Alejandra O. M. Maria

Antimicrobial activity of Artemisia douglasiana and dehydroleucodine against Helicobacter pylori.

ETHNOPHARMACOLOGICAL RELEVANCE The increasing resistance of Helicobacter pylori to antibiotics demands the search for novel compounds from plant based sources. Artemisia douglasiana Besser is widely used in Cuyo region (Argentina) as folk medicine for the treatment of gastric ailments. AIM OF STUDY Based on our previous studies that Artemisia douglasiana exert cytoprotective actions against ethanol-induced gastric mucosal injury we assayed the anti-Helicobacter pylori effect of the Artemisia douglasiana extract and its active compound, dehydroleucodine. MATERIALS AND METHODS The in vitro anti-bacterial activity of Artemisia douglasiana extract and its active compound, dehydroleucodine were determined against one standard strain and six clinical isolates of Helicobacter pylori by using the agar dilution methods. RESULTS The results showed that both dehydroleucodine and Artemisia douglasiana extract had activity against the microorganism with MICs between 1-8 and 60-120 mg/L, respectively. CONCLUSIONS Artemisia douglasiana may be a useful alternative treatment strategy principally in eradication of metronidazole and clarithromycin-resistant strain.

Protective effect of Artemisia douglasiana Besser extracts in gastric mucosal injury

The aim of this work was to evaluate markers of oxidative stress in ethanol‐induced gastric ulcers and the protective antioxidant activity in‐vivo of Artemisia douglasiana Besser extracts in ethanol‐treated rats. Ethanol‐induced oxidative damage is believed to be associated with generation of reactive oxygen molecules, which leads to oxidative stress. A. douglasiana is used in folk medicine as a cytoprotective agent against peptic ulcer. Different bioassays were performed: in‐vivo stomach chemiluminescence, tert‐butyl hydroperoxide initiated chemiluminescence (in‐vitro chemiluminescence), total antioxidant capacity (TRAP) and catalase, superoxide dismutase (SOD) and glutathione peroxidase (GPx) activity in stomach homogenates. When ethanol (3 g kg−1) was administered, the in‐vivo chemiluminescence increased by 107%, in‐vitro chemiluminescence by 108%, SOD by 130% (P<0.001), and catalase and TRAP decreased by 43 and 59% (P<0.05 and 0.001, respectively). A. douglasiana (400 mg kg−1) pretreatment decreased in‐vivo chemiluminescence by 41% (P<0.05), in‐vitro chemiluminescence by 66% (P<0.001) and SOD by 56% (P<0.001) and increased catalase by 14% and TRAP by 168% (P<0.001, respectively) but GPx activity was not significantly different from the ethanol group. These results illustrate the significant antioxidant activity of A. douglasiana extract in‐vivo and in‐vitro.

Gastroprotective effects and antimicrobial activity of Lithraea molleoides and isolated compounds against Helicobacter pylori.

ETHNOPHARMACOLOGICAL RELEVANCE Lithraea molleoides (Vell.) Engl. (Anacardiaceae) is a medicinal plant traditionally used in South America to treat various ailments, including diseases of the digestive system. AIM OF THE STUDY To evaluate the in vivo antiulcer and antimicrobial activities against Helicobacter pylori of L. molleoides and its isolated compounds. MATERIALS AND METHODS Methanolic extract 250 and 500 mg/kg, (LmE 250 and LmE 500, respectively) and infusions, 10 g and 20 g en 100mL (LmI 10 and LmI 20, respectively) of L. molleoides was evaluated for antiulcer activity against 0.6N HCl, 0.2N NaOH, 200mg/kg acetilsalicilic acid and absolute ethanol-induced gastric ulcers in rats. The degree of erosion in the glandular part of the stomach was assessed from a scoring system. Acute toxicity in mice was also evaluated. The antiulcer effect of the isolated compounds (catechol, mannitol, rutin, gallic acid, ferulic acid and caffeic acid, 100mg/kg) was evaluated against absolute ethanol-induced gastric ulcers in rats. The anti-Helicobacter pylori activity of L. molleoides and isolated compounds was performed using broth dilution methods. RESULTS The LmE 250, LmE 500, LmI 10 and LmI 20 produced significant inhibition on the ulcer index in 0.6N HCl, 0.2N NaOH, 200mg/kg acetilsalicilic acid and absolute ethanol- induced gastric ulcers in rats. The isolated compounds, catechol, mannitol, rutin, ferulic acid and caffeic acid were active in absolute ethanol- induced gastric ulcers in rats. L. molleoides and different compounds showed antimicrobial activity in all strains tested. The lowest MIC value (0. 5 μg/mL) was obtained with catechol in six of eleven strains assayed. No signs of toxicity were observed with doses up to 2g/kg in an acute toxicity assay. CONCLUSION These findings indicate that L. molleoides displays potential antiulcerogenic and antimicrobial activities and the identification of active principles could support the use of this plant for the treatment of digestive affections.

Effect of dehydroleucodine on intestinal transit: structural basis of the interaction with the α(2)-adrenergic receptor.

The activity of dehydroleucodine, a sesquiterpene lactone obtained from Artemisia douglasiana, was studied in mice small intestinal transit. Its mechanism was evaluated in the presence of several adrenergic and cholinergic antagonist drugs and one opioid antagonist. Docking of dehydroleucodine into the homology model of the α2-adrenergic receptor allowed us to analyze the structural basis of their interactions. The experiments showed that dehydroleucodine delayed intestinal transit. The docking of dehydroleucodine showed a unique binding site, equivalent to the binding site of carozolol in the β-adrenergic receptor. The results suggested that dehydroleucodine produced an inhibitory effect on intestinal transit. Its action could be mediated, at least in part, through the α2-adrenergic receptor.

Diuretic activity of aqueous extract and betulin from Colliguaja integerrima in rats.

Five known compounds were isolated from the aerial parts of Colliguaja integerrima Gillies & Hook (Euphorbiaceae). A pharmacological evaluation of the diuretic activity of the plant was carried out in isotonic saline-loaded rats. The data reported in the present work indicate that the aqueous extract of the aerial parts from C. integerrima showed a moderate diuretic activity. The urinary levels of sodium and potassium are increased by treatment with C. integerima aqueous extract. This activity could be due, in part, to the presence of betulin isolated as the major metabolite of C. integerrima.

Intrarectal Dehydroleucodine Suppresses Trinitrobenzene Sulfonic Acid–Induced Colitis in Rats, A Model for Inflammatory Bowel Disease

Abstract Dehydroleucodine (DhL), isolated from Artemisia douglasiana. Besser (Asteraceae), prevents damage in acetic acid–induced colitis in rats. The trinitrobenzene sulfonic acid (TNBS)-induced model of chronic inflammation of the rat colon was used to determine the efficacy of DhL, at dose of 40 mg/kg, administered in enema form. All rats were sacrificed on day 7 and the colon excised, weighed, and rated macroscopically. Sections of colon were processed for light microscopy. Macroscopic scoring showed a decrease (p < 0.001) in the degree of damage in the DhL group compared with the group of rats treated with TNBS. Colon mass decreased (p < 0.05) in the DhL group compared with the TNBS group. Treatment with DhL resulted in a reduction in the incidence of diarrhea. Light-microscopic examination revealed preservation of mucosal architecture in the DhL-treated rats. DhL had an effective healing capacity at both macroscopic and microscopic levels. We conclude that DhL decreases injury and/or promotes healing in this model.

Cytoprotective Activity of Minor Constituents of Artemisia Douglasiana

Abstract 3α-Hydroxycarvotagenone and its epimer 3β-hydroxy carvotagenone were isolated as a minor mixture and its structure determined by spectral means. The mixture was then used in cytoprotection experiments. The mixture, in spite of possessing a Michael acceptor, did not show cytoprotective activity. The lack of activity was attributed to the presence of a -OH group next to the β-carbon of the Michael acceptor. This -OH group could react in a intramolecular way yielding an epoxide which would produce the inhibition of the Michael acceptor. In order to confirm this, the mixture was acetylated and the mixture of acetates used in our cytoprotection experiments. The mixture of acetates showed a moderate but significant cytoprotection probing the existence of some kind of stereoelectronic interaction between the acceptor and the nucleophile.

Antinociceptive effect of neo-clerodane diterpenes obtained from Baccharis flabellata

We report here for the first time antinociceptive effects of extracts from Baccharis flabellata. Two extracts in this analysis, one obtained in summer and the other during winter time. Our results indicate that both extract show strong antinociceptive effects, being the extracts obtained during the summer significantly more active. Our results suggest that this activity is mainly due to the presence of the diene-acid clerodane ent-15,16-epoxy-19-hydroxy-1,3,13(16),14-clerodatetraen-18-oic acid (DAC) and its dimer called DACD. Employing naloxone as an antagonist of opioid receptors, we demonstrated that both compounds act on opioid receptors, being the antinociceptive effect of DACD stronger than DAC. Thus, the antinociceptive activity of DACD was almost two times stronger than DAC (44.8 over 24.6 s in the hot-plate test) after one hour of treatments. In order to better understand the mechanism of action at molecular level of these compounds, we conducted a molecular modeling study analyzing the molecular interactions of DAC and DACD complexes with the κ-ORs. Our results suggest interactions for both DAC and DACD with Gln115, Val118, Tyr119, Asn122 and Tyr313 stabilizing their complexes; however, these interactions are significantly stronger for DACD with respect to DAC. This finding could explain why DACD have a higher affinity for the κ-ORs. These results are in agreement with the obtained antinociceptive effect. In addition, our results indicate that these neoclerodanes would have a mechanism of action similar to that of salvinorin A; such information can be very useful for the design of new inhibitors of κ-ORs.