Comparison of the gastroprotective effect of a diterpene lactone isolated from Croton cajucara with its synthetic derivatives

Quantification of Barbatusin and 3β-Hydroxy-3-deoxybarbatusin in Plectranthus Species by HPLC-DAD

The concentration of diterpenes barbatusin (1) and 3β-hydroxy-3-deoxybarbatusin (2) in the extracts from leaves of Plectranthus grandis, P. barbatus, P. ornatus, and P. amboinicus was evaluated by HPLC-DAD analysis on a Luna C-18 column, using isocratic mixtures of water and acetonitrile as eluents. The regression equations were obtained with good linearity (r² > 0.99) and limit of quantifications was higher than 0.1 µg/mL. The precision (lower than 3.5%, within day) and accuracy (higher than 81.7% and lower than 107.6%) of the methods were adequate. Barbatusin (1) was detected in P. grandis (15.432 ± 2.28 mg/g) and P. barbatus (5.198 ± 3.45 mg/g) extracts, while compound 2 was detected in P. grandis (4.068 ± 3.34 mg/g), P. barbatus (0.654 ± 5.86 mg/g), P. amboinicus (0.160 ± 7.25 mg/g), and P. ornatus (0.763 ± 5.10 mg/g). The evaluated validation parameters were satisfactorily achieved, and the developed methodology represents a suitable tool for application in the quantification of barbatusin (1) and 3β-hydroxy-3-deoxybarbatusin (2) in Plectranthus species.

Antiulcer activity and subacute toxicity of trans-dehydrocrotonin from Croton cajucara

The antiulcerogenic activity of trans-dehydrocrotonin (DHC), a nor-clerodane diterpene isolated from Croton cajucara Benth. (Euphorbiaceae), and its subacute (35 days) toxicity were studied in mice and rats, respectively. For the antiulcerogenic tests, models of gastric ulcers induced in mice by ethanol/HCl or stress were used. In both models, an oral dose of DHC (100 mg/kg) significantly reduced (P <0.01) the formation of gastric lesions. DHC was also tested for its ability to scavenge free radicals, but no such action was observed in rat liver mitochondria. To assess the subacute toxicity, rats were treated orally with DHC (25, 50 and 100 mg/kg) for 5 weeks. A significant increase in liver weight was observed in male and female rats at highest doses, whereas a significant reduction in plasma alkaline phosphatase and cholesterol levels and an increase in gamma glutamyl transpeptidase were observed only at the highest dose (100 mg/kg) in female rats. DHC caused histopathological alterations in the liver that included a turbid tumefaction, microvacuolar degeneration and nuclear alterations. Despite the beneficial antiulcerogenic activity of DHC, our results suggest that the long-term use of this compound may induce liver damage.

Gastroprotective activity of ferruginol in mice and rats: effects on gastric secretion, endogenous prostaglandins and non-protein sulfhydryls

The gastroprotective mechanism of the natural diterpene ferruginol was assessed in mice and rats. The involvement of gastric prostaglandins (PGE2), reduced glutathione, nitric oxide or capsaicin receptors was evaluated in mice either treated or untreated with indometacin, N-ethylmaleimide (NEM), N-nitro-L-arginine methyl ester (L-NAME) or ruthenium red, respectively, and then orally treated with ferruginol or vehicle. Gastric lesions were induced by oral administration of ethanol. The effects of ferruginol on the parameters of gastric secretion were assessed in pylorus-ligated rats. Gastric PGE2 content was determined in rats treated with ferruginol and/or indometacin. The reduction of gastric glutathione (GSH) content was determined in rats treated with ethanol after oral administration of ferruginol, lansoprazole or vehicle. Finally, the acute oral toxicity was assessed in mice. Indometacin reversed the gastroprotective effect of ferruginol (25 mg kg−1) but not NEM, ruthenium red or L-NAME. The diterpene (25 mg kg−1) increased the gastric juice volume and its pH value, and reduced the titrable acidity but was devoid of effect on the gastric mucus content. Ferruginol (25, 50 mg kg−1) increased gastric PGE2 content in a dose-dependent manner and prevented the reduction in GSH observed due to ethanol-induced gastric lesions in rats. Single oral doses up to 3 g kg−1 ferruginol did not elicit mortality or acute toxic effects in mice. Our results showed that ferruginol acted as a gastroprotective agent stimulating the gastric PGE2 synthesis, reducing the gastric acid output and improving the antioxidant capacity of the gastric mucosa by maintaining the GSH levels.

Gastroprotective and cytotoxic effect of semisynthetic ferruginol derivatives

The gastroprotective abietane diterpene ferruginol has been shown to present high cytotoxicity. In order to obtain active compounds with less cytotoxicity, 18 semisynthetic ferruginol derivatives and totarol were assessed for their gastroprotective effects in the HCl/ethanol-induced gastric lesion model in mice, as well as for cytotoxicity in human gastric epithelial cells (AGS) and human lung fibroblasts (MRC-5). At 20 mg kg−1, the greatest gastroprotective effects were provided by abieta-8,11,13-triene (1), abieta-8,11,13-trien-12-yl-2-chloropropanoate (8), abieta-8,11,13-trien-12-yl propenoate (9), 12-(2,3,4,6-tetra-O-acetyl-β-D-glucopyranosyloxy)-abieta-8,11,13-triene (17) and 12-(β-D-galactopyranosyloxy)-abieta-8,11,13-triene (18), all of which were as active as the reference drug lansoprazole at 20 mg kg−1, reducing gastric lesions by 69, 76, 67, 72 and 61%, respectively. No relation was observed between lipophilicity and the gastroprotective effect. Compounds that showed the greatest cytotoxicity towards AGS cells were ferruginol (2), the corresponding formate (5), acetate (6), propionate (7), 8, 9, 12-(β-D-glucopyranosyloxy)-abieta-8,11,13-triene (16), 18 and totarol (20) (IC50 18–44 μM). Ferruginol and compounds 5–9, 16, 18 and 20 were the most toxic compounds against fibroblasts (IC50 19–56 μM), with a correlation to AGS cells. The derivative 19 was much more active against AGS cells than towards fibroblasts. The best activity/cytotoxicity ratio was found for compound 17, with a lesion index comparable with lansoprazole at 20 mg kg−1 and cytotoxicity &gt;1000 μM towards MRC-5 and AGS cells, respectively. In conclusion, some derivatives showed a better gastroprotective effect/cytotoxicity ratio than the parent compound ferruginol. A total of 13 new compounds are reported here for the first time.

Gastroprotective activity of a new semi-synthetic solidagenone derivative in mice

The gastroprotective activity of the new semi-synthetic solidagenone derivative 15,16-epoxy-8(9),13(16),14-labdatrien-7β-methoxy-6β-ol (ELMO) has been assessed on the model of HCl/EtOH-induced gastric lesions in mice. Human gastric epithelial cells (AGS) and fibroblasts (MRC-5) were used to determine its mode of action. The effect of ELMO on the prostaglandin E2 content, cellular reduced glutathione (GSH) and protection against damage induced by sodium taurocholate was assessed against AGS cells. The effect of ELMO on the growth of AGS and fibroblast cultures was evaluated. The superoxide anion scavenging capacity of the compound was studied also. The cytotoxicity of ELMO, expressed as cell viability, was assessed using two independent endpoints: neutral red uptake (NRU) and the reduction of 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) for MRC-5 fibroblasts and NRU for AGS cells. A single oral dose of ELMO (10 and 20 mg kg−1) inhibited the appearance of gastric lesions in mice displaying similar values to lansoprazole at 20 mg kg−1. At 40 μm ELMO increased the prostaglandin E2 content but not GSH in AGS cells. The compound showed no effect on sodium taurocholate-induced damage and was devoid of superoxide anion scavenging activity. Concentrations of 0.5, 1, 2 and 4 μm stimulated fibroblast but not AGS cell proliferation. The compound showed weak cytotoxicity with values (IC50) of 411 (NRU) and 418 μm (MTT) for fibroblasts and 261 μm (NRU) for AGS cells. The results support further pharmacological study of this compound as a potential new anti-ulcerogenic drug.

Gastroprotective effect of barbatusin and 3-beta-hydroxy-3-deoxibarbatusin, quinonoid diterpenes isolated from Plectranthus grandis, in ethanol-induced gastric lesions in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Validate the popular use of Plectranthus grandis in gastric disorders through the active components.

AIMS

Isolation of barbatusin (BB) and 3beta-hydroxy-3-deoxibarbatusin (BBOH), diterpenes from Plectranthus grandis, and evaluation of their gastroprotective effect and possible mechanisms of action.

MATERIALS AND METHODS

Isolation and chemical characterization of diterpenes from Plectranthus grandis by chromatographic and spectroscopic methods and evaluation of gastroprotective action of the diterpenes through ethanol-induced gastric injury in mice model. It was evaluated the effect of capsazepine, indomethacin and the role of nitric oxide and K(ATP-) channels on the gastroprotective effect of BBOH and BB. Additionally it was measured the concentrations of gastric mucus, non-proteic-sulfhydryl groups and total thiobarbituric acid-reactive substances.

RESULTS

Orally administered BBOH and BB at doses of 5 and 10mg/kg, markedly reduced the gastric lesions by 59 and 96%, and 32 and 76%, respectively, with superior results as compared to N-acetylcysteine (150 mg/kg, i.p.), reference compound that caused 85% lesion suppression. Although BBOH presented a higher gastroprotection than BB they act by similar mechanisms in relation to N-acetylcysteine, and prevent the depletion of gastric mucus, gastric mucosal non-proteic-sulfhydryl groups as well as the increase in thiobarbituric acid-reactive species. Moreover, the gastroprotective effect of BB was effectively blocked in mice pretreated with TRPV1 antagonist capsazepine, by the non-selective cyclooxygenase inhibitor indomethacin, or by the nitric oxide synthase inhibitor L-NAME but not by K(+)(ATP) channel inhibitor glibenclamide. In contrast, the gastroprotective effect of BBOH was blocked only by indomethacin and glibenclamide pretreatments.

CONCLUSION

The protective role for BBOH and BB affording gastroprotection against gastric damage induced by ethanol indicates that these compounds contribute for the activity of Plectranthus species. The different modes of action are probably related to differences in their chemical structure.

Gastroprotective effect and cytotoxicity of abietane diterpenes from the Chilean Lamiaceae Sphacele chamaedryoides (Balbis) Briq

Objectives

The aim of this report was to isolate, identify and assess the gastroprotective effect and cytotoxicity of abietane diterpenes from the Chilean medicinal plant Sphacele chamaedryoides (Balbis) Briq. (Lamiaceae).

Methods

The isolated compounds were identified by spectroscopic means. The gastroprotective effect of the compounds was studied on the HCl/EtOH-induced gastric lesions model in mice. The cytotoxicity of the compounds was assessed on human normal lung fibroblasts (MRC-5) and gastric adenocarcinoma cells (AGS).

Key findings

From the aerial parts of the plant, five phenolic and five p-quinone abietanes, the sesquiterpene spathulenol and two flavonoids were obtained. The main diterpene from the plant was carnosol (7). Lansoprazole at 20 mg/kg reduced gastric lesions by 64.7% (P &lt; 0.01), being statistically similar to carnosol at doses of 10 and 20 mg/kg; the percent lesion reduction with 7 at 5 mg/kg was 49.3%. At a single oral dose of 5 mg/kg, the diterpenes bearing a p-quinone moiety −6,7-dehydroroyleanone (1), royleanone (2), 7,20-epoxyroyleanone (3), taxoquinone (5) and horminone (6) - presented a gastroprotective effect of 54.4, 70.8, 65.0, 35.8 and 52.7%, respectively. Of the C-7 hydroxy derivatives, the activity was much lower for the 7β-OH isomer. The phenolic diterpenes 7 and 7-oxo-11,12,14-trihydroxy-8,11,13-abietatrien-20-al (8) inhibited gastric lesions by 49.3 and 53.0%, respectively. Royleanone (2), 7,20-epoxyroyleanone (3), horminone (6), 8 and spathulenol proved to be cytotoxic with IC50 values in the range of 11–67 μM. The selective cytotoxicity of compounds 1 (IC50: 61 and 366 μM) and 5 (IC50: 310 and 27 μM) against AGS cells and fibroblasts, respectively, merit additional studies.

Conclusions

All the abietanes obtained from S. chamaedryoides present either one or two phenolic OH groups, a quinone system, or both. Several compounds present in the plant showed higher gastroprotective effect than lansoprazole. The cytotoxic effect of most compounds was found at fairly high concentrations and lacked cell specificity. Further studies are required using different tumour cell lines and viability/proliferation assays to assess the specificity of the isolated compounds. The selective cytotoxicity of compounds 1 and 5 against AGS cells and fibroblasts, respectively, merit additional studies.

Analgesic and Anti-Gastropathic Effects of Salidroside Isolated from Acer tegmentosum Heartwood

The heartwood of Acer tegmentosum(Acereaceae) has been used as a Korean traditional medicinal drug against alcohol poisoning and hepatitis. To find the biologically active substance in A. tegmentosum heartwood, we investigated the protective effects of the heartwood extract and its constituents on pain and gastropathy in mouse. In these experiments, salidroside, a major compound, significantly reduced gastric lesion and pain in mice. Oral administration of salidroside at the 10 and 20 mg/kg doses greatly reduced the gastric lesion induced by HCl/ethanol (inhibitory effect, 51.5 and 68.8%, respectively) and by indomethacin/bethanechol (inhibitory effect, 31.3 and 38.8%, respectively). Salidroside also stabilized pH of gastric juice and the increase of gastric juice secretion and total acid output. Taken together, these results demonstrated that salidroside is the main ingredient of A. tegmentosum heartwood to prevent gastric lesion and pain that can be caused by drinking alcohol.

Bioassay-guided isolation of an anti-ulcer diterpenoid from Croton reflexifolius: role of nitric oxide, prostaglandins and sulfhydryls

Croton reflexifolius H. B. K (Euphorbiaceae) is a very common medicinal plant in the Huastecan region of Mexico that, according to local folk medicine, is considered useful in the treatment of gastritis and gastric ulcer. We have aimed to test the validity of this practice by using the experimental model of an ethanol-induced gastric ulcer in male Wistar rats. The results showed that C. reflexifolius had gastroprotector activity, that the hexane extract had the highest protective activity (64.38+/-7.72%), and that polyalthic acid isolated from this extract was the main active gastroprotector agent. Rats treated orally with polyalthic acid showed a gastroprotective effect similar to that elicited by carbenoxolone. As with carbenoxolone, the effect elicited by polyalthic acid was attenuated by pretreatment with either N(G)-nitro-L-arginine methyl ester (70 mgkg(-1), i.p.), a nitric oxide (NO) synthase inhibitor, or N-ethylmaleimide (10 mgkg(-1), s.c.), a blocker of sulfhydryl groups. This suggested that the gastroprotective mechanism of this diterpenoid involved the participation of both NO and endogenous sulfhydryl groups. Contrary to carbenoxolone, the gastroprotective effect of polyalthic acid was not affected by the inhibition of prostaglandin synthesis with indometacin (10 mgkg(-1), s. c.). In conclusion, Croton reflexifolius contains compounds with gastroprotector activity. Polyalthic acid, which was isolated from this plant, was the main compound with gastroprotector activity, having effectiveness similar to that found with the use of carbenoxolone. Whereas NO and sulfhydryl groups were involved in the mechanisms of gastroprotective action of polyalthic acid, prostaglandins were not.

The antiulcer effect of Croton cajucara Benth in normoproteic and malnourished rats

The aim of the present study is to investigate the antiulcerogenic effects of the essential oil (EO) of Croton cajucara Benth in rats fed with a normal protein (NP) and low-protein diet (MN). NP and MN rats were treated with the essential oil for 15 days after chronic ulceration was induced. The EO accelerated healing of acetic acid-induced gastric lesions in NP and MN rats (p<0.05). In a similar experiment on chronic ulceration, Epidermal Growth Factor (EGF) mRNA expression increased in NP rats but not in MN rats. In assays of acute antiulcerogenic activity, C. cajucara increased somatostatin plasma levels and decreased gastrin plasma levels in both animal groups. The EO significantly prevented ethanol-induced gastric ulcers in NP and MN rats (p<0.001). Histological examination showed initial regeneration, formation of inflammatory infiltrate and angiogenesis in the epithelium surface of acetic acid-induced ulcers in NP and MN rats. C. cajucara prevented gastric lesions in both animal groups when ethanol methodology was used. We concluded that the EO showed an antiulcerogenic activity mediated by increased somatostatin secretion and EGF mRNA expression.

Gastroprotective effect and cytotoxicity of terpenes from the Paraguayan crude drug "yagua rova" (Jatropha isabelli)

A new jatrophone derivative (6), jatrophone (3), jatropholone A (4) and jatropholone B (5), acetyl aleuritolic acid (1), cyperenoic acid (2) and a monoterpene were isolated from the rhizomes of the Paraguayan crude drug Jatropha isabelli. The compounds were characterized by spectroscopic means. The gastroprotective effect of jatrophone, jatropholone A and B as well as 9beta,13alpha-dihydroxyisabellione 6 and the triterpene 1 was assessed in the HCl/EtOH-induced gastric lesions model in mice. Jatrophone elicited a strong gastroprotective effect with no significant differences between 25, 50 or 100 mg/kg and reducing lesions from 88 to 93%. The jatropholones A and B showed remarkable differences in the gastroprotective assay. Jatropholone A presented a dose-related response, with maximum effect (54% lesion reduction) at the highest dose (100 mg/kg), jatropholone B showed a strong action at all the doses, reducing lesions by 83-91%. The cytotoxicity of the compounds was assessed towards fibroblasts and AGS cells. Jatrophone was toxic against both cell lines (IC50 values: 2.8 and 2.5 microM, respectively). Jatropholone B (5) was not cytotoxic while jatropholone A (4) displayed a selective effect against AGS cells (IC50: 49 microM). The relevance of stereochemistry in the biological effects is clear comparing the effect of jatropholone A and B against AGS cells, with IC50 values of 49 and > 1000 microM for the beta and alpha C-16 isomers, respectively. The results provide scientific support for the use of "yagua rova" as a gastroprotective crude drug in Paraguayan traditional medicine.

Gastroprotective and ulcer healing effect of ferruginol in mice and rats: assessment of its mechanism of action using in vitro models

The gastroprotective activity of the diterpene ferruginol isolated from Prumnopitys andina wood and bark was determined on HCl/EtOH-induced gastric lesions in mice. The effect of the compound on the healing of subacute gastric lesions in rats was also studied. The mode of action of the diterpene was assessed using human gastric epithelial cells (AGS) and MRC-5 fibroblasts. The effect of ferruginol on the prostaglandin E2 content, protection against sodium taurocholate induced-damage and reduced glutathione content was evaluated on AGS cells as well as on the growth of AGS and fibroblast cultures. The free radical scavenging effect of ferruginol was assessed by the 1,1-diphenyl-2-picryl-hydrazil radical and superoxide anion assays. The effect of ferruginol on human erythrocyte membrane lipoperoxidation was determined. The cytotoxicity of the compound was assessed by means of the neutral red uptake. At 25 mg/kg, ferruginol inhibited the appearance of gastric lesions by 60% showing similar effects than lansoprazole at 20 mg/kg. Additionally, the compound displayed a significant ulcer healing activity in rats at 25 and 50 mg/kg with curative ratios of 36.0% and 92.5%, respectively, while the reference compound ranitidine at 50 mg/kg showed a curative ratio of 79.6%. At 6 and 12 microM, ferruginol increased significantly the prostaglandin E2 content. A strong inhibition of lipoperoxidation was found (IC50: 1.4 microM), but no effect was observed on the sodium taurocholate induced-damage or reduced glutathione content. Ferruginol stimulated cell proliferation at 1-2 microM in AGS cells and at 4-8 microM in fibroblasts, with cytotoxicities (IC50) of 24 and 26 microM, respectively. Our results support that ferruginol acts as gastroprotective increasing the PGs content, protecting the cells against lipid peroxidation and improving the gastric ulcer healing by a stimulating effect on the cell proliferation. These findings encourage further pharmacological studies of ferruginol as a potential new anti-ulcerogenic drug.

Gastroprotective effect of the Mapuche crude drug Araucaria araucana resin and its main constituents

The resin from the tree Araucaria araucana (Araucariaceae) has been used since pre-columbian times by the Mapuche amerindians to treat ulcers. The gastroprotective effect of the resin was assessed in the ethanol-HCl-induced gastric ulcer in mice showing a dose-dependent gastroprotective activity at 100, 200 and 300 mg/kg per os. The main three diterpene constituents of the resin, namely imbricatolic acid, 15-hydroxyimbricatolal and 15-acetoxyimbricatolic acid were isolated and evaluated for gastroprotective effect at doses of 50, 100 and 200 mg/kg. A dose-related gastroprotective effect with highly significant activity (P<0.01) was observed at doses up to 200 mg/kg. At 100 mg/kg, the highest gastroprotective activity was provided by 15-hydroxyimbricatolal and 15-acetoxyimbricatolic acid, all of them being as active as the reference drug lansoprazole at 20 mg/kg. The cytotoxicity of the main diterpenes as well as lansoprazole was studied towards human lung fibroblasts (MRC-5) and determined by the MTT reduction assay. A concentration-dependent cell viability inhibition was found with IC50 values ranging from 125 up to 290 microM. Our results support the traditional use of the Araucaria araucana resin by the Mapuche culture.

Gastroprotective and ulcer-healing effect of new solidagenone derivatives in human cell cultures

The labdane diterpene solidagenone 1 and its semisynthetic and biotransformation derivatives 2-10 were assessed for gastroprotective and ulcer-healing effect using human epithelial gastric cells (AGS) and human lung fibroblasts (MRC-5). The ability of the compounds to protect the AGS cells against the damage induced by sodium taurocholate (NaT), to stimulate the cellular reduced glutathione (GSH), prostaglandin E(2) content, enhance AGS and MRC-5 cell proliferation and to scavenge superoxide anion in vitro was studied. The cytotoxicity of the compounds was assessed towards MRC-5 fibroblasts and AGS cells. A significant reduction of cell damage after NaT incubation was observed when the AGS cells were pretreated with compounds 2 and 6. Treatment with compounds 4-6, 8 and 9 significantly stimulated the GSH content in AGS cell cultures. None of the studied compounds was active as a superoxide anion scavenger. In AGS cells treated with compounds 1-10, only compound 5 was able to increase prostaglandin content. Concerning the proliferation assays, a significant stimulating effect was observed for compounds 2, 8, 9 on AGS cells and for 5, 7-9 on MRC-5 fibroblasts. Regarding cytotoxicity, solidagenone showed higher toxicity while compounds 4 and 7 were the less toxic. Our results showed that most of the studied compounds act in vitro as gastroprotectors increasing the cellular GSH content. Additionally, some derivatives exhibited in vitro ulcer-healing effect stimulating the cell proliferation.

Traditional medicine and gastroprotective crude drugs

A frequent question when dealing with the search for gastroprotective compounds from natural sources is how far or close are both the plant preparations and extract amounts from the doses recommended in traditional medicine and what should be considered realistic levels for experimental studies. The administration way is oral and therefore extracts and products should be administered by gavage when looking for validation of ethnopharmacological uses. Suggestions of doses for both crude extracts and pure compounds are presented and discussed. For plant extracts prepared from single herbs and herbal mixtures, dose-response studies in the range between 100 and 300 mg/kg are suggested, with more than a single gastric ulcer model either in rats or mice. A suitable reference compound should be used according to the ulcer model and in doses resembling those used for human patients. For pure compounds and structure-activity studies or trends, dose-response results should be provided for at least a parent compound in order to select a reasonable dose for comparison purposes. We suggest an evaluation of the activity of the parent compound in the 50-300 mg/kg range and to look for structural modification leading to derivatives with similar or higher gastroprotective effects than the reference antiulcer compounds.