Gastric H+, K(+)-ATPase inhibition by catechins

Tea Plant (Camellia sinensis): A Current Update on Use in Diabetes, Obesity, and Cardiovascular Disease

The tea plant (C. sinensis) has traditionally been consumed worldwide as "tea" for its many health benefits, with the potential for the prevention and therapy of various conditions. Regardless of its long history, the use of tea plants in modern times seems not to have changed much, as the beverage remains the most popular form. This review aimed to compile scientific information about the role and action of tea plants, as well as their status concerning clinical applications, based on the currently available evidence, with a focus on metabolic syndrome, mainly covering obesity, diabetes, and cardiovascular disease. It has been recognized that these diseases pose a significant threat to public health, and the development of effective treatment and prevention strategies is necessary but still challenging. In this article, the potential benefits of tea plants and their derived bioactive components (such as epigallocatechin-3-gallate) as anti-obesity, anti-diabetic, and anti-cardiovascular agents are clearly shown and emphasized, along with their mechanisms of action. However, according to the status of the clinical translation of tea plants, particularly in drug development, more substantial efforts in well-designed, randomized, controlled trials are required to expand their applications in treating the three major metabolic disorders and avoiding the toxicity caused by overconsumption.

Treatment of Gastrointestinal Disorders-Plants and Potential Mechanisms of Action of Their Constituents

The worldwide prevalence of gastrointestinal diseases is about 40%, with standard pharmacotherapy being long-lasting and economically challenging. Of the dozens of diseases listed by the Rome IV Foundation criteria, for five of them (heartburn, dyspepsia, nausea and vomiting disorder, constipation, and diarrhoea), treatment with herbals is an official alternative, legislatively supported by the European Medicines Agency (EMA). However, for most plants, the Directive does not require a description of the mechanisms of action, which should be related to the therapeutic effect of the European plant in question. This review article, therefore, summarizes the basic pharmacological knowledge of synthetic drugs used in selected functional gastrointestinal disorders (FGIDs) and correlates them with the constituents of medicinal plants. Therefore, the information presented here is intended as a starting point to support the claim that both empirical folk medicine and current and decades-old treatments with official herbal remedies have a rational basis in modern pharmacology.

Evaluation of gastroprotective and ulcer healing activities of yellow mombin juice from Spondias mombin L

Spondias mombin L. (yellow mombin) is a tree with a nutritional fruit that is commonly consumed in the North and Northeast of Brazil, as the juice of its pulp is rich in antioxidant compounds. This study aimed to investigate the gastroprotective and ulcer healing activities of yellow mombin juice (YMJ) in Wistar rats, and to elucidate the possible involved mechanisms. Phytochemical characterization of the lyophilized fruit juice was performed by high-performance liquid chromatography (HPLC). The gastroprotective activity of YMJ was investigated in ethanol (25, 50, and 100% YMJ) and indomethacin (100% YMJ) models of acute gastric ulcer in rats. Then, the effect of YMJ on mucus production and gastric secretions, and the involvement of non-protein sulfhydryl groups and prostaglandins in the gastroprotective process were examined. Moreover, the ulcer healing effect of YMJ was investigated in a model of acetic acid-induced chronic ulcer through histological and immunohistochemical analyses. HPLC results identified the presence of epicatechin (7.1 ± 1.6 μg/mL) and quercetin (17.3 ± 2.5 μg/mL) in YMJ. Ethanol-induced gastric lesions were inhibited by YMJ (25, 50, and 100%) by 42.42, 45.09, and 98.21% respectively, and indomethacin-induced lesions were inhibited by YMJ (100%) by 58.96%, compared to control group. Moreover, YMJ reduced gastric content and total acidy by 57.35 and 71.97%, respectively, compared to the control group. Treatment with YMJ also promoted healing of chronic ulcer, regeneration of the gastric mucosa, and restoration of mucus levels in glandular cells, as confirmed by histological analysis. It also increased cellular proliferation, as demonstrated by high reactivity to Ki-67 and bromodeoxyuridine. In conclusion, YMJ was found to possess gastroprotective and ulcer healing activities that are correlated to its antisecretory action. These results support the commercial exploration of YMJ as a functional food.

Antidiarrhoeal properties of Syzygium guineense leaf extract and identification of chemical constituents in its active column fractions

Background Syzygium guineense (Myrtaceae) has been used in traditional medicine against various ailments, including diarrhoea. This study was conducted to scientifically evaluate the antidiarrheal effects of S. guineense extract and fractions. Methods An ethanol extract of S. guineense leaves was prepared and tested for its effect on small intestinal propulsion in mice and castor oil-induced fluid accumulation in rats. The extract was also evaluated for its effect on itopride-induced small intestine propulsion in mice. Column fractions were also investigated in rats and sub-fractions were tested for activity on spontaneous contractions of isolated rabbit jejunum. Results The results showed that the extract significantly (p<0.05) inhibited intrinsic small intestinal propulsion and itopride-induced propulsive activity, similar to atropine (0.3 mg/kg) although its inhibitory effect against castor oil-induced intestinal fluid accumulation and diarrhoea was statistically insignificant (p>0.05). Column separation yielded 14 fractions, with three fractions producing significant (p<0.001) inhibition of small intestinal propulsion. Sub-fractions 1, 7 and 16 obtained from an active column fraction also exhibited relaxant effects on isolated rabbit jejunum. Spectral analysis (proton, 13C NMR) of sub-fractions 7 and 16 revealed the presence of betulinic acid, ursolic acid, oleanolic acid in 7 and a mixture of luteolin and friedelane-type triterpenes in 16. Conclusions These findings provide scientific evidence that S. guineense leaf extract possess antidiarrhoeal activity and may be potentially beneficial in treatment diarrhoeal disease. The identified compounds may also be implicated in its antidiarrhoeal effects.

Contribution of Secondary Metabolites to the Gastroprotective Effect of Aqueous Extract of Ximenia americana L. (Olacaceae) Stem Bark in Rats

Ximenia americana L. (Olacaceae) is used in ethnomedicine as cicatrizant and for the treatment of gastric disorders. This study identified the chemical constituents of the aqueous extract of X. americana (XaAE) and evaluated its antiulcerogenic activity. After lyophilization, XaAE was analyzed by liquid chromatography-mass spectrometry (LC-MS) and its antiulcerogenic effect was evaluated in acute gastric lesions induced by ethanol, acidified ethanol, and indomethacin. Antisecretory action, mucus production and the participation of sulfhydryl groups (-SH) and nitric oxide (NO) were also investigated. The chromatographic analysis identified procyanidins B and C and catechin/epicatechin as major compounds. Oral administration of XaAE (100, 200 and 400 mg/kg) inhibited the gastric lesions induced by ethanol (76.1%, 77.5% and 100%, respectively), acidified ethanol (44.9%, 80.6% and 94.9%, respectively) and indomethacin (56.4%, 52.7% and 64.9%, respectively). XaAE reduced gastric contents and acidity (51.4% and 67.7%, respectively) but did not alter the production of gastric mucus. The reduction of the -SH and NO groups promoted by N-ethylmaleimide (NEM) and Nω-nitro-l-arginine-methyl-ester (L-NAME) respectively, reduced the gastroprotective effect of XaAE. In conclusion, XaAE has gastroprotective activity mediated in part by -SH, NO and antisecretory activity. This antiulcer action was initially correlated to its major constituents, procyanidins B and C and catechin/epicatechin.

Phytochemicals enhance antioxidant enzyme expression to protect against NSAID-induced oxidative damage of the gastrointestinal mucosa

The gastrointestinal (GI) mucosa provides the first protective barrier for digested food and xenobiotics, which are easily attacked by toxic substances. Nonsteroidal anti-inflammatory drugs, including aspirin, diclofenac, indomethacin, and ketoprofen, are widely used in clinical medicine, but these drugs may cause oxidative stress, leading to GI damage such as ulcers. Lansoprazol, omeprazole, and other clinical drugs are widely used to treat duodenal and gastric ulcers and have been shown to have multiple biological functions, such as antioxidant activity and the ability to upregulate antioxidant enzymes in vivo. Therefore, the reduction of oxidative stress may be an effective curative strategy for preventing and treating nonsteroidal anti-inflammatory drug induced ulcers of the GI mucosa. Phytochemicals, such as dietary phenolic compounds, phenolic acids, flavan-3-ols, flavonols, flavonoids, gingerols, carotenes, and organosulfur, are common antioxidants in fruits, vegetables, and beverages. A large amount of evidence has demonstrated that natural phytochemicals possess bioactivity and potential health benefits, such as antioxidant, anti-inflammatory, and antibacterial benefits, and they can prevent digestive disease processes. In this review, we summarize the literature on phytochemicals with biological effects, such as angiogenic, antioxidant, antiapoptotic, anti-inflammatory, and antiulceration effects, and their related mechanisms are also discussed.

Role of dietary polyphenols in the management of peptic ulcer

Peptic ulcer disease is a multifactorial and complex disease involving gastric and duodenal ulcers. Despite medical advances, the management of peptic ulcer and its complications remains a challenge, with high morbidity and death rates for the disease. An accumulating body of evidence suggests that, among a broad reach of natural molecules, dietary polyphenols with multiple biological mechanisms of action play a pivotal part in the management of gastric and duodenal ulcers. The current review confirmed that dietary polyphenols possess protective and therapeutic potential in peptic ulcer mediated by: improving cytoprotection, re-epithelialization, neovascularization, and angiogenesis; up-regulating tissue growth factors and prostaglandins; down-regulating anti-angiogenic factors; enhancing endothelial nitric oxide synthase-derived NO; suppressing oxidative mucosal damage; amplifying antioxidant performance, antacid, and anti-secretory activity; increasing endogenous mucosal defensive agents; and blocking Helicobacter pylori colonization associated gastric morphological changes and gastroduodenal inflammation and ulceration. In addition, anti-inflammatory activity due to down-regulation of proinflammatory cytokines and cellular and intercellular adhesion agents, suppressing leukocyte-endothelium interaction, inhibiting nuclear signaling pathways of inflammatory process, and modulating intracellular transduction and transcription pathways have key roles in the anti-ulcer action of dietary polyphenols. In conclusion, administration of a significant amount of dietary polyphenols in the human diet or as part of dietary supplementation along with conventional treatment can result in perfect security and treatment of peptic ulcer. Further well-designed preclinical and clinical tests are recommended in order to recognize higher levels of evidence for the confirmation of bioefficacy and safety of dietary polyphenols in the management of peptic ulcer.

Flavonoids: chemical properties and analytical methodologies of identification and quantitation in foods and plants

Flavonoids have been recognised as one of the largest and most widespread groups of plant secondary metabolites, with marked antioxidant properties. The general name flavonoid refers to a class of more than 6500 molecules based upon a 15-carbon skeleton. In this paper a general overview of flavonoids, their classification, structures and analytical methods for their determination is presented.

1-(2-Hydr-oxy-5-methyl-phen-yl)-3-(3-methylthiophen-2-yl)prop-2-en-1-one

In the structure of the title compound, C₁₅H₁₄O₂S, the benzene ring is nearly coplanar with the thio­phene ring. The hydroxy group substituted at C2 position is in an antiperi­planar conformation with respect to the phenyl ring. The crystal structure exhibits weak intramolecular O—H⋯O hydrogen bonding.

Inhibition of gastric acid secretion by a standardized aqueous extract of Cecropia glaziovii Sneth and underlying mechanism

Cecropia glazioui Sneth (Cecropiaceae) is used in folk medicine in tropical and subtropical Latin America as cardiotonic, diuretic, hypotensive, anti-inflammatory and anti-asthmatic. The hypotensive/antihypertensive activity of the plant aqueous extract (AE) and isolated butanolic fraction (BuF) has been confirmed and putatively related to calcium channels blockade in vascular smooth musculature [Lapa, A.J., Lima-Landman, M.T.R., Cysneiros, R.M, Borges, A.C.R., Souccar, C., Barreta, I.P., Lima, T.C.M., 1999. The Brazilian folk medicine program to validate medicinal plants - a topic in new antihypertensive drug research. In: Hostettman, K., Gupta, M.P., Marston, A. (Eds.), Proceedings Volume, IOCD/CYTED Symposium, Panamá City, Panamá, 23-26 February 1997. Chemistry, Biological and Pharmacological Properties of Medicinal Plants from the Americas. Harwood Academic Publishers, Amsterdam, pp. 185-196; Lima-Landman, M.T., Borges, A.C., Cysneiros, R.M., De Lima, T.C., Souccar, C., Lapa, A.J., 2007. Antihypertensive effect of a standardized aqueous extract of Cecropia glaziovii Sneth in rats: an in vivo approach to the hypotensive mechanism. Phytomedicine 14, 314-320]. Bronchodilation and antidepressant-like activities of both AE and BuF have been also shown [Delarcina, S., Lima-Landman, M.T., Souccar, C., Cysneiros, R.M., Tanae, M.M., Lapa, A.J., 2007. Inhibition of histamine-induced bronchospasm in guinea pigs treated with Cecropia glaziovi Sneth and correlation with the in vitro activity in tracheal muscles. Phytomedicine 14, 328-332; Rocha, F.F., Lima-Landman, M.T., Souccar, C., Tanae, M.M., De Lima, T.C., Lapa, A.J., 2007. Antidepressant-like effect of Cecropia glazioui Sneth and its constituents -in vivo and in vitro characterization of the underlying mechanism. Phytomedicine 14, 396-402]. This study reports the antiulcer and antisecretory gastric acid activities of the plant AE, its BuF and isolated compounds with the possible mechanism involved. Both AE and BuF were assayed on gastric acid secretion of pylorus-ligated mice, on acute models of gastric mucosal lesions, and on rabbit gastric H(+), K(+)-ATPase preparations. Intraduodenal injection of AE or BuF (0.5-2.0g/kg, i.d) produced a dose-related decrease of the basal gastric acid secretion in 4-h pylorus-ligated mice. At 1.0g/kg, BuF decreased the volume (28%) and total acidity (33%) of the basal acid secretion, and reversed the histamine (2.5mg/kg, s.c.)- or bethanecol (1.0mg/kg, s.c.)-induced acid secretion to basal values, indicating inhibition of the gastric proton pump. Pretreatment of mice with the BuF (0.05-0.5g/kg, p.o.) protected against gastric mucosal lesions induced by 75% ethanol, indomethacin (30mg/kg, s.c.) or restraint at 4 degrees C. BuF also decreased the gastric H(+), K(+)-ATPase activity in vitro proportionately to the concentration (IC(50)=58.8microg/ml). The compounds isolated from BuF, consisting mainly of cathechins, procyanidins and flavonoids [Tanae, M.M., Lima-Landman, M.T.R., De Lima, T.C.M., Souccar, C., Lapa, A.J., 2007. Chemical standardization of the aqueous extract of Cecropia glaziovii Sneth endowed with antihypertensive, bronchodilator, antacid secretion and antidepressant-like activities. Phytomedicine 14, 309-313], inhibited the in vitro gastric H(+), K(+)-ATPase activity at equieffective concentrations to that of BuF. The results indicate that C. glazioui constituents inhibit the gastric proton pump; this effect may account for the effective antisecretory and antiulcer activities of the standardized plant extract.

Flavonoid-rich fraction of Maytenus ilicifolia Mart. ex. Reiss protects the gastric mucosa of rodents through inhibition of both H+,K+ -ATPase activity and formation of nitric oxide

Maytenus ilicifolia Mart. ex. Reissek (Celastraceae), a medicinal plant known in Brazil as "espinheira-santa" is commonly used to treat gastric disorders. The effect of the flavonoid-rich fraction separated from the leaves was evaluated for its gastroprotective properties and the mechanism(s) involved in this activity. Intraperitoneal administration of the flavonoid-rich fraction potently protected rats from experimentally induced chronic (ED(50)=79 mg/kg) and acute gastric lesions by ethanol (ED(50)=25mg/kg) and indomethacin (ED(50)=4 mg/kg) without altering the decreased amount of cytoprotective glutathione and mucus amount in the injured gastric mucosa. A potent reduction of gastric acid hypersecretion (ED(50)=7 mg/kg, i.p.) was accompanied by a reduction of nitric oxide release (ED(50)=1.6 mg/kg, i.p.) in the gastric secretion of 2h pylorus ligated rats which suggests an important role for nitric oxide-dependent mechanisms. Inhibition of gastric acid secretion in vivo was correlated with the in vitro inhibition of rabbit gastric H(+),K(+)-ATPase activity (IC(50)=41 microg/mL). Chemical investigation of the fraction showed galactitol (25%), epicatechin (3.1%) and catechin (2%) as the majoritary components. Collectively, the results show that the flavonoid-rich fraction of Maytenus ilicifolia potently protects animals from gastric lesions with high potency through inhibition of gastric acid secretion.

Inhibition of the gastric H+,K+ -ATPase by plectrinone A, a diterpenoid isolated from Plectranthus barbatus Andrews

This work assessed the mechanism underlying the antisecretory gastric acid effect of Plectranthus barbatus Andrews (Lamiaceae) and active constituents. Popularly known as "false-boldo", this plant is used in Brazilian folk medicine to treat gastrointestinal and hepatic ailments. The plant aqueous extract (AE) and isolated compounds were assayed in vivo in pylorus-ligated mice, and in vitro on acid secretion measured as [(14)C]-aminopyrine ([(14)C]-AP) accumulation in rabbit gastric glands and gastric H(+),K(+)-ATPase preparations. Injected into the duodenal lumen, the AE of the plant leaves (0.5 and 1.0 g/kg) decreased the volume (62 and 76%) and total acidity (23 and 50%) of gastric acid secretion in pylorus-ligated mice. Bioguided purification of the AE yielded an active fraction (IC(50)=24 microg/ml) that inhibited acid secretion in rabbit gastric glands with a potency 10 to 18 times greater than that of the originating extract, on both the basal and stimulated acid secretion by histamine (His) (1 microM) or bethanechol (100 microM). At the same concentrations the gastric H(+),K(+)-ATPase activity was also inhibited. The active constituent was chemically identified as the abietanoid dienedione plectrinone A which reduced the H(+),K(+)-ATPase activity with IC(50)=171 microM. The results indicate that inhibition of the gastric proton pump by this diterpenoid may account for the antisecretory acid effect and reputed anti ulcer activity of Plectranthus barbatus.

Tea, obesity, and diabetes

Tea has been found to possess widespread biological functions based on a variety of laboratory data. The effects of tea on obesity and diabetes have received increasing attention. This paper reviews the evidence for the connections among tea catechins, and obesity and diabetes. Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects. While few epidemiological and clinical studies show the health benefits of EGCG on obesity and diabetes, the mechanisms of its actions are emerging based on the various laboratory data. These mechanisms may be related to certain pathways, such as through the modulations of energy balance, endocrine systems, food intake, lipid and carbohydrate metabolism, the redox status, and activities of different types of cells (i. e., fat, liver, muscle, and beta-pancreatic cells). Because the EGCG receptor, the so-called 67-kDa laminin receptor (LR), has been discovered with colocalization of other types of LR and cytoskeleton in both cancer cells and normal cells, this may explain that EGCG possesses numerous actions. The mechanistic results of this review may possibly be utilized in the treatment of obesity, diabetes, and other related diseases using tea- and EGCG-based folk medicines.

Inhibition of P-glycoprotein function by tea catechins in KB-C2 cells

We studied the effects of tea catechins, (-)-epicatechin (EC), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epigallocatechin gallate (EGCG) on the P-glycoprotein (P-gp) function in multidrug-resistant P-gp over-expressing KB-C2 cells. EC did not have any effects on cellular accumulation of P-gp substrates, rhodamine-123 and daunorubicin, but the other catechins increased the accumulation in the order of EGC < ECG < EGCG. The effects of EGCG were larger than those of verapamil and quercetin. Since these catechins inhibited the efflux of P-gp substrates, the elevation of substrate accumulation seemed to be induced by the inhibition of the efflux transporter. The results showed that the inhibitory effects of the catechins did not depend on their total hydrophobicity, but significantly depended on their chemical structure. The presence of the galloyl moiety on the C-ring markedly increased the n-octanol/PBS partition coefficients of the catechins and their activity on P-gp. On the other hand, the presence of the trihydric pyrogallol group as the B-ring decreased the partition coefficients but increased the activity on P-gp, compared with the action of the corresponding catechins with a dihydric catechol B-ring.

Antioxidant flavan-3-ols and flavonol glycosides from Maytenus aquifolium

TLC autographic assay revealed, in the EtOAc extract obtained from leaves and root bark of Maytenus aquifolium (Celastraceae), the presence of fi ve compounds exhibiting antioxidant properties towards beta-carotene. They were isolated and identified as epigallocatechin (1), (+) ouratea-catechin (2), proanthocyanidin (3), kaempferol 3-O-alpha-L-rhamnopyranosyl (1-->6)-O-[beta-D-glucopyranosyl (1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-O-beta-D-glucopyranosyl (4) and quercetin 3-O-alpha-L-rhamnopyranosyl (1-->6)-O-[beta-D-glucopyranosyl (1-->3)-O-alpha-L-rhamnopyranosyl-(1-->2)]-O-beta-D-glucopyranosyl (5). The isolates were investigated for their redox properties using cyclic voltammetry and for their radical scavenging abilities through spectrophotometric assay on the reduction of 2,2-diphenyl-pycryl hydrazyl (DPPH). These results were correlated to the inhibition of beta-carotene bleaching on TLC autographic assay and to structural features of the flavonoids.

Inhibitory effects of catechins on neutrophil-dependent gastric inflammation

The inhibitory effects of tea against carcinogenesis have been attributed to the biological activity of the polyphenol fraction of tea. However, the molecular mechanisms of these effects are not completely understood. Chronic inflammation induced by Helicobacterpylori has been proposed to be a causative pathway in the carcinogenesis of stomach cancer. Therefore, an agent possessing anti-inflammatory properties may be chemopreventative against stomach cancer. In the present study, we have investigated the anti-inflammatory effects of tea catechins. After addition of IL-1beta to MKN45 cells, a gastric cancer cell line, or human umbilical vein endothelial cells (HUVECs), IL-8 production was detected in supernatants. This IL-8 production was inhibited by catechins. Incubation of HUVECs or polymorphonuclear leukocytes (PMNs) with IL-1beta or IL-8, respectively, resulted in an increased surface expression of adhesion molecules. Catechins also inhibited this expression of adhesion molecules on HUVECs and PMNs. Of these major effects, the strongest effect of catechins was to reduce expression of the adhesion molecules CD1lb and CD18 on PMNs. These results suggest that tea may inhibit carcinogenesis partly through the anti-inflammatory effects of tea catechins on PMN-dependent gastric mucosal inflammation.

The effect of epigallocatechin gallate on intestinal motility in mice

OBJECTIVES

The epigallocatechin-3-gallate (EGCg) that is present in human diet originates mainly from tea leaves. Catechins have a number of possible application as medicines, however, there is no consistent evidence showing their influence on the gastrointestinal tract. Thus, the aim of the present study was to investigate the effect of EGCg on the motility of the murine isolated intestine.

METHODS

Segments of jejunum submerged in Krebs buffer were exposed to EGCg and the response was recorded under isometric conditions.

RESULTS

EGCg induced a dose-dependent inhibition of spontaneous activity in the jejunum. EGCg induced a decrease in the amplitude and frequency of jejunal contractions. moreover, the rythmicity of spontaneous, activity was altered in the presence of EGCg. A significant effect of EGCg was observed in the presence of 10(-4) M. The effect of EGCg was in part inhibited by pretreatment with methylene blue (guanylate cyclase inhibitor), while tetrodotoxin, (sodium channel blocker), L-nitro arginine methyl ester (nitric oxide synthase inhibitor), and N-ethylmaleimide (adenylate cyclase inhibitor) showed no effect.

CONCLUSIONS

The results of the present study suggest that EGCg inhibits the motility of the jejunum by direct action on smooth muscle cells where a guanylate cyclase-dependent mechanism may be partly involved.

Catechins from green tea (Camellia sinensis) inhibit bovine and human cartilage proteoglycan and type II collagen degradation in vitro

Polyphenolic compounds from green tea have been shown to reduce inflammation in a murine model of inflammatory arthritis, but no studies have been undertaken to investigate whether these compounds are protective to joint tissues. We therefore investigated the effects of catechins found in green tea on cartilage extracellular matrix components using in vitro model systems. Bovine nasal and metacarpophalangeal cartilage as well as human nondiseased, osteoarthritic and rheumatoid cartilage were cultured with and without reagents known to accelerate cartilage matrix breakdown. Individual catechins were added to the cultures and the amount of released proteoglycan and type II collagen was measured by metachromatic assay and inhibition ELISA, respectively. Possible nonspecific or toxic effects of the catechins were assessed by lactate output and proteoglycan synthesis. Catechins, particularly those containing a gallate ester, were effective at micromolar concentrations at inhibiting proteoglycan and type II collagen breakdown. No toxic effects of the catechins were evident. We conclude that some green tea catechins are chondroprotective and that consumption of green tea may be prophylactic for arthritis and may benefit the arthritis patient by reducing inflammation and slowing cartilage breakdown. Further studies will be required to determine whether these compounds access the joint space in sufficient concentration and in a form capable of providing efficacy in vivo.

Pentagalloylglucose, an antisecretory component of Paeoniae radix, inhibits gastric H+, K(+)-ATPase

We purified a compound with strong inhibitory effect on H+, K(+)-ATPase from Paeoniae radix, which has been used in Japan for the treatment of gastritis and peptic ulcers. The compound was identified as 1,2,3,4,6,-penta-o-galloyl-beta-D-glucose by proton nuclear magnetic resonance, carbon-13 nuclear magnetic resonance, and fast atomic bombardment mass spectrometry. The IC50 of the compound for H+, K(+)-ATPase was 166 nmol/l. Kinetic analyses indicated that the inhibition of the enzyme by pentagalloylglucose was noncompetitive with respect to K+. Pentagalloylglucose had relatively weak inhibitory effects for Mg(+)-ATPase (IC50: > 10 mumol/l) and Na+, K(+)-ATPase (IC50: 2.7 mumol/l). Pentagalloylglucose also inhibited the accumulation of [14C]aminopyrine in parietal cells that had been isolated from guinea pig stomach and stimulated by 10 mumol/l histamine (IC50: 7.8 mumol/l) and 1 mmol/l dbc-AMP (IC50: 10 mumol/l). These results suggest that pentagalloylglucose is a potent inhibitor of H+, K(+)-ATPase and may be responsible for inhibition of acid secretion by Paeoniae radix.

Inhibition of gastric H+, K(+)-ATPase by flavonoids: a structure-activity study

Gastric H+, K(+)-ATPase plays a pivotal role in the final step of gastric acid secretion. Over 80 flavonoids, including flavones, flavanones, isoflavones and anthocyanidins were examined for their in vitro effect on gastric H+, K(+)-ATPase and some were found to be inhibitors of this enzyme. Kinetic studies showed that the inhibition of H+, K(+)-ATPase by flavonoids was competitive with respect to ATP, and non-competitive with respect to K+. Structure-activity analysis revealed the following: (1) The inhibitory potency of flavonoids depends on the number of hydroxyl groups up to four per molecule and that above this, no marked enhancement is seen; (2) The hydroxylation pattern is an important determinant of inhibitory potency. Two adjacent hydroxyl groups (catechol-type), three adjacent hydroxyl groups (pyrogallol-type) or hydroxyl groups at C-3, C-5 and C-7 are a minimum requirement for high potency inhibition; (3) Protection of the hydroxyl group(s) by glycosylation or methylation decreases potency; (4) Saturation of the C-2-C-3 double bond results in a decrease in potency; and (5) A ketone at C-4 is not essential for inhibition.

In vitro and in vivo activities of tea catechins against Helicobacter pylori

The catechin epigallocatechin gallate showed the strongest activity of the six tea catechins tested against Helicobacter pylori (MIC for 50% of the strains tested, 8 microg/ml). It had bactericidal activity at pH 7 but not at pH </=5.0. In infected Mongolian gerbils, H. pylori was eradicated in 10 to 36% of the catechin-treated animals, with significant decreases in mucosal hemorrhage and erosion. Tea catechins, therefore, may have therapeutic effects on H. pylori infection.

In vitro and in vivo activities of tea catechins against Helicobacter pylori

The catechin epigallocatechin gallate showed the strongest activity of the six tea catechins tested against Helicobacter pylori (MIC for 50% of the strains tested, 8 microg/ml). It had bactericidal activity at pH 7 but not at pH </=5.0. In infected Mongolian gerbils, H. pylori was eradicated in 10 to 36% of the catechin-treated animals, with significant decreases in mucosal hemorrhage and erosion. Tea catechins, therefore, may have therapeutic effects on H. pylori infection.