Antonia Sacchi

Research on heterocyclic compounds, XLI. 2-Phenylimidazo[1,2-b]pyridazine-3-acetic derivatives: synthesis and anti-inflammatory activity

Abstract The synthesis of a group of 2-phenylimidazo[1,2-b]pyridazine-3-acetic esters and acids is described. The structures of the new compounds are supported by 1 H-NMR spectra. These compounds were tested in vivo for their anti-inflammatory, analgesic and ulcerogenic activity. All new compounds showed remarkable anti-inflammatory action in the carrageenan rat paw oedema (one third of that for indomethacin) but no significant analgesic activity in the acetic acid writhing test together with negligible ulcerogenic action, and were also found to be lacking inhibitory activity on cyclooxygenase in vitro.

Research on heterocyclic compounds. XXXII. Synthesis and cyclooxygenase-independent antiinflammatory and analgesic activity of imidazo[1,2-a]pyrimidine derivatives

Abstract The synthesis of a group of imidazo[1,2-a]pyrimidine-2-carboxylic esters, acids and amides is described. The structures of the new compounds are supported by 1H- and 13C-NMR spectra. These compounds were tested in vivo for their antiinflammatory and analgesic activities as well as for their ulcerogenic action. The ester 5b, the acid 6c and the amide 7a showed antiinflammatory action in the rat paw edema ( ∼1 3 x indomethacin ), while almost all compounds displayed significant analgesic activity in the acetic acid writhing test, particularly the 5-chloro-7-methyl derivatives 5a, 6a and 7a ( ∼1 5 x indomethacin ). All new compounds were found to be lacking in inhibitory activity on cyclooxygenase in vitro.

Ionized Prodrugs of Dehydroepiandrosterone for Transdermal lontophoretic Delivery

AbstractPurpose. The aim of this work was to synthesize ionized dehydroepiandrosterone (DHEA) prodrugs with higher water solubility, useful for iontophoretic transdermal application. Methods. The synthesized derivatives were characterized and tested for sensitivity to chemical and enzymatic hydrolysis. Solid state and solution stability was also determined. Transdermal iontophoretic anodal transport in vitro was studied using excised rabbit skin. Results. Two DHEA ionized prodrugs were synthesized: PRO1, a primary amine derivative, and PRO2, a quaternary ammonium salt. The two derivatives possess higher water solubility and lower octanol/saline partition coefficients than DHEA. Prodrugs were sensitive to enzymatic hydrolysis; in particular the primary amine was hydrolyzed faster than the quaternary salt by esterase from porcine liver in vitro. Transdermal flux of the two prodrugs was slightly higher than the parent drug. In the case of passive diffusion, only DHEA was found in the receptor compartment, indicating the complete breakdown of the prodrug in the skin. Current application gave higher drug flux and a significant amount of prodrug was found in the receptor. Conclusions. The use of ionized prodrugs of DHEA can increase the flux attainable during transdermal anodal iontophoresis by up to 7 times, but they are useful for passive transport as well.

In-vitro and in-vivo evaluation of oligoethylene esters as dermal prodrugs of 18β-glycyrrhetic acid

Novel polyoxyethylene esters of 18 β‐glycyrrhetic acid (GA) were synthesized and evaluated as potential dermal prodrugs. The permeation of these prodrugs (1a‐e) was studied in‐vitro, using excised human skin membranes (SCE; stratum corneum/epidermis) mounted in Franz type cells, and in‐vivo, evaluating the ability of these compounds to inhibit methyl nicotinate (MN)‐induced skin erythema in healthy human subjects. All the esters synthesized showed a good water stability, while the enzymatic hydrolysis rate was significantly affected by the length of the polyoxyethylenic chain used as promoiety. In in‐vitro percutaneous absorption studies, only esters 1b and 1c (respectively triethylen‐ and tetraethylenglycol derivatives) showed an increased flux through SCE membranes compared with GA. Furthermore, we observed an appreciable and sustained in‐vivo topical anti‐inflammatory activity of esters 1b and 1c compared with the parent drug.

Synthesis, hydrolysis, and skin retention of amino acid esters of α-tocopherol

The aim of this work was to synthesize new pro-vitamins of alpha-tocopherol (VE) able to release another moiety such as an amino acid, in order to obtain a combined antioxidant and moisturizing effect upon topical application. The new derivatives were characterized and tested for sensitivity to chemical and enzymatic hydrolysis. Lipophilicity was estimated using Log capacity factor and skin retention was determined in vitro, using rabbit ear skin as barrier. Five molecules were synthesized using L-proline, L-serine, L-tyrosine, L-asparagine, and L-citrulline as amino acidic moiety. All pro-vitamins showed similar or lower lipophilicity than alpha-tocopheryl acetate (VEAc), taken as reference, and similar stability in aqueous solutions. All pro-vitamins showed to be sensitive to enzymatic hydrolysis. None of the pro-vitamins crossed the skin in significant amounts, whereas they accumulated into the skin, in both the dermis and the epidermis. They are more hydrophilic and more water-soluble than the currently used acetate.

Synthesis and antihypertensive action of new Imidazo[1,2-a]pyridine derivatives, non peptidic Angiotensin II receptor antagonists

The synthesis and antihypertensive activity of a group of imidazo[1,2-a]pyridine is described. New synthesized compound have been tested both in vivo and in vitro as antagonists on Angiotensin AT1 receptor, and compared to Losartan, used as reference drug. Binding assay an Angiotensin AT1 receptor were carried on as well. Compounds 6b and 6g showed a potent antihypertensive activity and an high affinity on AT1 receptor.

Corneal Cross-Linking: Evaluating the Potential for a Lower Power, Shorter Duration Treatment.

Purpose: To determine the cross-linking effect of a riboflavin ultraviolet-A (UV-A) corneal cross-linking treatment that is both shorter and has lower energy than the Dresden protocol. Methods: In a first experiment, 12 human corneas were presoaked with riboflavin and then irradiated with UV-A at 3 mW/cm2 after clearing the surface of riboflavin, with no added riboflavin during irradiation. Percent UV-A transmission through the corneas was measured at intervals up to 30 minutes. A second experiment involved 24 porcine corneas. Eight were de-epithelialized, presoaked in riboflavin for 30 minutes, and irradiated at 1.5 mW/cm2 for 10 minutes. An additional 8 were riboflavin treated and similarly irradiated, but with epithelium intact and a final 8 corneas were not treated. Young modulus was measured in all 24 corneas at the end of the experiment. Results: The first experiment showed essentially complete riboflavin oxidation after only 10 minutes. Based on these results, a shortened UV-A exposure cross-linking experiment was designed using a reduced UV-A fluence of 1.5 mW/cm2, an endothelial exposure within safety limits in humans. With this protocol Young modulus was the same in the irradiated porcine corneas but with epithelium intact as in the untreated corneas. In contrast, Young modulus increased by a factor of 1.99 in the UV-A cross-linked corneas at 1.5 mW/cm2 for 10 minutes with the epithelium removed. Conclusions: A shorter, lower energy protocol than the Dresden protocol seems to provide a significant increase in Young modulus, similar to published results with higher energy, longer exposure protocols.

Improvement of Topical Palmitoylethanolamide Anti-Inflammatory Activity by Pegylated Prodrugs.

A small library of polyethylene glycol esters of palmitoylethanolamide (PEA) was synthesized with the aim of improving the pharmacokinetic profile of the parent drug after topical administration. Synthesized prodrugs were studied for their skin accumulation, pharmacological activities, in vitro chemical stability, and in silico enzymatic hydrolysis. Prodrugs proved to be able to delay and prolong the pharmacological activity of PEA by modification of its skin accumulation profile. Pharmacokinetic improvements were particularly evident when specific structural requirements, such as flexibility and reduced molecular weight, were respected. Some of the synthesized prodrugs prolonged the pharmacological effects 5 days following topical administration, while a formulation composed by PEA and two pegylated prodrugs showed both rapid onset and long-lasting activity, suggesting the potential use of polyethylene glycol prodrugs of PEA as a suitable candidate for the treatment of skin inflammatory diseases.

4‐amino‐6‐alkyloxy‐2‐alkylthiopyrimidine derivatives as novel non‐nucleoside agonists for the adenosine A1 receptor

Three 4‐amino‐6‐alkyloxy‐2‐alkylthiopyrimidine derivatives (4–6) were investigated as potential non‐nucleoside agonists at human adenosine receptors (ARs). When tested in competition binding experiments, these compounds exhibited low micromolar affinity (Ki values comprised between 1.2 and 1.9 μm) for the A1 AR and no appreciable affinity for the A2A and A3 ARs. Evaluation of their efficacy profiles by measurement of intracellular cAMP levels revealed that 4 and 5 behave as non‐nucleoside agonists of the A1 AR with EC50 values of 0.47 and 0.87 μm, respectively. No clear concentration‐response curves could be instead obtained for 6, probably because this compound modulates one or more additional targets, thus masking the putative effects exerted by its activation of A1 AR. The three compounds were not able to modulate A2B AR‐mediated cAMP accumulation induced by the non‐selective AR agonist NECA, thus demonstrating no affinity toward this receptor.

Studies on enantioselectivity of chiral 4-acetylamino-6-alkyloxy-2-alkylthiopyrimidines acting as antagonists of the human A3 adenosine receptor

Three A3 adenosine receptor (AR) antagonists (1-3) selected from 4-acylamino-6-alkyloxy-2-alkylthiopyrimidines previously investigated by us were modified by inserting a methyl group on their ether or thioether side chains. These compounds gave us the chance to evaluate whether their higher lipophilicity, reduced conformational freedom and chirality might improve the potency towards the A3 AR. Racemic mixtures of 1-3 were resolved using chiral HPLC methods and the absolute configurations of the enantiomers were assigned by chiroptical spectroscopy and density functional theory calculations. We measured the affinity for human A1, A2A, A2B and A3 ARs of the racemic mixtures and the pure enantiomers of 1-3 by radioligand competition binding experiments. Cell-based assays of the most potent enantiomers confirmed their A3 AR antagonist profiles. Our research led to the identification of (S)-1 with high potency (0.5 nM) and selectivity as an A3 AR antagonist. Moreover we built a docking-model useful to design new pyrimidine derivatives.