Association study between ceftriaxone and a synthetic amide against strains of Pseudomonas aeruginosa

Pseudomonas aeruginosa is a non-lactose fermenting Gram-negative bacteria responsible for causing numerous nosocomial infections. The present research aimed to analyze the anti-Pseudomonas aeruginosa potential of 2-Chloro-N-(4-fluoro-3-nitrophenyl)acetamide (A8). The antibacterial potential of A8 was evaluated from the Minimum Inhibitory Concentration (MIC), Minimum Bactericidal Concentration (MBC) and Association using the checkerboard method. MIC and MBC values were 512 µg/mL for all P. aeruginosa strains evaluated, demonstrating predominantly bactericidal activity. Furthermore, when A8 was associated with the drug ceftriaxone, pharmacological additivity and indifference were evidenced. In this sense, the synthetic amide was interesting, since it demonstrates the potential to become a possible candidate for an antimicrobial drug.

Antifungal activity of 2-chloro-N-phenylacetamide: a new molecule with fungicidal and antibiofilm activity against fluconazole-resistant Candida spp

In the current context of emerging drug-resistant fungal pathogens such as Candida albicans and Candida parapsilosis, discovery of new antifungal agents is an urgent matter. This research aimed to evaluate the antifungal potential of 2-chloro-N-phenylacetamide against fluconazole-resistant clinical strains of C. albicans and C. parapsilosis. The antifungal activity of 2-chloro-N-phenylacetamide was evaluated in vitro by the determination of the minimum inhibitory concentration (MIC), minimum fungicidal concentration (MFC), inhibition of biofilm formation and its rupture, sorbitol and ergosterol assays, and association between this molecule and common antifungal drugs, amphotericin B and fluconazole. The test product inhibited all strains of C. albicans and C. parapsilosis, with a MIC ranging from 128 to 256 µg.mL-1, and a MFC of 512-1,024 µg.mL-1. It also inhibited up to 92% of biofilm formation and rupture of up to 87% of preformed biofilm. 2-chloro-N-phenylacetamide did not promote antifungal activity through binding to cellular membrane ergosterol nor it damages the fungal cell wall. Antagonism was observed when combining this substance with amphotericin B and fluconazole. The substance exhibited significant antifungal activity by inhibiting both planktonic cells and biofilm of fluconazole-resistant strains. Its combination with other antifungals should be avoided and its mechanism of action remains to be established.

Cardiovascular characterization of the novel organic mononitrate NDIBP in rats

Organic nitrates are widely used to restore endogenous nitric oxide (NO) levels reduced by endothelial nitric oxide synthase dysfunction. However, these drugs are associated with undesirable side effects, including tolerance. This study aims to investigate the cardiovascular effects of the new organic nitrate 1,3-diisobutoxypropan-2-yl nitrate (NDIBP). Specifically, we assessed its effects on blood pressure, vascular reactivity, acute toxicity, and the ability to induce tolerance. In vitro and ex vivo techniques showed that NDIBP released NO both in a cell-free system and in isolated mesenteric arteries preparations through a process catalyzed by xanthine oxidoreductase. NDIBP also evoked endothelium-independent vasorelaxation, which was significantly attenuated by 2-phenyl-4,4,5,5,-tetramethylimidazoline-1-oxyl 3-oxide (PTIO, 300 μM), a nitric oxide scavenger; 1-H-[1,2,4] oxadiazolo-[4,3-a]quinoxalin-1-one (ODQ, 10 μM), a soluble guanylyl cyclase inhibitor; tetraethylammonium (TEA, 3 mM), a potassium channel blocker; febuxostat (500 nM), a xanthine oxidase inhibitor; and proadifen (10 μM), an inhibitor of cytochrome P450 enzyme. Furthermore, this organic nitrate did not induce tolerance in isolated vessels and presented low toxicity following acute oral administration. In vivo changes on cardiovascular parameters were assessed using normotensive and renovascular hypertensive rats. NDIBP evoked a reduction of blood pressure that was significantly higher in hypertensive animals. Our results suggest that NDIBP acts as a NO donor, inducing blood pressure reduction without having the undesirable effects of tolerance. Those effects seem to be mediated by activation of NO-sGC-cGMP pathway and positive modulation of K+ channels in vascular smooth muscle.

Synthesis of New Cyclic Imides Derived from Safrole, Structure- and Ligand-based Approaches to Evaluate Potential New Multitarget Agents Against Species of Leishmania

BACKGROUND

Leishmaniasis is a neglected disease that does not have adequate treatment. It affects around 12 million people around the world and is classified as a neglected disease by the World Health Organization. In this context, strategies to obtain new, more active and less toxic drugs should be stimulated. Sources of natural products combined with synthetic and chemoinformatic methodologies are strategies used to obtain molecules that are most likely to be effective against a specific disease. Computer-Aided Drug Design has become an indispensable tool in the pharmaceutical industry and academia in recent years and has been employed during various stages of the drug design process.

OBJECTIVES

Perform structure- and ligand-based approaches, synthesize and characterize some compounds with materials available in our laboratories to verify the method's efficiency.

METHODS

We created a database with 33 cyclic imides and evaluated their potential anti- Leishmanial activity (L. amazonensis and L. donovani) through ligand- and structure-based virtual screening. A diverse set selected from ChEMBL databanks of 818 structures (L. donovani) and 722 structures (L. amazonensis), with tested anti-Leishmanial activity against promastigotes forms, were classified according to pIC50 values to generate and validate a Random Forest model that shows higher statistical indices values. The structures of four different L. donovani enzymes were downloaded from the Protein Data Bank and the imides' structures were submitted to molecular docking. So, with available materials and technical feasibility of our laboratories, we have synthesized and characterized seven compounds through cyclization reactions between isosafrole and maleic anhydride followed by treatment with different amines to obtain new cyclic imides to evaluate their anti-Leishmanial activity.

RESULTS

In silico study allowed us to suggest that the cyclic imides 516, 25, 31, 24, 32, 2, 3, 22 can be tested as potential multitarget molecules for leishmanial treatment, presenting activity probability against four strategic enzymes (Topoisomerase I, N-myristoyltransferase, cyclophilin and Oacetylserine sulfhydrylase). The compounds synthesized and tested presented pIC50 values less than 4.7 for Leishmania amazonensis.

CONCLUSION

After combined approach evaluation, we have synthesized and characterized seven cyclic imides by IR, 1H NMR, 13C-APT NMR, COSY, HETCOR and HMBC. The compounds tested against promastigote forms of L. amazonensis presented pIC50 values less than 4.7, showing that our method was efficient in predicting true negative molecules.

Synthesis and characterization of a novel organic nitrate NDHP: Role of xanthine oxidoreductase-mediated nitric oxide formation

In this report, we describe the synthesis and characterization of 1,3-bis(hexyloxy)propan-2-yl nitrate (NDHP), a novel organic mono nitrate. Using purified xanthine oxidoreductase (XOR), chemiluminescence and electron paramagnetic resonance (EPR) spectroscopy, we found that XOR catalyzes nitric oxide (NO) generation from NDHP under anaerobic conditions, and that thiols are not involved or required in this process. Further mechanistic studies revealed that NDHP could be reduced to NO at both the FAD and the molybdenum sites of XOR, but that the FAD site required an unoccupied molybdenum site. Conversely, the molybdenum site was able to reduce NDHP independently of an active FAD site. Moreover, using isolated vessels in a myograph, we demonstrate that NDHP dilates pre-constricted mesenteric arteries from rats and mice. These effects were diminished when XOR was blocked using the selective inhibitor febuxostat. Finally, we demonstrate that NDHP, in contrast to glyceryl trinitrate (GTN), is not subject to development of tolerance in isolated mesenteric arteries.

Nitric oxide generation by the organic nitrate NDBP attenuates oxidative stress and angiotensin II-mediated hypertension

BACKGROUND AND PURPOSE

NO deficiency and oxidative stress are crucially involved in the development or progression of cardiovascular disease, including hypertension and stroke. We have previously demonstrated that acute treatment with the newly discovered organic nitrate, 2-nitrate-1,3-dibuthoxypropan (NDBP), is associated with NO-like effects in the vasculature. This study aimed to further characterize the mechanism(s) and to elucidate the therapeutic potential in a model of hypertension and oxidative stress.

EXPERIMENTAL APPROACH

A combination of ex vivo, in vitro and in vivo approaches was used to assess the effects of NDBP on vascular reactivity, NO release, NADPH oxidase activity and in a model of hypertension.

KEY RESULTS

Ex vivo vascular studies demonstrated NDBP-mediated vasorelaxation in mesenteric resistance arteries, which was devoid of tolerance. In vitro studies using liver and kidney homogenates revealed dose-dependent and sustained NO generation by NDBP, which was attenuated by the xanthine oxidase inhibitor febuxostat. In addition, NDBP reduced NADPH oxidase activity in the liver and prevented angiotensin II-induced activation of NADPH oxidase in the kidney. In vivo studies showed that NDBP halted the progression of hypertension in mice with chronic angiotensin II infusion. This was associated with attenuated cardiac hypertrophy, and reduced NADPH oxidase-derived oxidative stress and fibrosis in the kidney and heart.

CONCLUSION AND IMPLICATIONS

The novel organic nitrate NDBP halts the progression of angiotensin II-mediated hypertension. Mechanistically, our findings suggest that NDBP treatment is associated with sustained NO release and attenuated activity of NADPH oxidase, which to some extent requires functional xanthine oxidase.

The new nitric oxide donor cyclohexane nitrate induces vasorelaxation, hypotension, and antihypertensive effects via NO/cGMP/PKG pathway

We investigated the cardiovascular effects induced by the nitric oxide donor Cyclohexane Nitrate (HEX). Vasodilatation, NO release and the effects of acute or sub-chronic treatment with HEX on cardiovascular parameters were evaluated. HEX induced endothelium-independent vasodilatation (Maximum effect [efficacy, ME] = 100.4 ± 4.1%; potency [pD2] = 5.1 ± 0.1). Relaxation was attenuated by scavenging nitric oxide (ME = 44.9 ± 9.4% vs. 100.4 ± 4.1%) or by inhibiting the soluble guanylyl cyclase (ME = 38.5 ± 9.7% vs. 100.4 ± 4.1%). In addition, pD2 was decreased after non-selective blockade of K⁺ channels (pD2 = 3.6 ± 0.1 vs. 5.1 ± 0.1) or by inhibiting K_ATP channels (pD2 = 4.3 ± 0.1 vs. 5.1 ± 0.1). HEX increased NO levels in mesenteric arteries (33.2 ± 2.3 vs. 10.7 ± 0.2 au, p < 0.0001). Intravenous acute administration of HEX (1–20 mg/kg) induced hypotension and bradycardia in normotensive and hypertensive rats. Furthermore, starting at 6 weeks after the induction of 2K1C hypertension, oral treatment with the HEX (10 mg/Kg/day) for 7 days reduced blood pressure in hypertensive animals (134 ± 6 vs. 170 ± 4 mmHg, respectively). Our data demonstrate that HEX is a NO donor able to produce vasodilatation via NO/cGMP/PKG pathway and activation of the ATP-sensitive K⁺ channels. Furthermore, HEX acutely reduces blood pressure and heart rate as well as produces antihypertensive effect in renovascular hypertensive rats.

2-(5-Methyl-1,3,4-oxa-diazol-2-yl)phenyl acetate

In the title compound, C₁₁H₁₀N₂O₃, which is a potential bioactive compound, the benzene and oxa­diazole rings are approximately coplanar, with an inter-ring dihedral angle of 4.14 (2)°, while the ester plane is rotated out of the benzene plane [dihedral angle = 82.69 (9)°]. In the crystal, the mol­ecules form layers down the a axis with weak π–π inter­actions between the oxa­diazole and benzene rings [minimum ring centroid separation = 3.7706 (14) Å].

The new nitric oxide donor 2-nitrate-1,3-dibuthoxypropan alters autonomic function in spontaneously hypertensive rats

Previously, we found that the nitrate synthesized from glycerin, 2-nitrate-1,3-dibuthoxypropan (NDBP), increased NO levels in rat aortic smooth muscle cells, inducing vasorelaxation in mesenteric artery. However, its effects on blood pressure and heart rate as well as on autonomic function were not investigated. This study evaluated the action of NDBP on these cardiovascular parameters in spontaneously hypertensive (SHR) and Wistar Kyoto (WKY) rats. We found that NDBP causes a biphasic response: hypotension and bradycardia followed by hypertension and tachycardia in WKY and SHR rats. Atropine (2mg/kg) blunted the hypotension induced by NDBP (15 mg/kg) in WKY and SHR (-75 ± 9 vs -12 ± 3 mmHg, n=6; -101 ± 6 vs -7 ± 2 bpm, n=6; respectively, p<0.05) and the pressor response to the compound was potentiated. Furthermore, vagotomy reduced the bradycardia in WKY and SHR (-136 ± 8 vs -17 ± 2, n=4, p<0.05; -141 ± 9 vs -8 ± 2, n=6, p<0.05). Moreover, hexamethonium (30 mg/kg) reduced both bradycardia (-278 ± 23 vs -48 ± 3 in WKY; -285 ± 16 vs -27 ± 19 in SHR, n=4; p<0.05) and pressor response (28 ± 8 vs -9 ± 5-WKY, n=6; 42 ± 7 vs -19 ± 8-SHR, n=5; p<0.05). In addition, administration of methylene blue (4 mg/kg) attenuated the hypotensive and bradycardic responses to the NDBP in all groups. In conclusion, NDBP induces bradycardia by direct vagal stimulation and pressor response by increasing sympathetic outflow to the periphery.