Protective effects of polygodial and related compounds on ethanol-induced gastric mucosal lesions in rats: structural requirements and mode of action

Absolute configuration and antileishmanial activity of (-)-cyclocolorenone isolated from Duguetia lanceolata (Annonaceae)

BACKGROUND

The fractionation of the n-hexane phase of the EtOH extract from the leaves of Duguetia lanceolata (Annonaceae) led to the identification of the sesquiterpene (-)- cyclocolorenone.

OBJECTIVE

Chemical characterization, including determination of the absolute stereochemistry, and in vitro evaluation of antileishmanial activity of the sesquiterpene (-)-cyclocolorenone, isolated from D. lanceolata were carried out.

METHODS

(-)-Cyclocolorenone was isolated from D. lanceolata leaves using different chromatographic steps and its structure was defined by analysis of NMR and ESI-HRMS data. Additionally, the absolute configuration of (-)-cyclocolorenone was ambiguously assigned by means of vibrational circular dichroism (VCD). Antileishmanial activity of (-)-cyclocolorenone was evaluated on promastigote and amastigote forms of Leishmania (Leishmania) amazonensis. The integrity of the cell membrane of L. (L.) amazonensis was analyzed using the SYTOX green probe.

RESULTS

(-)-(1R,6S,7R,10R)-Cyclocolorenone displayed activity against promastigotes and amastigotes forms of L. (L.) amazonensis with IC50 of 4.54 and 28.44 , respectively. Furthermore, this compound was non-toxic in J774 macrophage cells (CC50 > 458.71 ) with a selectivity index > 100 (promastigotes) and > 32.2 (amastigotes). Additionally, (-)-cyclocolorenone was observed to target the parasite cell membrane.

CONCLUSION

Obtained data suggested that (-)-cyclocolorenone, in which absolute configuration was determined, can be considered as a scaffold for the development of new drugs for the treatment of leishmaniasis.

Polysaccharides of Dendrobium officinale Kimura & Migo Leaves Protect Against Ethanol-Induced Gastric Mucosal Injury via the AMPK/mTOR Signaling Pathway in Vitro and vivo

Ethanol-induced gastric mucosal injury is a common gastrointestinal disorder. Polysaccharides separated from herbs have been shown to be effective for ethanol-induced gastric mucosal injury, but whether the polysaccharides from Dendrobium officinale Kimura & Migo leaves (LDOP-1) protected mucosa from ethanol-induced injury remains unknown. Thus, the present study carried out gastric mucosal protection and the mechanism of LDOP-1 in vivo and vitro. The chemical composition of LDOP-1 was a heteropolysaccharide comprising mannose, galacturonic acid, glucose, galactose, and arabinose at a molar ratio of 2.0:1.1:0.7:0.5:0.4. Pharmacological results showed that LDOP-1 significantly reduced gastric mucosal injury score and pathological injury, improved antioxidant capacity, reduced the level of reactive oxygen species, and reversed the apoptosis of GES-1 in vivo and vitro. Research showed that LDOP-1 pretreatment upregulated the expression level of p-AMPK, LC3β, HO-1, and Beclin-1; downregulated the expression level of p-mTOR and p62; and reversed the expression level of caspase3, Bax, and Bcl-2. This study was the first to demonstrate that LDOP-1 could protect against ethanol-induced gastric mucosal injury via the AMPK/mTOR signaling pathway in vitro and vivo.

Isolation, Gastroprotective Effects and Untargeted Metabolomics Analysis of Lycium Minutifolium J. Remy (Solanaceae)

Lycium minutifolium J. Remy (Solanaceae) is commonly used as an infusion in traditional medicine to treat stomach pain, meteorism, intestinal disorders, stomach ailments, and other severe problems including prostate cancer and stomach cancer. From the EtOAc extract of L. minutifolium bark five known metabolites were isolated using chromatographic techniques. The gastroprotective effects of the EtOAc fraction and edible infusion extract of the bark were assayed on the hydrochloric acid (HCl)/EtOH induced gastric ulcer model in mice to support the traditional use of the plant. The EtOAc extract and the edible infusion showed gastroprotective effect at dose of 100 mg/kg reducing lesions by 31% and 64%, respectively. The gastroprotective action mechanisms of the edible infusion at a single oral dose of 100 mg/kg were evaluated suggesting that prostaglandins, sulfhydryl groups, and nitric oxide are involved in the mode of gastroprotective action. The UHPLC analysis coupled to high-resolution mass spectrometry of the edible infusion showed the presence of twenty-three compounds. Our results can support the gastroprotective properties of the edible infusion extract, and at least can validate in part, the ethnopharmacological uses of the plant.

Corryocactus brevistylus (K. Schum. ex Vaupel) Britton & Rose (Cactaceae): Antioxidant, Gastroprotective Effects, and Metabolomic Profiling by Ultrahigh-Pressure Liquid Chromatography and Electrospray High Resolution Orbitrap Tandem Mass Spectrometry

Corryocactus brevistylus (K. Schum. ex Vaupel) Britton & Rose (Cactaceae) is a shrubby or often arborescent cactus popularly known as "sancayo" and produce an edible fruit known as "Sanky" which is consumed in Arequipa-Perú. The purpose of this study was to report the gastroprotective activity and relate this activity to the antioxidant capacity and presence of phenolic compounds for the first time. A metabolomic profiling based on Ultrahigh-pressure liquid chromatography and electrospray high resolution mass spectrometry, and the antioxidant activities (DPPH, ABTS, and FRAP), ascorbic acid content, total phenolics and flavonoids contents, and the mode of gastroprotective action of the Sanky fruit including the involvement of prostaglandins, nitric oxide, and sulfhydryl compounds is reported. Thirty-eight compounds were detected in the ethanolic extract including 12 organic acids, nine hydroxycinnamic acids, three isoamericanol derivatives, six flavonoids, five fatty acids, and two sterols. The results of the biological tests showed that the ethanolic extract had antioxidant capacity and gastroprotective activity on the model of HCl/EtOH-induced gastric lesions in mice (at 10, 25, 50, and 100 mg/kg). The effect elicited by the extract at 50 mg/kg was reversed by indometacin and N-ethylmaleimide but not by N^G-nitro-L-arginine methyl ester suggesting that sulfhydryl groups and prostaglandins are involved in the mode of gastroprotective action. In conclusion, our study proves that C. brevistylus pears have some gastroprotective and antioxidant capacities and consumption is recommended for the presence of several bioactive compounds.

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.

Gastroprotective Activity of Parastrephia quadrangularis (Meyen), Cabrera from the Atacama Desert

Forty-three metabolites including several methoxylated flavonoids, tremetones, and ent-clerodane diterpenes were accurately identified for the first time in the ethanolic extract of P. quadrangularis by means of hyphenated UHPLC-quadrupole Orbitrap mass spectrometry, and seven isolated compounds were tested regarding gastroprotective activity using the HCl/EtOH-induced lesion model in mice. A new tremetone (compound 6) is reported based on spectroscopic evidence. The isolated clerodanes and tremetones showed gastroprotective activity in a mouse model, evidenced by compound 7 (p-coumaroyloxytremetone), which showed the highest gastroprotective activity (76%), which was higher than the control drug lansoprazole (72%). Our findings revealed that several constituents of this plant have gastroprotective activity, and particularly, p-coumaroyloxytremetone could be considered as a lead molecule to explore new gastroprotective agents. This plant is a rich source of biologically active tremetones and terpenoids which can support the ethnobotanical use of the plant.

Structure-Pungency Relationships and TRP Channel Activation of Drimane Sesquiterpenes in Tasmanian Pepper (Tasmannia lanceolata)

Sensory-guided fractionation of extracts of Tasmanian pepper berries revealed 20 drimane sesquiterpens, among which polygodial, warburganal, and 1β-acetoxy-9-deoxy-isomuzigadial exhibited the lowest pungency threshold concentrations on the tongue surface (0.6-2.8 nmol/cm²) and elicited a dose-dependent calcium influx into mTRPA1 expressing CHO cells with the lowest EC₅₀ values (4.5 ± 1.0 to 16.7 ± 7.5 μmol/L) and a good correlation to oral pungency thresholds (R² = 0.986, linear regression). Calcium imaging assays demonstrated these chemosensates to induce a calcium influx into cultured trigeminal neurons prepared from wildtype (TRPA1^+/+) mice, whereas no calcium influx was observed in neurons from TRPA1 knockout mice (TRPA1^-/-), thus confirming the α,β-unsaturated 1,4-dialdehyde structure to be the required structural motif for a low oral puncency thresholds and activation of the Transient Receptor Potential Channel A1 (TRPA1). Time-resolved NMR experiments confirmed the pungency mediating mechanism for electrophilic drimane sesquiterpene dialdehydes to be different from that found for other electrophilic pungent agents like isothiocyanates, which have been shown to undergo a covalent binding with cysteine residues in TRPA1. Instead, the high-impact chemosensates polygodial, warburganal, and 1β-acetoxy-9-deoxy-isomuzigadial showed immediate reactivity with the ε-amino group of lysine side chains to give pyrrole-type conjugates, thus showing evidence for TRPA1 activation by covalent lysine modification.

Gastroprotective activity of synthetic coumarins: Role of endogenous prostaglandins, nitric oxide, non-protein sulfhydryls and vanilloid receptors

Natural or synthetic coumarins showed gastroprotective and antiulcer activity in animal models. In this study, we have synthetized twenty coumarins using classic methods to evaluate their gastroprotective effects on the ethanol/HCl-induced gastric lesion model in mice at 20mg/kg. Among the coumarins synthetized, compounds 6 and 10 showed the greatest gastroprotective activity being as active as lansoprazole at 20mg/kg and reducing gastric lesions by 75 and 76%, respectively. Then, in a second experiment, compounds 6 and 10 were re-evaluated in order to understand the possible mode of gastroprotective activity. Regarding coumarin 6, the protective effect was reduced by pre-treatment of the mice with N-ethylmaleimide and l-NAME suggesting that sulfhydryl compounds and endogenous nitric oxide are involved in its gastroprotective activity. While for coumarin 10 the effect was reduced by pre-treatment with indomethacin suggesting that prostaglandins are positively involved in its gastroprotective activity.

Further drimane sesquiterpenes from Drimys brasiliensis stem barks with cytotoxic potential

Drimys brasiliensis Miers (Winteraceae) is used in folk medicine for the treatment of cancer. Its anti-tumor activity has been demonstrated in vitro models using extracts and isolated compounds. This study investigates the cytotoxic effects of stem bark extracts of D. brasiliensis as well as isolated compounds that may be responsible for the activitys and evaluates them in leukemia cells. The stem bark extract were subjected to column chromatography, and the structures of compounds were elucidated based on spectroscopic methods by using NMR and infrared spectroscopy and GC/MS. The cytotoxicity of the isolated compounds was evaluated in chronic myeloid (K562) and acute B lymphoblastic (Nalm6) leukemia cells using tetrazolium assay (MTT). Two new compounds were isolated 1β-O-p-methoxy-E-cinnamoyl-5α-keto-11α-enol-albicanol (1a) and the isomer 1β-O-p-methoxy-E-cinnamoyl-5α-keto-11β-enol-albicanol (1b) and 1β-O-p-methoxy-E-cinnamoyl-isodrimeninol (2). The known compounds polygonal acid (3a) and the isomer isopolygonal acid (3b), fuegin (4a) and the isomer epifuegin (4b), the mixture drimanial (5) and 1β-O-(p-methoxy-E-cinnamoyl)-6α-hydroxypolygodial (6) were also isolated. The drimanes (1-4) and drimanial (5), 1β-(p-coumaroyloxy)-polygodial (7), 1β-(p-methoxycinnamoyl)-polygodial (8), and polygodial (9) isolated previously were assessed in tumor cells. The IC50 values were between 3.56 and 128.91 μM. 1-β-(p-cumaroiloxi)-polygodial showed the best result with IC50 8.18 and 3.56 μM by K562 and Nalm6, respectively. The chloroform extract of the stem bark of D. brasiliensis is a great source of drimane sesquiterpenes. Our experimental data suggest that drimanes are responsible for cytotoxicity activity demonstrated by this species, especially those with the aldehyde group linked to carbons C-11 and C-12.

An unusual mulinane diterpenoid from the Chilean plant Azorella trifurcata (Gaertn) Pers

Four new mulinane-type diterpenoids besides the known compounds mulin-11,13-dien-20-oic acid, 13α-hydroxyazorellane, 13β-hydroxyazorellane, mulinolic acid, azorellanol, and mulin-11,13-dien-18-acetoxy-16,20-dioic acid were isolated from the Chilean plant Azorella trifurcata. One of the new metabolites isolated, 7α-acetoxy-9-epi-13β-hydroxymulinane, possesses a new trans-syn-trans arrangement in a tricyclic ring system not previously encountered in nature. Among the mulinane diterpenoids isolated, mulin-11,13-dien-20-oic acid showed the gastroprotective effect on HCl-EtOH-induced gastric lesions in mice (ED50 = 55 mg kg(-1)). Regarding the mode of gastroprotective action for this active compound, its effect was reduced by pre-treatment of the mice with indomethacin and N-ethylmaleimide, suggesting that prostaglandins and sulfhydryl compounds are positively involved in the gastroprotective activity using this model.

Screening for antioxidant and detoxification responses in Perna canaliculus Gmelin exposed to an antifouling bioactive intended for use in aquaculture

Polygodial is a drimane sesquiterpene dialdehyde derived from certain terrestrial plant species that potently inhibits ascidian metamorphosis, and thus has potential for controlling fouling ascidians in bivalve aquaculture. The current study examined the effects of polygodial on a range of biochemical biomarkers of oxidative stress and detoxification effort in the gills of adult Perna canaliculus Gmelin. Despite high statistical power and the success of positive controls, the antioxidant enzymes glutathione reductase (GR), glutathione peroxidase (GPOX), catalase (CAT), and superoxide dismutase (SOD); thiol status, as measured by total glutathione (GSH-t), glutathione disulphide (GSSG), and GSH-t/GSSG ratio; end products of oxidative damage, lipid hydroperoxides (LHPO) and protein carbonyls; and detoxification pathways, represented by GSH-t and glutathione S-transferase (GST), were unaffected in the gills of adult P. canaliculus exposed to polygodial at 0.1 or 1 × the 99% effective dose in fouling ascidians (IC₉₉). Similarly, GR levels, thiol status, and detoxification activities were unaffected in mussels exposed to polygodial at 10 × the IC₉₉, although GPOX, CAT, and SOD activities increased. However, the increases were small relative to positive controls, no corresponding oxidative damage was detected, and this concentration greatly exceeds effective doses required to inhibit fouling ascidians in aquaculture. These findings compliment a previous study that established the insensitivity to polygodial of P. canaliculus growth, condition, and mitochondrial functioning, providing additional support for the suitability of polygodial for use as an antifouling agent in bivalve aquaculture.

Diterpenylquinone hybrids: synthesis and assessment of gastroprotective mechanisms of action in human cells

A modern approach in the search for new bioactive molecules is the synthesis of novel chemical entities combining molecules of different biosynthetic origin presenting biological effects as single compounds. Gastroprotective compounds from South American medicinal plants, namely quinones and diterpenes, were used as building blocks to obtain hybrid diterpenylquinones. Starting from the labdane diterpene junicedric acid and two isomers, as well as from three quinones, including lapachol, 18 hybrid molecules were synthesized. Six of them are described for the first time. The potential gastroprotective mechanisms of action of the compounds were assessed in dose-response experiments using human gastric epithelial cells (AGS) and human lung fibroblasts (MRC-5). The following studies were carried out: stimulation of cell proliferation, cytoprotection against sodium taurocholate (NaT)-induced damage, synthesis of PGE₂ and total reduced sulfhydryl (GSH) content. The antioxidant capacity of the compounds was determined on the inhibition of the lipoperoxidation in human erythrocyte membranes. Hybrid compounds presented activities different from those shown by the starting compounds, supporting the potential of this approach in the search for new bioactive molecules. The effects might be modulated by selective modification in the terpene or quinone moieties of the new molecules. Structure-activity relationships are discussed.

Further mulinane diterpenoids from Azorella compacta

OBJECTIVES

The chemical study of a dichloromethane extract from Azorella compacta was directed to the isolation of characteristic mulinane and azorellane diterpenoids in order to determine their gastroprotective activity.

METHODS

Usual chromatographic techniques on the extract led to the isolation of 12 compounds, which were identified by their spectroscopic properties. The HCl/ethanol-induced gastric lesions model in mice was used to determine the gastroprotective activity.

KEY FINDINGS

The new diterpenoids, 13β-hydroxymulinane (1), mulin-11,13-dien-20-ol (2), 13α-methoxyazorellanol (3) and mulin-11,13-dien-18-acetoxy-16,20-dioic acid (12) were isolated from A. compacta. The known diterpenoids mulin-11,13-dien-20-oic acid (4), 13α-hydroxyazorellane (5), 13β-hydroxyazorellane (6), mulinic acid (7), mulinolic acid (8) and azorellanol (9), and the aromatic compounds 5,7-dihydroxychromone (10) and isoflavonoid biochanin A (11), were also obtained from the extract. Compounds 6, 9 and 12 at 20 mg/kg reduced gastric lesions by 69%, 71% and 73%, respectively, being statistically similar to lansoprazole at the same dose.

CONCLUSIONS

The results corroborate the intraspecific chemical variations detected previously in specimens of A. compacta collected at different Chilean latitudes. A high concentration of azorellanol (9) could account in part for some of the therapeutic properties attributed to this species, in particular in ulcer treatment. Most of the mulinane and azorellane diterpenoids isolated in this study showed relevant gastroprotective activity at a low dose in the bioassay.

Comparative study on the larvicidal activity of drimane sesquiterpenes and nordrimane compounds against Drosophila melanogaster til-til

Natural compounds from Drimys winteri Forst and derivatives exhibited larvicidal effects against Drosophila melanogaster til-til. The most active compound was isodrimenin (4). The highest lethal concentration to the larvae of D. melanogaster was 4.5 ± 0.8 mg/L. At very low concentrations drimenol (1), confertifolin (3), and drimanol (5) displayed antifeedant and larvae growth regulatory activity. The antifeedant results of nordrimanic and drimanic compounds were better in first instar larvae. The EC₅₀ value of polygodial (2) was 60.0 ± 4.2 mg/L; of diol 15 45.0 ± 2.8 mg/L, and of diol 17 36.9 ± 3.7 mg/L, while the new nordrimane compound 12 presented a value of 83.2 ± 3.5 mg/L.

Structural requirements for the antifungal activities of natural drimane sesquiterpenes and analogues, supported by conformational and electronic studies

Seventeen drimanes including polygodial (1), isopolygodial (2), drimenol (3) and confertifolin (4) obtained from natural sources and the semi-synthetic derivatives 5–17 obtained from 1–3, were evaluated in vitro for antifungal properties against a unique panel of fungi with standardized procedures by using two end-points, MIC₁₀₀ and MIC₅₀. A SAR analysis of the whole series, supported by conformational and electronic studies, allowed us to show that the Δ^7,8 -double bond would be one of the key structural features related to the antifungal activity. The MEPs obtained for active compounds exhibit a clear negative minimum value (deep red zone) in the vicinity of the Δ^7,8 -double bond, which is not present in the inactive ones. Apart of this negative zone, a positive region (deep blue) appears in 1, which is not observed either in its epimer 2 nor in the rest of the active compounds. The LogP of active compounds varies between 2.33 and 3.84, but differences in MICs are not correlated with concomitant variations in LogP values.

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 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 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 < 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.

Gastroprotective activity of isopulegol on experimentally induced gastric lesions in mice: investigation of possible mechanisms of action

The present study investigated whether isopulegol, a monoterpene present in essential oils of several aromatic plants, would be able to promote some gastroprotective effect and also verified the possible mechanisms involved in this action. For this study, ethanol- and indomethacin-induced gastric ulcer models in mice and histopathological assessment were used. The roles of NO, sulfhydryls (glutathione, GSH), ATP-sensitive K(+) channels (K(ATP) channels), and prostaglandins were also investigated. Isopulegol exhibited a dose-related gastroprotective effect against ethanol-induced lesions, while the pretreatment with glibenclamide and indomethacin [but not with N(G)-nitro-L-arginine methyl ester] were able to reverse this action. The pretreatment with isopulegol also restored GSH levels to normal levels and exhibited dose-related gastroprotective effect against indomethacin-induced ulcer. The results suggested that isopulegol presents significant gastroprotective effects in both ethanol- and indomethacin-induced ulcer models, which appear to be mediated, at least in part, by endogenous prostaglandins, K(ATP) channel opening, and antioxidant properties.

Medicinal flowers. XVI. New dammarane-type triterpene tetraglycosides and gastroprotective principles from flower buds of Panax ginseng

The oligoglycoside fraction from the flower buds of Panax ginseng C. A. MEYER (Araliaceae) was found to show protective effects on ethanol-induced gastric mucosal lesions in rats. From the oligoglycoside fraction, new dammarane-type triterpene tetraglycosides, floralginsenosides M, N, O, and P, were isolated together with the major oligoglycosides ginsenoside Rd and Re. The structures of the new floralginsenosides were elucidated on the basis of chemical and physicochemical evidence. Ginsenoside Rd (protopanaxadiol 3,20-O-bisdesmoside) exhibited inhibitory effects on ethanol- and indomethacin-induced gastric mucosal lesions in rats.

Gastroprotective activity and cytotoxic effect of cyperenoic acid derivatives

The gastroprotective effect of the sesquiterpene cyperenoic acid and seven semi-synthetic derivatives was assessed in the HCl/ethanol-induced gastric ulcer model in mice. At doses of 25, 50 and 100 mg kg(-1), cyperenoic acid showed a dose-dependent gastroprotective effect reducing the lesions by 45 and 75% at 50 and 100 mg kg(-1), respectively. Seven derivatives of the sesquiterpene were prepared and their gastroprotective activity compared at 50 mg kg(-1). The cytotoxicity of the compounds was evaluated in fibroblasts and AGS cells. At 50 mg kg(-1), patchoulan-15-oic acid (compound 8) presented the best gastroprotective effect, reducing the gastric lesions by 86%, with a similar effect to lansoprazole at 20 mg kg(-1). The gastroprotective effect of cyperenol, cyperenoic acid methyl ester and the ethylamide and butylamide from cyperenoic acid were in the same range, reducing the gastric lesions by 72-77%. Cyperenol and cyperenoic acid methyl ester, however, were more cytotoxic with IC50 (concentration that produces a 50% inhibitory effect) values of 44 and 75, 48 and 75 microM against AGS cells and fibroblasts, respectively. The best gastroprotective effect with lower cytotoxicity was found for the compound 8, cyperenoic acid and the p-anisidyl derivative 7.

Gastroprotective and ulcer-healing activity of oleanolic acid derivatives: In vitro–in vivo relationships

The triterpene oleanolic acid 1 and its semisynthetic derivatives 2-7 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) and prostaglandin E(2) content, to 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 and AGS cells. In addition, the gastroprotective activity of the compounds was assessed in vivo using the HCl/EtOH-induced ulcer model in mice. All the assayed compounds displayed a significant reduction of AGS cells damage after incubation with NaT. None of the studied compounds was active as a superoxide anion scavenger nor stimulated the GSH content in AGS cell cultures. Compounds 1, 2, 4 and 6 were able to increase the prostaglandin content in AGS cell cultures. Concerning the proliferation assays, a significant stimulating effect was observed for compounds 3 and 7 on AGS cells and for 1 and 7 on MRC-5 fibroblasts. Regarding cytotoxicity, derivatives 2, 4, 6 and 7 were less toxic than the parent compound oleanolic acid. Our results strongly support the predictive capacity of the in vitro assessment of gastroprotective activity allowing the reduction of experimental animals.

Subchronic toxicity study of water pepper extract in F344 rats

A subchronic toxicity study of water pepper extract (WPE) from Polygonum hydropiper L. was conducted in groups of 10 male and 10 female F344 rats fed powdered diets containing 0, 62.5, 250, 1000 or 4000 ppm concentrations for 13 weeks. Suppression of body weight gain due to decreased food consumption was observed in both sexes at 4000 ppm, and at autopsy, increase of relative weights was observed for the brain, liver, spleen, kidneys, and testes in these animals, suggestive of the reflection of the reduced body weights. At this dose, slight increases of blood urea nitrogen in both sexes and serum alanine aminotransferase, Na and Cl in females, were observed, suggestive of weak hepatic and renal toxicity, at least in females. The same females also exhibited slight decrease of red blood cells and haematocrit, slight increase of mean corpuscular volume and mean corpuscular haemoglobin, and minimal increase of splenic haemosiderin deposition, providing evidence of slight haemolytic anemia. On the other hand, enhanced accumulation of mast cells was observed in the mesenteric lymph nodes at 4000 ppm in males and 1000 and 4000 ppm in females. Considering the anti-anaphylactic properties of polygodial, a major constituent of WPE, the mast cell accumulation was concluded to be an adaptive change in response to the subchronic oral administration of WPE. Based on the present toxicity data, 1000 ppm was determined to be the no-observed-adverse-effect level, translating into 57.4 and 62.9 mg/kg/day for male and female rats, respectively.

Triterpene saponins with gastroprotective effects from tea seed (the seeds of Camellia sinensis)

Six new triterpene saponins, theasaponins A(1) (1), A(2) (2), A(3) (3), F(1) (4), F(2) (5), and F(3) (6), were isolated from the saponin fraction of the seeds of Camellia sinensis. The stereostructures of 1-6 were elucidated on the basis of chemical and physicochemical evidence. Theasaponin A(2) (2) showed an inhibitory effect on ethanol-induced gastric mucosal lesions in rats at a dose of 5.0 mg/kg, p.o., and its activity was more potent than that of omeplazole. Structure-activity relationships for theasaponins on ethanol-induced gastroprotective activities may be suggested as follows: (1) the 28-acetyl moiety enhances activity; (2) theasaponins having a 23-aldehyde group exhibit more potent activities than those with a 23-hydroxymethyl group or a 23-methoxycarbonyl group.

The vanilloid receptor as a putative target of diverse chemicals in multiple chemical sensitivity

The vanilloid receptor (TRPV1 or VR1), widely distributed in the central and peripheral nervous system, is activated by a broad range of chemicals similar to those implicated in Multiple Chemical Sensitivity (MCS) Syndrome. The vanilloid receptor is reportedly hyperresponsive in MCS and can increase nitric oxide levels and stimulate N-methyl-D-aspartate (NMDA) receptor activity, both of which are important features in the previously proposed central role of nitric oxide and NMDA receptors in MCS. Vanilloid receptor activity is markedly altered by multiple mechanisms, possibly providing an explanation for the increased activity in MCS and symptom masking by previous chemical exposure. Activation of this receptor by certain mycotoxins may account for some cases of sick building syndrome, a frequent precursor of MCS. Twelve types of evidence implicate the vanilloid receptor as the major target of chemicals, including volatile organic solvents (but not pesticides) in MCS.

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 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.

Bioactive Saponins and Glycosides. XXIII. Triterpene Saponins with Gastroprotective Effect from the Seeds of Camellia sinensis-Theasaponins E3, E4, E5, E6, and E7-

The saponin fraction from the seeds of the tea plant [Camellia sinensis (L.) O. KUNTZE (Theaceae)] was found to exhibit potent protective effects on ethanol- and indomethacin-induced gastric mucosal lesions in rats. Five new triterpene saponins, theasaponins E3 (1), E4 (2), E5 (3), E6 (4), and E7 (5), were isolated together with 11 known saponins from the saponin fraction. The chemical structures of 1-5 were elucidated on the basis of chemical and physicochemical evidence. Among the isolated saponins, theasaponins E1 (6), E2 (7), and E5 (3) and assamsaponin C (10) showed an inhibitory effect on ethanol-induced gastric mucosal lesions at a dose of 5.0 mg/kg, p.o. and their activities were stronger than that of omeplazole. With regard to the structure-activity relationships of theasaponins, the following structural requirements for a protective effect on ethanol-induced gastric lesions were suggested; 1) the 21- and/or 22-acyl groups are essential for the activity, 2) acetylation of the 16-hydroxyl group reduce the activity.

Gastroprotective effects of phenylpropanoids from the rhizomes of Alpinia galanga in rats: structural requirements and mode of action

The effects of 1'S-1'-acetoxychavicol acetate and related phenylpropanoids isolated from the rhizomes of Alpinia galanga on ethanol-induced gastric lesions in rats were examined. Among them, 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate markedly inhibited the ethanol-induced gastric mucosal lesions (ED(50)=0.61 and ca. 0.90 mg/kg). In addition, 1'S-1'-acetoxychavicol acetate inhibited the lesions induced by 0.6 M HCl (ED(50)=0.73 mg/kg) and aspirin (ED(50)=0.69 mg/kg) but it did not show a significant effect on indomethacin-induced gastric lesions and acid output in pylorus-ligated rats at doses of 0.5-5.0 mg/kg. From the gastroprotective effects of various related compounds, the 1'-acetoxyl group of 1'S-1'-acetoxychavicol acetate and 1'S-1'-acetoxyeugenol acetate was found to be essential for their strong activity. With regard to the mode of action, the gastroprotective effects of 1'S-1'-acetoxychavicol acetate were attenuated by pretreatment with indomethacin and N-ethylmaleimide, and 1'S-1'-acetoxychavicol acetate significantly increased the glutathione levels of gastric mucosa in rats. These findings suggest that endogenous prostaglandins and sulfhydryl compounds are involved in the protective effect of 1'S-1'-acetoxychavicol acetate.

Protective effects of polygodial on gastric mucosal lesions induced by necrotizing agents in rats and the possible mechanisms of action

The effects of polygodial isolated from the leaves of Tasmannia lanceolata on necrotizing agents-induced gastric lesions in rats were compared with capsaicin. Polygodial markedly inhibited the gastric mucosal lesions induced by several necrotizing agents, such as ethanol (ED(50)=0.029 mg/kg, p.o.), 0.6 M HCl (ED(50)=0.26 mg/kg, p.o.), and aspirin (ED(50)=0.38 mg/kg, p.o.), and partly inhibited the gastric mucosal lesions induced by indomethacin, but showed no significant effect on acid output in pylorus-ligated rats at doses of 0.05-0.5 mg/kg. The gastroprotection of polygodial was attenuated by pretreatment with indomethacin (10 mg/kg, s.c.), N(G)-nitro-L-arginine methyl ester (70 mg/kg, i.p.), N-ethylmaleimide (10 mg/kg, s.c.) and ruthenium red (3.5 mg/kg, s.c.). Polygodial (0.2 mg/kg, p.o.) increased the amount of reduced glutathione in gastric mucosa of ethanol-treated group. These results suggested that endogenous prostaglandins, nitric oxide, sulfhydryl compounds and vanilloid receptor-mediated effects are involved in the protective effect of polygodial.

Protective effects of steroid saponins from Paris polyphylla var. yunnanensis on ethanol- or indomethacin-induced gastric mucosal lesions in rats: structural requirement for activity and mode of action

The methanolic extract from the rhizomes of Paris polyphylla SM. var. yunnanensis (FR.) H-M. was found to potently inhibit ethanol-induced gastric lesions in rats. Through bioassay-guided separation, four known spirostanol-type steroid saponins, pennogenin 3-O-alpha-L-rhamnopyranosyl(1-->2)-[alpha-L-arabinofuranosyl(1-->4)]-beta-D-glucopyranoside (1), pennogenin 3-O-alpha-L-rhamnopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D-glucopyranoside (2), diosgenin 3-O-alpha-L-rhamnopyranosyl(1-->2)-[alpha-L-arabinofuranosyl(1-->4)]-beta-D-glucopyranoside (3), and diosgenin 3-O-alpha-L-rhamnopyranosyl(1-->4)-alpha-L-rhamnopyranosyl(1-->4)-[alpha-L-rhamnopyranosyl(1-->2)]-beta-D-glucopyranoside (4), and a new furostanol-type steroid saponin, parisaponin I (5), together with two known furostanol-type steroid saponins, trigofoenoside A (6) and protogracillin (7), were isolated from the active fraction. Compounds 1-4 (1.25-10 mg/kg, po) strongly inhibited gastric lesions induced by ethanol and indomethacin. With regard to structural requirement of steroid saponins, the 3-O-glycoside moiety and spirostanol structure were found to be essential for the activity and the 17-hydroxyl group in the aglycon part enhanced the protective effects against ethanol-induced gastric lesions. The protective effects of 1 and 3 against ethanol-induced gastric lesions were attenuated by pretreatment with indomethacin and N-ethylmaleimide. Compounds 1 and 3 weakly inhibited acid secretions in pylorus-ligated rats. These findings suggested that endogenous prostaglandins and sulfhydryl compounds were involved in the protective activity.

Medicinal foodstuffs. XXXI. Structures of new aromatic constituents and inhibitors of degranulation in RBL-2H3 cells from a Japanese folk medicine, the stem bark of Acer nikoense

Four new aromatic constituents, rhododendroketoside, (-)-sakuraresinoside, acernikol, and nikoenoside, were isolated from a Japanese folk medicine, the stem bark of Acer nikoense MAXIM. The structures of the new constituents were determined on the basis of chemical and physicochemical evidence. The principle cyclic diarylheptanoids were found to show inhibitory effects on the release of beta-hexosaminidase in RBL-2H3 cells.