): 543-7, 2005 Apr.
Article in English | MEDLINE | ID: mdl-15946418

ABSTRACT

Epidemiological surveys suggest that a higher intake of tea may be associated with a lower risk of CHD. There is accumulating evidence that postprandial lipaemia makes a substantial contribution to the incidence of CHD. Our aim was, therefore, to evaluate the effect of tea catechins (major ingredients in green tea) on postprandial lipid responses in human subjects after the consumption of test meals. In a randomized triple-crossover design, nine male subjects with mild or borderline hypertriacylglycerolaemia consumed 10 (control), 224 (moderate dose) and 674 mg (high dose) of the assigned tea catechins three times each along with a standardized light meal consisting of a piece of bread spread with 20 g butter. Plasma lipids were measured in the fasting state and 1, 2, 3, 4 and 6 h after consuming the light meal. Results showed that, compared with the control, moderate and high doses of tea catechins reduced the incremental area under the plasma triacylglycerol curves by 15.1 and 28.7%, respectively. Next, the rapid elevation of remnant-like particle cholesterol was significantly inhibited by a high dose of tea catechins 2 h after consuming the light meal (P<0.01). In the range of tea catechin dosages, no significant differences were observed in the postprandial responses for plasma total cholesterol or NEFA at any time point. In conclusion, this trial demonstrated that tea catechins attenuated the postprandial increase in plasma triacylglycerol levels following a fat load. These results may provide evidence for one of the possible mechanisms involved in lowering the incidence of CVD, and may prove useful in further studies on the beneficial health effects of tea drinking.


Subject(s)
Catechin/administration & dosage , Lipids/blood , Tea , Adult , Cholesterol/blood , Cross-Over Studies , Humans , Male , Middle Aged , Postprandial Period , Triglycerides/blood
15.
J Nutr ; 135(2): 155-9, 2005 Feb.
Article in English | MEDLINE | ID: mdl-15671206

ABSTRACT

Tea catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG), have been shown to be epimerized to (-)-catechin (C), (-)-gallocatechin (GC), (-)-catechin gallate (CG), and (-)-gallocatechin gallate (GCG), respectively, during heat treatment. In this study, we examined the effect of tea catechins rich in ECG and EGCG and heat-treated tea catechins rich in CG and GCG on postprandial hypertriacylglycerolemia in rats. Both tea catechins and heat-treated tea catechins suppressed postprandial hypertriacylglycerolemia. Lymphatic recovery of (14)C-trioleoylglycerol in rats cannulated in the thoracic duct was delayed by the administration of tea catechins and heat-treated tea catechins. Tea catechins and heat-treated tea catechins had the same effect on all variables tested. These catechin preparations dose-dependently inhibited the activity of pancreatic lipase in vitro. When purified catechins were used, only those with a galloyl moiety inhibited the activity of pancreatic lipase. These results suggest that catechins with a galloyl moiety suppress postprandial hypertriacylglycerolemia by slowing down triacylglycerol absorption through the inhibition of pancreatic lipase. Because postprandial hypertriacylglycerolemia is a risk factor for coronary heart disease, our results suggest that catechins with a galloyl moiety may prevent this disease.


Subject(s)
Antioxidants/pharmacology , Antioxidants/pharmacokinetics , Catechin/analogs & derivatives , Catechin/pharmacology , Catechin/pharmacokinetics , Dietary Fats/metabolism , Hypertriglyceridemia/prevention & control , Lymphatic System/physiology , Tea , Animals , Biological Transport/drug effects , Lymphatic System/drug effects , Male , Models, Animal , Rats , Rats, Wistar
16.
J Ethnopharmacol ; 93(2-3): 391-5, 2004 Aug.
Article in English | MEDLINE | ID: mdl-15234783

ABSTRACT

Xanthine oxidase (XOD) is a key enzyme playing a role in hyperuricemia, catalyzing the oxidation of hypoxanthine to xanthine and then to uric acid. This study aimed to identify the XOD inhibitors from the leaves of Lagerstroemia speciosa (L.) Pers. (Lythraceae), which was traditionally used as a folk medicine in the Philippines. Using a bioassay-guided fractionation technique, two active compounds were isolated from the aqueous extracts of the Lagerstroemia speciosa leaves, namely valoneic acid dilactone (VAD) and ellagic acid (EA). The result demonstrated that the XOD-inhibitory effect of VAD was a stronger than that of allopurinol, a clinical drug used for XOD inhibitor, with a non-competitive mode for the enzyme with respect to xanthine as the substrate. These results may explain and support the dietary use of the aqueous extracts from Lagerstroemia speciosa leaves for the prevention and treatment of hyperuricemia.


Subject(s)
Enzyme Inhibitors/pharmacology , Lagerstroemia , Phytotherapy , Plant Extracts/pharmacology , Xanthine Oxidase/antagonists & inhibitors , Allopurinol/administration & dosage , Allopurinol/pharmacology , Allopurinol/therapeutic use , Enzyme Inhibitors/administration & dosage , Enzyme Inhibitors/therapeutic use , Gout Suppressants/administration & dosage , Gout Suppressants/pharmacology , Gout Suppressants/therapeutic use , Humans , Hyperuricemia/prevention & control , Plant Extracts/administration & dosage , Plant Extracts/therapeutic use , Plant Leaves
17.
J Agric Food Chem ; 51(23): 6893-8, 2003 Nov 05.
Article in English | MEDLINE | ID: mdl-14582992

ABSTRACT

There is great interest in the nutritional potential of (-)-epicatechin, a common polyphenolic constituent of many foods and beverages, because of its potent antioxidant capacity. To better evaluate the biological role of (-)-epicatechin, we studied the urinary excretion of 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone, a ring-fission metabolite of (-)-epicatechin by intestinal microflora, in rats as well as its antioxidant activity in vitro. The method for measuring the urinary levels of (-)-epicatechin and 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone was based on the enzymatic hydrolysis of beta-glucuronidase and sulfatase, and was subsequently determined by HPLC coupled to an electrochemical detector. Following administration of (-)-epicatechin at doses of 0, 20, 40, and 80 mumol per rat, (-)-epicatechin and 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone were excreted into the urine within 24 h in a dose-dependent manner. Urinary 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone was mostly in the conjugated form, with a higher ratio of conjugation than (-)-epicatechin. We assessed the relative antioxidant potentials for scavenging radicals in the aqueous phase as expressed in the Trolox equivalent antioxidant capacity (TEAC). The results demonstrated that the degradation of (-)-epicatechin into 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone attenuated the antioxidant ability of the former. However, 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone showed stronger antioxidant activity than l-ascorbic acid. These results led us to suppose that 5-(3',4'-dihydroxyphenyl)-gamma-valerolactone, a microbial metabolite of (-)-epicatechin, circulating in the body may also at least be biologically active in terms of contributing to its combined antioxidant effect.


Subject(s)
Antioxidants/pharmacology , Catechin/metabolism , Lactones/pharmacology , Lactones/urine , Animals , Ascorbic Acid/pharmacology , Catechin/urine , Chromans/chemistry , Chromatography, High Pressure Liquid , Male , Rats , Rats, Wistar
18.
Biochim Biophys Acta ; 1620(1-3): 47-53, 2003 Mar 17.
Article in English | MEDLINE | ID: mdl-12595072

ABSTRACT

The distribution of theanine-degrading activity in Wistar rats was examined and this activity was detected only in the kidney. Judging from polyacrylamide gel electrophoresis, theanine-degrading enzyme from rat kidney was purified almost to homogeneity. Theanine-degrading activity was co-purified with glutaminase activity, and the relative activity for theanine was about 85% of that for L-glutamine throughout purification. Substrate specificity of purified enzyme preparation coincided well with the data of phosphate-independent glutaminase [EC 3.5.1.2], which had been previously reported. It was very curious that gamma-glutamyl methyl and ethyl esters were more effectively hydrolyzed than theanine and L-glutamine, in view of relative activity and K(m) value. It was suggested that gamma-glutamyl moiety in theanine molecule was transferred to form gamma-glutamylglycylglycine with relative ease in the presence of glycylglycine. On the other hand, purified phosphate-dependent glutaminase did not show theanine-degrading activity at all. Thus, it was concluded that theanine was hydrolyzed by phosphate-independent glutaminase in kidney and suggested that, as for the metabolic fate of theanine, its glutamyl moiety might be transferred by means of gamma-glutamyl transpeptidase reaction to other peptides in vivo.


Subject(s)
Glutamates/metabolism , Glutaminase/metabolism , Kidney/enzymology , Animals , Chromatography, Thin Layer , Electrophoresis, Polyacrylamide Gel , Ethylamines/metabolism , Glutamic Acid/metabolism , Glutaminase/chemistry , Glutaminase/isolation & purification , Glycylglycine , Isoenzymes/metabolism , Phosphates/chemistry , Rats , Rats, Wistar , Substrate Specificity , gamma-Glutamyltransferase/metabolism
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