Gastric anti-ulcer activity of (+)-cyanidanol-3, a histidine decarboxylase inhibitor

Antioxidant and Antiulcerogenic Activity of the Dry Extract of Pods of Libidibia ferrea Mart. ex Tul. (Fabaceae)

Ethnomedicinal studies in the Amazon community and in the Northeast region of Brazil highlight the use of Libidibia ferrea fruits for the treatment of gastric problems. However, there are no data in the literature of this pharmacological activity. Thus, the aim of this paper is to provide a scientific basis for the use of the dry extract of L. ferrea pods (DELfp) for the treatment of peptic ulcers. Phytochemical characterization was performed by HPLC/MS. In vitro antioxidant activity was assessed using DPPH, ABTS, phosphomolybdenum, and superoxide radical scavenging activity. The gastroprotective activity, the ability to stimulate mucus production, the antisecretory activity, and the influence of -SH and NO compounds on the antiulcerogenic activity of DELfp were evaluated. The healing activity was determined by the acetic acid-induced chronic ulcer model. Anti-Helicobacter pylori activity was investigated. HPLC/MS results identified the presence of phenolic compounds, gallic acid and ellagic acid, in DELfp. The extract showed antioxidant activity in vitro. In ulcers induced by absolute ethanol and acidified ethanol, the ED₅₀ values of DELfp were 113 and 185.7 mg/kg, respectively. DELfp (100, 200, and 400 mg/kg) inhibited indomethacin-induced lesions by 66.7, 69.6, and 65.8%, respectively. DELfp (200 mg/kg) reduced gastric secretion and H⁺ concentration in the gastric contents and showed to be independent of nitric oxide (NO) and dependent on sulfhydryl (-SH) compounds in the protection of the gastric mucosa. In the chronic ulcer model, DELfp reduced the area of the gastric lesion. DELfp also showed anti-H. pylori activity. In conclusion, DELfp showed antioxidant, gastroprotective, healing, and antiulcerogenic activities. The mechanism of these actions seems to be mediated by different pathways and involves the reduction of gastric secretion and H⁺ concentration, dependence on sulfhydryl compounds, and anti-H. pylori activity. All these actions support the medicinal use of this species in the management of peptic ulcers.

Effect of Byrsonima sericea DC. leaf extracts on mice gastrointestinal tract

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Byrsonima sericea DC. (Malpighiaceae) was studied for phenolic contents.

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Byrsonima sericea (BSEE) ethanolic extracts explored Indomethacin induced gastric lesion.

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BSEE lowers rates of AST, ALT, animal weight and relative organ weight.

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Anti-diarrheal and antioxidant activity from leaf extracts were observed in the current investigation.

Byrsonima sericea DC. (Malpighiaceae) leaves are popularly folk medicine in Brazil used to treat gastro-intestinal disorders including diarrhea and gastric diseases. Ethanol extract (BSEE), ethyl acetate extract (BSEAE) and hexane extract (BSHE) of the leaf part of Byrsonima sericea DC were characterized for their total phenolics, proanthocyanidins and flavonoids content. The total antioxidant capacity of extracts was determined. The ethnopharmacological use of B. sericea leaves was evaluated by assaying BSEE for gastroprotective activity in stomach ulcer induced by indomethacin, intestinal motility and toxicity. Abundance of phenols mainly tannins was found in BSEE. Total phenolics, flavonoids and proanthocyanidins content in BSEE were found to be 0.371, 0.172 and 1.3 × 10-4 (mg/g) respectively. BSEE showed concentration dependent significant scavenging of DPPH values 90.0 (%) respectively. Moreover, oral doses of 500 and 1000 mg/kg did not cause mortality, and there was no difference in animals weight, organs relative weight and alanine transaminase (ALT) and aspartate transaminase (AST), as compared to the control group. Doses of 250, 500 and 1000 mg/kg inhibited the gastric lesions induced by indomethacin in 52, 60 and 62 % respectively. The dose of 1000 mg/kg decreased intestinal motility in animals. The presence of phenolic compounds, including tannins could be associated with the anti-diarrheal action and the antioxidant properties could collaborate to the gastroprotective and anti- diarrheal activities, confirming its popular use of the plant.

Potential Antiulcer Agents From Plants: A Comprehensive Review

Background:

Peptic ulcer is a deep gastrointestinal erosion disorder that involves the entire mucosal thickness and can even penetrate the muscular mucosa. Nowadays, several plants and compounds derived from it have been screened for their antiulcer activity. In the last few years, there has been an exponential growth in the field of herbal medicine. This field has gained popularity in both developing and developed countries because of their natural origin and less side effects.

Objective:

This review aims to provide a comprehensive summary of currently available knowledge of medicinal plants and phytoconstituents reported for their anti-ulcer properties.

Methods:

The worldwide accepted database like SCOPUS, PUBMED, SCIELO, NISCAIR, ScienceDirect, Springerlink, Web of Science, Wiley, SciFinder and Google Scholar were used to retrieve available published literature.

Results:

A comprehensive review of the present paper is an attempt to list the plants with antiulcer activity. The review narrates the dire need to explore potential chemical moieties that exert an antiulcer effect, from unexploited traditional plants. Furthermore, the present study reveals the intense requirement to exploit the exact mechanism through which either the plant extracts or their active constituents exhibit their antiulcer properties.

Conclusion:

This article is the compilation of the plants and its constituents reported for the treatment of peptic ulcers. The Comprehensive data will surely attract the number of investigators to initiate further research that might lead to the drugs for the treatment of ulcers. As sufficient scientific data is not available on plants, most of the herbals cannot be recommended for the treatment of diseases. This can be achieved by research on pure chemical structures derived from plants or to prepare new lead compounds with proven beneficial preclinical in vitro and in vivo effects. However, a lot remains to be done in further investigations for the better status of medicinal plants.

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.

Calamintha nepeta (L.) Savi and its Main Essential Oil Constituent Pulegone: Biological Activities and Chemistry

Medicinal plants play an important role in the treatment of a wide range of diseases, even if their chemical constituents are not always completely recognized. Observations on their use and efficacy significantly contribute to the disclosure of their therapeutic properties. Calamintha nepeta (L.) Savi is an aromatic herb with a mint-oregano flavor, used in the Mediterranean areas as a traditional medicine. It has an extensive range of biological activities, including antimicrobial, antioxidant and anti-inflammatory, as well as anti-ulcer and insecticidal properties. This study aims to review the scientific findings and research reported to date on Calamintha nepeta (L.) Savi that prove many of the remarkable various biological actions, effects and some uses of this species as a source of bioactive natural compounds. On the other hand, pulegone, the major chemical constituent of Calamintha nepeta (L.) Savi essential oil, has been reported to exhibit numerous bioactivities in cells and animals. Thus, this integrated overview also surveys and interprets the present knowledge of chemistry and analysis of this oxygenated monoterpene, as well as its beneficial bioactivities. Areas for future research are suggested.

Gastric anti-ulcer activity of silymarin, a lipoxygenase inhibitor, in rats

Oral treatment with silymarin was found to be effective in the prevention of gastric ulceration induced by cold-restraint stress, in rats. Statistically significant ulcer index values with respect to the control group, were observed. In 6 h pyloric-ligated animals silymarin showed a significant reduction in the number and severity of the ulcers; however, it did not alter the gastric secretion volume or acidity although histamine concentration was significantly decreased. In absolute ethanol-induced ulcers, treatment with silymarin 1 or 2 h before the anti-ulcerogenic agent, did not prevent the formation of gastric lesions. Furthermore, the hexosamine content was decreased significantly, but the total protein output was enhanced, showing similar values to those with the standard drug, carbenoxolone. These results suggest that the anti-ulcerogenic effect of silymarin could be related to its inhibitory mechanism of enzymatic peroxidation by the lipoxygenase pathway, avoiding leukotriene synthesis.

Flavonoids with gastroprotective activity

Peptic ulcers are a common disorder of the entire gastrointestinal tract that occurs mainly in the stomach and the proximal duodenum. This disease is multifactorial and its treatment faces great difficulties due to the limited effectiveness and severe side effects of the currently available drugs. The use of natural products for the prevention and treatment of different pathologies is continuously expanding throughout the world. This is particularly true with regards to flavonoids, which represent a highly diverse class of secondary metabolites with potentially beneficial human health effects that is widely distributed in the plant kingdom and currently consumed in large amounts in the diet. They display several pharmacological properties in the gastroprotective area, acting as anti-secretory, cytoprotective and antioxidant agents. Besides their action as gastroprotectives, flavonoids also act in healing of gastric ulcers and additionally these polyphenolic compounds can be new alternatives for suppression or modulation of peptic ulcers associated with H. pylori. In this review, we have summarized the literature on ninety-five flavonoids with varying degrees of antiulcerogenic activity, confirming that flavonoids have a therapeutic potential for the more effective treatment of peptic ulcers.

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.

Antiulcerogenic effects of Tylophora conspicua in male rats

Studies were undertaken on the effect of a crude (TC) and an alkaloid fraction (TA) of the leaf extracts of Tylophora conspicua on indomethacin-induced gastric ulceration and gastric acid secretion in male albino rats. Both the TC and TA produced a dose-dependent inhibition of gastric ulceration. At a dose level of 40 mg/kg TC and TA were more effective (TA being more potent) than propranolol in inhibiting gastric ulceration. The highest dose of the extracts used (80 mg/kg) completely inhibited gastric ulceration. Intravenous administration of the TC and TA significantly decreased acid output at low dose (20 mg/kg), medium dose (40 mg/kg) and high dose (80 mg/kg) from the peak basal of 0.54 +/- 0.02 mEq/L/min to 0. 49 +/- 0.02 mEq/L/min, 0.35 +/- 0.01 mEq/L/min and 0.21 +/- 0.02 Meq/L/min respectively. 80 mg/kg of TC and TA significantly reduced the histamine (1 mg/kg) induced gastric acid secretion. The results suggest that the antiulcer activity of Tylophora conspicua might be produced by gastric acid inhibition.

Effects of aqueous extracts from Quercus ilex L. root bark, Punica granatum L. fruit peel and Artemisia herba-alba Asso leaves on ethanol-induced gastric damage in rats

The gastroprotective effect of tannic acid and the aqueous extract of Quercus ilex L. root bark, Punica granatum L. fruit peel and Artemisia herba-alba Asso leaves was investigated in the rat against ethanol-induced damage. Tannic acid, Q. ilex and P. granatum extracts gave 100% precipitation of ovine haemoglobin in vitro, whereas A. herba-alba extract was devoid of any protein-binding property. Oral administration of these plant extracts or tannic acid induced a significant decrease in gastric lesions (47.7%-76%). The observed protection was more pronounced when the test solution was given at the same time with ethanol, except for Q. ilex extract. The acid content of the stomach was significantly increased by P. granatum (368%) and A. herba-alba (251%) extracts prepared in ethanol. It is suggested that monomeric and polymeric polyphenols can strengthen the gastric mucosal barrier.

Oral anti-inflammatory and anti-ulcerogenic activities of a hydroalcoholic extract and partitioned fractions of Turnera ulmifolia (Turneraceae)

Anti-inflammatory studies were conducted on rats or mice using a crude hydroalcoholic extract of the aerial parts of Turnera ulmifolia and it's partitioned fractions, i.e. the aqueous, ethyl acetate and ethanolic fractions. The hydroalcoholic extract and it's fractions (aqueous and ethanolic) inhibited carrageenan-induced edema. However, only the ethanolic fraction was used in the other experiments due to it's yield. The extract also inhibited the cotton pellet granuloma and the increase of vascular permeability induced by histamine, 5-hydroxytryptamine and prostaglandin E2, but not that produced by bradykinin. The extract or the fraction did not present analgesic activity in the writhing test using acetic acid and did not reduce croton oil-induced ear edema in mice. When the ethanolic fraction and LPS were administered i.p. to Balb/C mice 72 h before blood or peritoneal fluid collection, no changes were observed in the white or total blood cell counts in the peripheral blood. On the other hand, changes were observed in both total and differential cell counts in the peritoneal exudate since all doses of the fraction reduced the number of total leukocytes (mainly lymphocytes) obtained from the peritoneal exudate. In contrast to nonsteroidal anti-inflammatory drugs, the administration of the hydroalcoholic extract or the ethanolic fraction alone did not potentiate gastric mucosal lesions induced by aspirin. The extract and the fraction inhibited the appearance of gastric lesions induced by indomethacin, ethanol and pylorus ligature, but not those induced by stress. As also observed with carbenoxolone, the ethanolic fraction increased the wall mucus in hypothermical-restraint stress-induced gastric lesions. The anti-ulcerogenic effect of the extract and of the ethanolic fraction may be related to an increase of mucosal defensive factors, such as prostaglandin and mucus. The anti-inflammatory actions of the extract and the fraction may be due to an inhibitory effect on histamine and cyclooxygenase II, but not on cyclooxygenase I, because the extract and it's fraction present both anti-inflammatory and anti-ulcerogenic effects. The major substances present in the ethanolic fraction are flavonoids which will be isolated and identified.

Effects of cisapride on ulcer formation and gastric secretion in rats: comparison with ranitidine and omeprazol

1. The antiulcerogenic effects of cisapride, a potent benzamide-stimulating gastrointestinal motility agent, were studied on cold-resistant and pylorus-ligated gastric ulcers. Acidity, composition of gastric secretion, and quantitative and qualitative changes on mucus glycoprotein content were also determined. These effects were compared with those of ranitidine (50 mg/kg) and omeprazol (10 mg/kg). 2. Oral cisapride (10-100 mg/kg) dose-relatedly and significantly (P < 0.01, P < 0.05) decreased the severity of the lesions induced by cold-resistant stress. In stressed rats, cisapride increased the amount of mucus secretion and markedly enhanced the glycoprotein content. Morphometric evaluation of mucus secretion revealed a significant increase in both the PAS area (neutral glycoproteins) and Alcian blue area (sulfated glycoproteins). 3. In 4 h pyloric-ligated animals, cisapride (10-100 mg/kg) showed a significant reduction in the number and severity of ulcers (P < 0.01) and histamine concentration (P < 0.01, P < 0.001). In addition, at the highest doses (50-100 mg/kg), cisapride produced a significant decreases in acidity; however, it did not alter the gastric volume secretion or pepsin concentrations. 4. These results suggest that cisapride shows antiulcerogenic effects which could possibly be explained through antisecretory and cytoprotective mechanisms involving an enhancement of cuality and production of gastric mucus.

Ebselen, a seleno-organic compound, protects against ethanol-induced murine gastric mucosal injury in both in vivo and in vitro systems

The inhibitory effect of the seleno-organic compound ebselen on ethanol-induced murine gastric mucosal injury was examined. In an in vivo study, absolute ethanol (50 microliters/mouse, oral) produced marked gastric mucosal necrosis along with hemorrhage or edema and elevations in both lipid peroxide and peptidoleukotriene levels in the fundic mucosa. Pretreatment with ebselen (30 and 100 mg/kg, oral) significantly prevented this gastric mucosal injury and, further, remarkably decreased the elevated lipid peroxide and peptidoleukotriene levels. In an in vitro study using a murine gastric surface mucous cell line GSM06, exposure to ethanol concentration dependently elicited cell damage (7.5-17.5% ethanol) and an increase in lipid peroxides without alterations in peptidoleukotrienes (15% ethanol). Addition of ebselen (10 and 100 microM) to this system (15% ethanol) significantly inhibited the cell damage and completely prevented the increase in lipid peroxide level. These results indicate that ebselen protects against murine gastric mucosal injury both in vivo and in vitro, and that this protection may be related at least in part to its inhibitory action on lipid peroxides.

Prevention by rutin of gastric lesions induced by ethanol in rats: role of endogenous prostaglandins

1. This study was designed to demonstrate the cytoprotective effect of Rutin against ethanol-induced gastric injury in rats and to determine whether this cytoprotective effect is mediated by endogenous prostaglandins. 100 and 200 mg/kg of Rutin given orally 1 hr before administration of 1 ml of 100% ethanol significantly (p < 0.01) reduced the area of macroscopic lesions induced by ethanol (84.16 +/- 23.01 and 54.75 +/- 16.05 respectively) when compared to distilled water (305.60 +/- 67.20). However, it did not induce changes in the amount and total proteins and hexosamines content of gastric mucus. 2. Pretreatment with indomethacin, 10 mg/kg s.c. 30 min before Rutin administration, slightly but not significantly reduced the cytoprotective effect. 3. The levels of PGE2 present in the mucous material were not significantly modified with administration of Rutin (100 mg/kg). 4. These results show that Rutin has a cytoprotective effect against ethanol injury in the rat, but this property does not appear to be mediated by endogenous prostaglandins.

Ulcer-protecting effects of naringenin on gastric lesions induced by ethanol in rat: role of endogenous prostaglandins

This study was designed to determine the cytoprotective properties of naringenin and the involvement of endogenous prostaglandins on mucosal injury produced by absolute ethanol. Gastric glands were also histologically analysed. Oral pretreatment with the highest dose of naringenin (200 mg kg-1), 240 min before absolute ethanol, was the most effective in ulcer prevention. Subcutaneous administration of indomethacin (10 mg kg-1) to the animals treated with naringenin (200 mg kg-1) partially inhibited the gastric protection but there was no increase in prostaglandin E2. All treated groups showed a marked increase in gastric mucus, although this increase was less in animals pretreated with indomethacin. Total proteins and hexosamine content decreased in the groups receiving indomethacin. Histomorphometric evaluation of the gastric damage, with the highest dose of naringenin (200 mg kg-1), confirmed a significant increase of mucus production accompanied by a parallel reduction of gastric lesion.

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

Five catechins, (+)-catechin, (-)-epicatechin, (-)-epicatechin gallate, (-)-epigallocatechin and (-)-epigallocatechin gallate, inhibited gastric H+, K(+)-ATPase activity with IC50 values ranging from 1.7 x 10(-4) to 6.9 x 10(-8) M, with (-)-epigallocatechin gallate as the most potent inhibitor. The intensity of inhibitor activity paralleled the number of phenolic hydroxy groups in the molecule. The inhibition of the enzyme by (-)-epicatechin was competitive with respect to ATP and noncompetitive with respect to K+. These findings suggest that the anti-secretory and anti-ulcerogenic effects of catechins previously reported, are due to their inhibitory activity on gastric H+, K(+)-ATPase.

Stimulatory actions of bioflavonoids on tyrosine uptake into cultured bovine adrenal chromaffin cells

The effects of flavonoids on L-[14C]tyrosine uptake into cultured adrenal chromaffin cells were examined. Flavone markedly stimulated tyrosine uptake into these cells in a manner dependent on its concentration. Apigenin also caused a moderate stimulatory action, but quercetin had no significant effect on the uptake. Flavone also stimulated the uptake of histidine, but did not affect the uptake of serine, lysine, or glutamic acid. These results are considered to propose the possibility that flavonoids may be able to stimulate the precursor uptake into the cells, resulting in an enhancement of the biogenic amine production.

Flavonoids as inhibitors of rat liver monooxygenase activities

Flavanone and six hydroxylated derivatives, and cianidanol and eight ethers and esters thereof, were investigated as inhibitors of cytochrome P-450 mediated reactions in rat liver microsomes. The IC50 values towards aminopyrine N-demethylation varied over a 20-fold range and were shown to depend on the pattern of hydroxylation (flavanone derivatives) and on lipophilicity (cianidanol derivatives). In the latter case, a bilinear relationship exists, the optimal log P being 2.92. Using selected compounds, IC50, Km and Vmax values were determined for aminopyrine N-demethylation, biphenyl 4-hydroxylation, and biphenyl 2-hydroxylation. Depending on the inhibitor and on the activity examined, non-competitive, competitive, or mixed inhibition was seen. Interaction with cytochrome P-450 was also studied spectrally and was always found to result in a modified type II difference spectrum (ligand binding). A dual binding mode is postulated, involving electrostatic and lipophilic interactions.

A possible mechanism of protection by polyamines against gastric damage induced by acidified ethanol in rats: polyamine protection may depend on its antiperoxidative properties

The protective mechanism of polyamines against acidified ethanol-induced gastric damage was studied. Their oral administration prevented the formation of gastric mucosal lesions induced by 90% ethanol in 150 mM HCl in a dose-dependent manner, with the order of the protective potency being spermine greater than spermidine greater than putrescine. The acidified ethanol-induced lesions were accompanied by a concomitant increase in gastric mucosal lipid peroxide levels, but spermine in a protective dose could prevent the increment of lipid peroxides. Polyamines, in a concentration-dependent fashion, inhibited the reduction of nitroblue tetrazolium by superoxide anion radicals generated in vitro in the xanthine-xanthine oxidase system and the lipid peroxidation in vitro induced by ferrous ion in the porcine gastric mucosal homogenate. The order of the superoxide scavenging potency and the inhibitory potency of iron-induced lipid peroxidation by polyamines corresponded to the order to the protective potency against acidified ethanol-induced gastric lesions. The present results suggest that cytoprotection by polyamines may be responsible for their antiperoxidative activities.

Gastric protection by meciadanol. A new synthetic flavonoid inhibiting histidine decarboxylase

Flavonoids reportedly inhibit histidine decarboxylase and reduce gastric mucosal histamine content. We studied the effects of acute and chronic intragastric administration to rats of meciadanol, a new synthetic flavonoid (Zyma S.A., Nyon, Switzerland). The action of meciadanol was compared to that of 16,16-dimethyl PGE2. Meciadanol did not affect acid or pepsin output at any dose used. High doses of 16,16-dimethyl PGE2 reduced both acid and pepsin output. Meciadanol partially prevented aspirin-induced lesions but the prevention required chronic administration of meciadanol. In contrast, a single dose of meciadanol completely prevented ethanol-induced lesions. Chronic administration of meciadanol also completely prevented ethanol-induced lesions. 16,16-Dimethyl PGE2 prevented both aspirin-induced and ethanol-induced lesions in doses that did not affect acid or pepsin output. Meciadanol did not influence the effect that either aspirin or ethanol had on endogenous mucosal PGI2. Thus, the dose range of meciadanol that protected against ulcerogens did not affect either gastric acid secretion or pepsin output. Therefore, we conclude that meciadanol's action represents true cytoprotection, which was previously attributed only to prostaglandins.

Antiulcer and gastroprotective effects of solon, a synthetic flavonoid derivative of sophoradin. Role of endogenous prostaglandins

Solon is a synthetic isoprenyl flavonoid derived from sophoradin which is isolated from the root of an ancient Chinese plant. Solon was administered orally or intraperitoneally to rats. It inhibited dose dependently gastric ulcers produced by acidified aspirin, water immersion and restraint stress. Solon was also gastroprotective for the stomach as it reduced dose dependently the gastric necrotic lesions induced by absolute ethanol given orally. The degree of gastroprotection decreased with time, the optimal effects occurring 60-90 min after oral administration. Pretreatment with indomethacin partly prevented the gastroprotective effects of Solon. When given alone to fasted rats, Solon increased dose dependently the mucosal content of prostaglandins (PG), suggesting that the protective effects of this drug may be mediated at least in part by endogenous PG.

Histidine decarboxylase inhibition: a novel approach towards the development of an effective and safe gastric anti-ulcer drug

The involvement of histamine in mediating gastric function under normal and pathological conditions has been largely established. The relationship between gastric acid production and peptic ulcer diathesis is also well known. Recently, endogenous histamine formation and its release from mast cells has been implicated in the pathogenesis of human and experimental gastric ulcers produced by restraint and pyloric ligation. It has also been implicated in the gastric mucosal damage produced by drugs like aspirin, phenylbutazone and reserpine. These observations suggest that histidine decarboxylase inhibitors may be useful in the prevention of such lesions. Our studies on the evaluation of some histidine decarboxylase inhibitors show that these compounds have a promising potential for developing an effective and safe anti-ulcer drug. This mini-review incorporates the results of our studies which have been adequately supported by other studies as well.

The gastric antisecretory activity of 3-methoxy-5,7,3'4'-tetrahydroxyflavan (ME)--a specific histidine decarboxylase inhibitor in rats

3-Methoxy-5,7,3'4'-tetrahydroxyflavan (ME), a specific histidine decarboxylase inhibitor, has been shown to significantly reduce the gastric acid secretion and gastric tissue histamine levels in 6 h pylorus ligated rats. It has been found to be as effective as cimetidine in reducing the gastric acid secretion. However, cimetidine does not affect the gastric tissues histamine levels in the normal or pylorus ligated rats. These observations clearly establish that the two drugs reduce the gastric acid secretion by different mechanisms and suggest that their combination may show a potentiated gastric anti-ulcer activity.

Immunoenhancing effect of flavonoid compounds on lymphocyte proliferation and immunoglobulin synthesis

Flavonoid compounds are lipophilic agents which can interact with membrane lipids and may affect responsiveness of immune cells. We therefore studied whether cianidanol ((+)-catechin), the O-methyl-derivative (+)-3-methoxy-5,7,3',4'-tetrahydroxyflavan and palmitoyl-derivative (+)-3-palmitoyl-5,7,3',4'-tetrahydroxyflavan influence T and B cell functions. In addition, immunomodulatory property of ubiquinone 50 was also investigated. As controls were used cyclosporin A and inosine which are known to inhibit or enhance immune responses, respectively. The in vitro spontaneous, antigen and mitogen induced proliferation as well as immunoglobulin synthesis of peripheral blood mononuclear cells from healthy individuals was determined in the presence of different concentrations of the agents. All flavonoid compounds and ubiquinone 50 significantly increased (p less than 0.05 - less than 0.01) the spontaneous lymphocyte transformation but hardly affected antigen, alloantigen and mitogen induced proliferative response. Only cianidanol and O-methyl-derivative enhanced significantly (p less than 0.05 - less than 0.01) spontaneous, pokeweedmitogen and Staphylococcus aureus Cowan I induced immunoglobulin synthesis while the palmitoyl-derivative and ubiquinone 50 had only minor influence on B cell function. In contrast, Staphylococcus aureus induced immunoglobulin production was neither increased by inosine nor suppressed by cyclosporin A. These studies show that especially cianidanol and the O-methyl-derivative can exert an immunoenhancing effect on T and B cell functions.

Histamine receptor blockade (H2) versus inhibition of histamine synthesis in stress ulceration in rats

Cold and restraint stress in rats induced gastric mucosa lesions, increased gastric mucosa histidine decarboxylase activity and elevated hypothalamic content. Cimetidine did not modify the biochemical effects induced by stress but partially protected against gastric ulceration. alpha-Fluoromethyl histidine inhibited the increase of histidine decarboxylase activity in the gastric mucosa, inhibited the rise of hypothalamic histamine content and decreased the incidence of gastric lesions to the same extent as did cimetidine.

Histidine decarboxylase inhibition by O-methyl-3(+)catechin and gastric acid secretion in the cat

In the conscious cat the histidine decarboxylase inhibitor O-methyl-3(+)catechin (Zy 15029) promoted a dose-dependent atropine-sensitive increase in basal acid output. Gastric acid secretion stimulated by food or insulin at different time intervals after pretreatment with Zy 15029 was dose and time dependently diminished up to 70% whereas acid output following pentagastrin stimulation was not reduced by doses effective against the former two stimuli. Only a high dose, which due to side effects has to be claimed as not tolerable in the cat, reduced acid output by about 40%, when application of Zy 15029 and stimulation were 90 min apart. It is suggested that in the cat gastric acid response following the three different stimuli was at least in part but to a variable extent mediated by endogenous histamine. Dose-dependent side effects of Zy 15029 might have been due to histidine decarboxylase inhibition in brain and changes in histaminergic neurotransmission.