Jim Iley

Metabolism of primaquine by liver homogenate fractions. Evidence for monoamine oxidase and cytochrome P450 involvement in the oxidative deamination of primaquine to carboxyprimaquine.

The role of monoamine oxidase (MAO) and cytochrome P450 (P450) in the oxidative deamination of primaquine by rat liver fractions was studied. Rat liver fractions including liver homogenate, mitochondria, microsomes and 100,000 g supematant fractions were prepared from a pool of rat livers and characterised using benzylamine as a probe for MAO activity and N,N-dimethylbenzamide as a probe for P450 N-dealkylation activity. Incubation of all fractions with primaquine yielded carboxyprimaquine as the only metabolite detectable by HPLC. The mitochondrial fraction, which contained MAO activity but not P450 activity, presented the highest Vmax/K(M) value for the formation of carboxyprimaquine (8.5 x 10(-6) dm3mg(-1)h(-1). A substantially lower Vmax/K(M) value (1.3 x 10(-6) dm3mg(-1)h(-1)) was obtained in the microsomal fraction, which contained P450 but not MAO activity. The liver homogenate fraction presented a similar value (1.8 x 10(-6) dm3mg(-1)h(-1), though it contained both enzyme systems. Incubations of all the fractions that presented MAO activity, in presence of the MAO inhibitor pargiline, resulted in a marked inhibition of primaquine oxidation. P450 inhibitor SKF 525-A effectively inhibited primaquine metabolism in the microsomal fraction but inhibition in the liver homogenate was less effective. The results are consistent with an important role for MAO in primaquine biotransformation, though clearly metabolism by P450 has a contribution role.

Reaction of naphthoquinones with substituted nitromethanes. Facile synthesis and antifungal activity of naphtho[2,3-d]isoxazole-4,9-diones.

We report here a simple entry into naphtho[2,3-d]isoxazole-4,9-dione system containing a EWG in position 3 using the readily available 2,3-dichloro-1,4-naphthoquinone and nitromethyl derivatives in the presence of base. Antifungal activity of synthesised naphthoquinones was evaluated against ATCC and PYCC reference strains of Candida. The results suggest that the naphtho[2,3-d]isoxazole-4,9-dione scaffold has the potential to be developed into novel and safe therapeutic antifungal agents.

Design, Synthesis and Stability of N-Acyloxymethyl- and N-Aminocarbonyloxymethyl-2-azetidinones as Human Leukocyte Elastase Inhibitors

A series of N-acyloxymethyl- and N-aminocarbonyloxymethyl derivatives of 2-azetidinones, 3, with different substituent patterns at the beta-lactam C-3 and C-4 positions, were designed as potential mechanism-based inhibitors for human leukocyte elastase and found to exhibit inhibitory potency and selectivity for the enzyme.

Dipeptide derivatives of primaquine as transmission-blocking antimalarials : Effect of aliphatic side-chain acylation on the gametocytocidal activity and on the formation of carboxyprimaquine in rat liver homogenates

AbstractPurpose. Dipeptide derivatives of primaquine (PQ) with reduced oxidative deamination to the inactive metabolite carboxypnmaquine were synthesized and evaluated as a novel class of transmission-blocking antimalarials. Methods. Antimalarial activity was studied using a model consisting of mefloquine-resistant Plasmodium berghei ANKA 25R/10, Balb C mice, and Anopheles stephensi mosquitoes. Metabolic studies were performed with rat liver homogenates, and the incubates were analyzed by HPLC. Results. All dipeptide derivatives and glycyl-PQ completely inhibited the appearance of oocysts in the midguts of the mosquitoes at 15 mg/ kg, while N-acetylprimaquine was not active at this dose. However, none of the title compounds were able to block oocyst production at 3.75 mg/kg, in contrast with primaquine. Exception for sarc-gly-PQ, all remaining compounds prevented sporozoite formation in the salivary glands of mosquitoes at a dose of 3.75 mg/kg. Simultaneous hydrolysis to primaquine and gly-PQ ocurred with the following order of Vmax/ Km: for primaquine formation, L-ala-gly-PQ > L-phe-gly-PQ > gly-gly-PQ; and for gly-PQ formation, L-phe-gly-PQ > L-ala-gly-PQ > gly-gly-PQ. In contrast, primaquine was not released from D-phe-gly-PQ, sarc-gly-PQ, and N-acetylprimaquine. Neither carboxyprimaquine nor 8-amino- 6-methoxy- quinoline were detected in any of the incubation mixtures. Conclusions. The title compounds prevent the development of the sporogonic cycle of Plasmodium berghei. Gametocytocidal activity is independent of the rate and pathway of primaquine formation. Acylation of the aliphatic side-chain effectively prevents the formation of Carboxyprimaquine, but the presence of a terminal amino group appears to be essential for the gametocytocidal activity.

Rational design, synthesis, biophysical and antiproliferative evaluation of fluorenone derivatives with DNA G-quadruplex binding properties.

Molecular modeling studies carried out with experimental DNA models with the sequence d[AG3(T2AG3)3] suggest that the introduction of a net positive charge onto the side chain of a series of fluorenone carboxamides can improve G‐quadruplex binding. The terminal morpholino moiety was replaced with a novel N‐methylmorpholinium cation starting from two 4‐carboxamide compounds. A different substitution on the fluorenone ring was also investigated and submitted to the same quaternarization process. All compounds were analyzed for their DNA binding properties by competition dialysis methods. In vitro antiproliferative tests were carried out against two different tumor cell lines. Docking experiments were conducted by including all four known human repeat unit G‐quadruplex DNA sequences (27 experimentally determined conformations) against the most active fluorenone derivatives. The results of theoretical, biophysical, and in vitro experiments indicate two novel derivatives as lead compounds for the development of a new generation of G‐quadruplex ligands with greater potency and selectivity.

Acyloxymethyl as a drug protecting group: Part 4. The hydrolysis of tertiary amidomethyl ester prodrugs of carboxylic acid agents.

AbstractPurpose. Novel tertiary amidomethyl esters were synthesized and evaluated as potential prodrugs of carboxylic acid agents. Methods. The hydrolyses of the title compounds in buffer solutions and in plasma were studied by UV spectroscopy and HPLC. Results. Amidomethyl esters were hydrolyzed by acid-catalyzed, base-catalyzed and pH-independent pathways. Both the acid-catalyzed,

The microsomal demethylation of N,N-dimethylbenzamides: Substituent and kinetic deuterium isotope effects

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Inactivation of rat liver cytochrome P450 (P450) by N,N-dimethylformamide and N,N-dimethylacetamide

, and pH-independent processes, ko, were strongly affected by the electronic and steric nature of the N-substituent in the pro-moiety. For both processes, the electronic effect exerted greater influence, and electron-withdrawing substituents retarded reaction. The pH-independent hydrolysis of amidomethyl esters were dependent on the pKa of the carboxylate leaving group, giving a Brönsted βlg value of −0.91. The base-catalyzed,