Nitric oxide-dependent vasorelaxation induced by extractive solutions and fractions of Maytenus ilicifolia Mart ex Reissek (Celastraceae) leaves

Novel potent vasodilating agents: Evaluation of the activity and potency of LINS01005 and derivatives in rat aorta

Cardiovascular diseases (CVDs) present high prevalence rates in the current world. It is estimated that approximately one-third of the global deaths are related to CVDs, and thus there is still a need for novel drugs to treat these disorders. We serendipitously discovered that LINS01005 (5a) is a potent vasodilating agent in rat aorta, and therefore a set of analogues were evaluated for the vasodilating potency in Wistar and SHR rat thoracic aorta precontracted with norepinephrine, with endothelium intact (E+) or denuded (E-) aortic rings. Compounds 5a and 5b were the most potent, showing submicromolar potency for endothelium intact vessels (EC₅₀ 853 and 941 nM, respectively) and micromolar values for E- vessels (EC₅₀ 2.4 and 7.1 µM, respectively). These compounds were indeed significantly more potent vasodilating agents in SHR-derived aortic rings (p < 0.001), showing nanomolar potency for 5a [EC₅₀ 2.4 nM (E+) 9.0 nM (E-)] and 5b [EC₅₀ 20 nM (E+) 2.1 µM (E-)]. SAR analysis though PCA and HCA were performed, suggesting that N-phenylpiperazine is essential to the activity, while increasing volume in the substituted aromatic moiety is detrimental to the potency. This is the first report of the vasodilating properties of such compounds, and studies regarding the mechanism of action are in progress in our group.

Role of prostaglandin/cAMP pathway in the diuretic and hypotensive effects of purified fraction of Maytenus ilicifolia Mart ex Reissek (Celastraceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Although Maytenus ilicifolia is used in Brazilian folk medicine as a diuretic drug, no study has been conducted to this date in order to evaluate this ethnopharmacological statement. So, the aim of this study was to evaluate possible mechanisms involved in acute diuretic activity of the ethanolic supernatant of the infusion (SEI) obtained from Maytenus ilicifolia and to assess its relationship with a hypotensive activity by a bioassay-guided fractionation using normotensive Wistar rats.

MATERIAL AND METHODS

The preparation obtained from the infusion (SEI) and their respective fractions (Fr·H2O and Fr·EtOAc) were orally administered in a single dose to rats. The urine excretion rate, pH, density, conductivity and content of Na(+), K(+), Cl(-) and HCO3(-) were measured in the urine of saline-loaded animals. Samples of the concentration of electrolytes, urea, creatinine, aldosterone, vasopressin and angiotensin converting enzyme (ACE) activity were evaluated in collected serum. The hypotensive activity and the involvement of nitric oxide, bradykinin and prostaglandin/cAMP pathway in the hypotensive and diuretic effects were also determined.

RESULTS

Water and Na(+) excretion rate were significantly increased by Fr·EtOAc and the arterial pressure was significantly reduced, while the urinary excretion of potassium and chloride were reduced. Pre-treatment with indomethacin or DDA (2',5'-dideoxyadenosine) significantly reduced the hypotensive and diuretic activity observed. All other parameters evaluated were not affected by any treatment.

CONCLUSION

The present study reveals that Fr·EtOAc obtained from Maytenus ilicifolia may present compounds responsible for diuretic and hypotensive activities, and this effect, could involve the prostaglandin/cAMP pathway.

Inhibitory effects of Diospyros kaki in a model of allergic inflammation: role of cAMP, calcium and nuclear factor-κB

Diospyros kaki (D. kaki) has been cultivated throughout Eastern Asia for hundreds of years. D. kaki contains various biological active compounds, such as amino acids, carotenoids, flavonoids, tannins, catechins and vitamin A. Previous studies have shown that D. kaki has beneficial effects on homeostasis, constipation, hypertension, atherosclerosis and allergic dermatitis and is a good source of antioxidants, polyphenols and dietary fiber. However, the anti-allergic and anti-inflammatory effects of D. kaki have not yet been elucidated. This study aimed to investigate the protective effects of the aqueous extract of Diospyros kaki (AEDK) on mast cell-mediated allergic inflammation and to determine its possible mechanisms of action by using in vitro and in vivo mast cell-based models. The cAMP and intracellular calcium levels were measured to clarify the mechanisms by which AEDK inhibits the release of histamine from mast cells. AEDK inhibited the release of histamine and β-hexosaminidase from mast cells by modulating cAMP and intracellular calcium levels. We also measured the expression of pro-inflammatory cytokines, such as tumor necrosis factor (TNF)-α and interleukin (IL)-1β. AEDK decreased gene expression and the secretion of the pro-inflammatory cytokines, TNF-α and IL-1β by inhibiting nuclear factor-κB. In addition, AEDK inhibited systemic and cutaneous allergic reaction. The inhibitory effects of AEDK on allergic reaction and the release of histamine were found to be similar to those of disodium cromoglycate, a known anti-allergic drug. To isolate the active component of AEDK, activity-guided fractionation was performed, based on the inhibitory effects on systemic anaphylaxis. Catechin was identified as an active compound. The present findings provide evidence that AEDK inhibits allergic inflammation and suggest the therapeutic application of AEDK in allergic inflammatory disorders.

Maytenus ilicifolia dry extract protects normal cells, induces apoptosis and regulates Bcl-2 in human cancer cells

Maytenus is the largest genus of the family Celastraceae and the species Maytenus ilicifolia (popularly known as ‘Espinheira Santa’). It is widely used in traditional Brazilian medicine to treat stomach conditions including nausea, gastritis, and ulcers. In this study, the apoptotic effects of a spray-dried extract of M. ilicifolia (SDEMI) was evaluated using human hepatocellular cells (HepG2), colorectal carcinoma cells (HT-29), and normal keratinocytes (HaCaT). Cells were treated with SDEMI for 4 and 24 h, then were assayed for levels of apoptosis, caspase-3, and Bcl-2 by flow cytometry, immunostaining, and Western blot, respectively. Significant differences between groups were determined using analysis of variance ( P < 0.05). For HepG2 and HT-29 cells treated with SDEMI, various cytotoxic effects were observed compared with control cells at all timepoints assayed ( P < 0.001). Furthermore, positive caspase-3 staining and down-regulation of Bcl-2 were observed, consistent with the induction of cell death detected in these cell lines. In contrast, treatment of HaCaT cells with SDEMI was associated with a protective effect compared with control cells at both timepoints ( P < 0.001). For example, increased expression of Bcl-2 and negative caspase-3 staining were detected. Taken together, these results suggest that SDEMI protects normal cells, while SDEMI mediates induction of apoptosis via down-regulation of Bcl-2 and involvement of caspase-3 in human carcinoma cells.

Antiprotozoal sesquiterpene pyridine alkaloids from Maytenus ilicifolia

As part of a bioprospecting program aimed at the discovery of antiprotozoal agents from the Brazilian flora, two new sesquiterpene pyridine alkaloids, ilicifoliunines A (1) and B (2), along with the known alkaloids aquifoliunine E-I (3) and mayteine (4), were isolated from the root bark of Maytenus ilicifolia. The structures of 1 and 2 were established on the basis of spectroscopic data interpretation. Alkaloid 3 displayed potent in vitro antiprotozoal activity against Leishmania chagasi and Trypanosoma cruzi, with IC(50) values of 1.4 and 41.9 μM, respectively, as well as low cytotoxicity against murine peritoneal macrophages (IC(50) of 1.8 mM).

Effects and mechanism of turmeric vasorelaxation of the thoracic aorta in hypercholesterolemic rats

An extract of Curcuma longa was tested in hypercholesterolemic rats to investigate its potential therapeutic effect on vascular conditions. Four experimental groups were used: normal diet (ND) control group, high cholesterol diet (HCD) group, and HCD subgroups supplemented with turmeric extract at 100 or 300 mg/kg of body weight (HCD100Tur and HCD300Tur groups, respectively). Turmeric extract was fed orally to animals, and dietary treatments lasted for 28 days. Hypercholesterolemia developed in the HCD, HCD100Tur, and HCD300Tur rats. Segments of the thoracic aorta were isolated, and an organ bath experiment was used to assess the vasorelaxation capability among all rats. Rats fed only HCD showed a marked decrease in acetylcholine-induced vasorelaxation compared with ND control rats. The HCD100Tur and HCD300Tur rats showed significant improvement in vasorelaxation compared with HCD rats. When vasorelaxation was induced by high concentrations of sodium nitroprusside, no differences in vasorelaxation were observed among the four groups of rats. A mechanistic study showed that HCD100Tur and HCD300Tur rats had significantly higher levels of the antioxidant enzymes superoxide dismutase and glutathione peroxidase than HCD rats. The transcript levels of heat shock protein 70 (hsp70), bcl2, bax-α, caspase (casp3), and glyceraldehyde 3-phosphate dehydrogenase in aortic tissues indicated that hypercholesterolemia significantly increased the expression of bax-α and casp3 but down-regulated bcl2 expression compared with the control group. Turmeric increased the expression of hsp70 and bcl2 but greatly reduced casp3 expression, indicating that turmeric improves vasorelaxation of the aorta in hypercholesterolemic rats by increasing antioxidant enzyme activities and likely suppressing apoptosis.

Vasorelaxant and hypotensive effects of the extract and the isolated flavonoid rutin obtained from Polygala paniculata L

Objectives

This study aimed to investigate the in-vitro and in-vivo cardiovascular effects of the crude hydroalcoholic extract from Polygala paniculata (HEPP) in rats.

Methods

The procedures were performed on aortic rings and on normotensive anaesthetized rats.

Key findings

When tested in endothelium-intact aorta rings, HEPP (30–1000 µg/ml) produced a significant non-concentration-dependent relaxing effect (∼40%), which was completely prevented by incubation with L-NAME (nitric oxide synthase inhibitor), ODQ (soluble guanylate cyclase inhibitor) and partially inhibited by tetraethylammonium (TEA; a non-selective potassium channel blocker) and charybdotoxin (a large- and intermediate-conductance calcium-activated potassium channel blocker). In contrast, atropine (a muscarinic receptor antagonist) or pyrilamine(a histamine H1 receptor antagonist) had no effect. Furthermore, oral administration of HEPP (30–300 mg/kg) in anaesthetized rats caused a dose-dependent and sustained hypotensive action. This effect was unchanged by atropine or TEA, but was strongly reduced in rats continuously infused with L-NAME or methylene blue. Moreover, rutin (1–3 mg/kg) administered by an intravenous route also caused a dose-dependent hypotensive effect in rats.

Conclusions

Our results demonstrated that the extract obtained from P. paniculata induces potent hypotensive and vasorelaxant effects that are dependent on the nitric oxide/guanylate cyclase pathway. These effects could be related, at least in part, to the rutin contents in this extract.

Muscarinic-dependent inhibition of gastric emptying and intestinal motility by fractions of Maytenus ilicifolia Mart ex. Reissek

ETHNOPHARMACOLOGICAL RELEVANCE

Maytenus ilicifolia Mart. ex. Reissek (Celastraceae) is widely used in Brazilian folk medicine to treat gastric disturbances.

AIM OF THE STUDY

This work intended to characterize the effects of Maytenus ilicifolia on gastrointestinal motility.

MATERIALS AND METHODS

Gastric emptying and intestinal transit were measured in the same animal. Mice received a semisolid marked with phenol red, half an hour after treatment with extracts. The amount of marker in the stomach and the distance reached in the intestine after 15 min were measured as index of gastrointestinal emptying and intestinal transit, respectively.

RESULTS

Intraperitoneal administration of a flavonoid-rich extract potently reduced the gastric emptying (ED(50)=89 mg/kg) and the intestinal transit (ED(50)=31 mg/kg) of mice. Bio-guided purification of the flavonoid-rich extract by chemical partition with solvents of decreasing polarity yielded fraction insF with about 12-14 times higher activity than the initial flavonoid extract in both the gastric emptying and the intestinal transit. The inhibitory effects of the insF (9.7 mg/kg, i.p.) on gastric emptying and intestinal transit were reversed by co-administration of bethanechol (10 mg/kg, s.c.) but not by co-administration of metoclopramide (30 mg/kg, p.o.) indicating muscarinic but not dopaminergic interaction of the compounds of Maytenus. Chemical investigation of the insF fraction by HPLC-MS allowed the identification of 4 free flavonoids (catechin, epicatechin, quercetin and kaempferol), 29 flavonol glycosides and 8 tannins. The flavonol glycosides ranged from 1 to 4 monosaccharide units, having mainly quercetin and kaempferol as aglycone moieties, and the tannins were composed by catechin/epicatechin and/or afzelechin/epiafzelechin.

CONCLUSIONS

Overall, the results indicate that the components of Maytenus ilicifolia have a potential use in the treatment of gastrointestinal motility disturbances such as diarrhea.

Activation of muscarinic receptors by a hydroalcoholic extract of Dicksonia sellowiana Presl. HooK (Dicksoniaceae) induces vascular relaxation and hypotension in rats

Dicksonia sellowiana (Presl.) Hook is a native plant from the Central and South Americas that contain high levels of polyphenols, antioxidant compounds involved in protection against inflammation, cancer and cardiovascular risk. A phytomedicinal preparation obtained from aerial parts of D. sellowiana is currently under clinical evaluation in Brazil against asthma, and has been associated with several other beneficial effects. This study demonstrates that a hydroalcoholic extract obtained from D. sellowiana leaves (HEDS) fully relax, in a concentration-dependent manner, rat aortic rings precontracted with phenylephrine. Moreover, administration of HEDS (10, 20 and 40 mg/kg, i.v.) in anaesthetized rats resulted in a strong but reversible hypotension. Aortic relaxation induced by HEDS was abolished by endothelium removal, by incubation of the nitric oxide synthase inhibitor L-NAME, or the soluble guanylate cyclase inhibitor ODQ. In addition, this effect was partially inhibited by indomethacin (a cyclooxygenase inhibitor) and KT 5730 (a PKA inhibitor). The potassium channels blockade by either tetraethylammonium or charybdotoxin also resulted in a potent inhibition of HEDS-induced aortic relaxation, whereas apamine only slightly reduced it. In addition HEDS-induced relaxation was unchanged by 4-amynopiridine and glibenclamide. The selective muscarinic receptor antagonist atropine counteracted both aortic relaxation and blood pressure reduction generated by HEDS. Experiments using HPLC revealed the presence of high amounts of phenolic compounds in this extract. Taken together, our results reveal that the D. sellowiana possess substances with both in vivo and in vitro activities and that the vascular effect of HEDS involves activation of muscarinic receptors, stimulation of the nitric oxide pathway and opening of calcium-activated potassium channels.

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

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

A new triterpene with antinociceptive activity fromMaytenus robusta

A new triterpene 3,15-dioxo-21alpha-hydroxy friedelane has been isolated from methanol extract of Maytenus robusta and its structure elucidated on the basis of spectral analysis. Stigmasterol, friedelin, friedelanol and 3,15-dioxo friedelane were also obtained. 3,15-dioxo-21alpha-hydroxy friedelane was analyzed against the writhing test in mice and exhibited potent dose-dependent effects with an ID50 value of 12.5 +/- 2.1 micromol kg(-1) and a maximal inhibition of 85.90%. It was about 10-fold more active than aspirin and paracetamol, used as reference drugs.

A polysaccharide from a tea (infusion) of Maytenus ilicifolia leaves with anti-ulcer protective effects

Maytenus ilicifolia is a medicinal plant used as a tea (infusion) for treatment of stomach ulcers. This tea furnished a polysaccharide after several purification steps, consisting of a freezing-thawing process, Fehling precipitation, ultrafiltration, and dialysis. It consisted of arabinose, galactose, galacturonic acid, 4-O-methylglucuronic acid, rhamnose, and glucose in a 42:41:6:5:4:2 molar ratio. Methylation analysis, controlled Smith degradation, and NMR spectroscopy indicated that it was a type II arabinogalactan containing a (1-->3)-linked beta-d-Galp main chain, substituted at O-6 by (1-->6)-linked beta-d-Galp chains, which were mainly substituted at O-3 by (1-->5)- and (1-->3)-linked alpha-l-Araf chains, and nonreducing end-units of alpha-l-Araf and 4-O-Me-GlcpA. This polysaccharide significantly inhibited ethanol-induced gastric lesions in rats with an ED(50) of 9.3 mg/kg, suggesting that the arabinogalactan liberated from the infusion has a protective anti-ulcer effect.