A series of multifunctional codrugs (1-4), obtained by joining L-Dopa (LD) and dopamine (DA) with (R)-alpha-lipoic acid (LA), was synthesized and evaluated as potential codrugs with antioxidant and iron-chelating properties. These multifunctional molecules were synthesized to overcome the pro-oxidant effect associated with LD therapy. The physicochemical properties, together with the chemical and enzymatic stabilities of synthesized compounds, were evaluated in order to determine both their stability in aqueous medium and their sensitivity in undergoing enzymatic cleavage by rat and human plasma to regenerate the original drugs. The new compounds were tested for their radical scavenging activities, using a test involving the Fe (II)-H2O2-induced degradation of deoxyribose, and to evaluate peripheral markers of oxidative stress such as plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx) in the plasma. Furthermore, we showed the central effects of compounds 1 and 2 on spontaneous locomotor activity of rats in comparison with LD-treated animals. From the results obtained, compounds 1-4 appeared stable at a pH of 1.3 and in 7.4 buffered solution; in 80% human plasma they were turned into DA and LD. Codrugs 1-4 possess good lipophilicity (log P > 2 for all tested compounds). Compounds 1 and 2 seem to protect partially against the oxidative stress deriving from auto-oxidation and MAO-mediated metabolism of DA. This evidence, together with the "in vivo" dopaminergic activity and a sustained release of the parent drug in human plasma, allowed us to point out the potential advantages of using 1 and 2 rather than LD in treating pathologies such as Parkinson's disease, characterized by an evident decrease of DA concentration in the brain.
Aminoethylcysteine, lanthionine, cystathionine and cystine are mono-deaminated either by L-amino-acid oxidase or by a transaminase exhibiting the properties described for glutamine transaminase. The deaminated products cyclize producing the respective ketimines. Authentic samples of each ketimine were prepared by reacting the appropriate aminothiol compound with bromopyruvate, except cystine ketimine which required the interaction of thiopyruvate with cystine sulfoxide. Reduction of the first three mentioned ketimines with NaBH, yields the respective derivatives with the saturated rings of thiomorpholine and hexahydrothiazepine. The same reduction is carried out enzymically by a reductase extracted from mammalian tissues. Properties of the members of this family of compounds are described. Gas chromatography followed by mass spectrometry permits the identification of most of these products. HPLC is very useful for the determination of the ketimines by taking advantage of specific absorbance at 380 nm obtained by prior derivatization with phenylisothiocyanate. Adaptation of these and other analytical procedures to biological samples disclosed the presence of most of these compounds in bovine brain and in human urine. By using [35S]lanthionine ketimine as a representative member of the ketimine group, the specific, high-affinity, saturable and reversible binding to bovine brain membranes has been demonstrated. The binding is removed by aminoethylcysteine ketimine and by cystathionine ketimine indicating the occurrence in bovine brain of a common binding site for ketimines. The reduced ketimines are totally ineffective in competing with [35S]lanthionine ketimine. Alltogether these findings are highly indicative for the existence in mammals of a novel class of endogenous sulfur-containing cyclic products provided with a possible neurochemical function to be investigated further. Chemistry of sulfur-containing ketiminesInteraction of halopyruvate (fluoropyruvate) with aminothiols was used by Avi-Dor and Mager [l] for the quantitation of cysteine and other aminothiols by exploiting the increase of absorbance in the range of 300 nm. Hermann was the first to recognize that the typical absorbance at 296 nm of these products is due to the cyclization into a ketimine ring formed by internal addition of the amino to the carbonyl group [2, 31. In an attempt to prepare the ketimine resulting from the interaction of cysteamine with bromopyruvate [S-(2-
A series of novel molecular combinations (1-4), in which L-dopa (LD) is linked covalently via an amide bond with glutathione (GSH), were synthesized and evaluated as potential anti-Parkinson agents with antioxidant properties. These conjugates were characterized by evaluating solubility, chemical and enzymatic stabilities, and apparent partition coefficient (log P). Derivatives 2 and 4 were tested for their radical scavenging activities, by use of a test involving the Fe(II)/H2O2-induced degradation of deoxyribose. In this study, the antioxidant efficacy of codrugs 1 and 3 was also assessed through the evaluation of plasmatic activities of superoxide dismutase (SOD) and glutathione peroxidase (GPx). Furthermore, the central nervous effects and rat striatal concentration of LD and dopamine (DA) have been evaluated after oral administration of codrugs 1 and 3. Tested compounds prolonged the plasma LD levels and were able to induce sustained delivery of DA in rat striatum with respect to an equimolar dose of LD. The results suggest that compounds 1 and 3 could represent useful new anti-Parkinson agents devoid of the pro-oxidant effects associated with LD therapy and potentially able to restore the GSH depletion evidenced in the substantia nigra pars compacta (SNpc) of PD patients.
We have evaluated the development of antibodies in response to donor allograft valve implant in patients who received cellularized and decellularized allografts and determined possible immunogenic epitopes considered responsible for antibodies reactivity. Serum samples from all recipients who received cellularized allografts or decellularized allografts were collected before valve replacement and at 5, 10, 30 and 90 days post-operatively and frozen until required. Tests were performed using the Luminex-based single human leukocyte antigen (HLA)-A, -B, -C and HLA-DR, -DQ antigen microsphere assay. To determine possible immunogenic epitopes, we used the HLAMatchmaker (HLAMM) software if applicable. Decellularized grafts elicited lower levels of anti-HLA class I and II antibody formation after implantation than cellularized allografts. All patients from cellularized group presented donor-specific antibodies class I and II within 3 months of observation period. In HLAMM analysis, the cellularized group had significantly higher numbers of immunogenic epitopes than decellularized group for both class I and II (p: 0.002 - cl I / p: 0.009 - cl II / p: 0.004 - cl I and II). Our findings demonstrate that the anti-HLA antibodies detected in the cellularized group were against donor HLA possible immunogenic epitopes and that in the decellularized group the anti-HLA antibodies were not against donor HLA possible immunogenic epitopes. These findings lead us to suggest that choosing sodium dodecyl sulfate decellularization process is the best alternative to decrease the immunogenicity of allograft valve transplant.
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