Effect of cadmium and zinc ethanolamine complexes on rat brain monoamine oxidase-B activity in vitro

Monoamine oxidase-B (MAO-B) from rat brain was inhibited strongly by the prepared cadmium and zinc ethanolamine complexes obtained from their sulphate and chloride salts. The inhibition of MAO-B by these complexes was time-dependent and fully reversible after dilution and sedimentation. In vitro, the cadmium ethanolamine complexes were more potent at inhibiting MAO-B than the zinc complexes. The inhibitory effect of these complexes follow the order: TEA>DEA>MEA, due to the alkyl residues and steric effect properties. The inhibition of MAO-B by cadmium and zinc ethanolamine complexes was a noncompetitive type. The K(i) values were calculated. The influence of the complexes on the activity of MAO-B was rather evaluated. It decreased the MAO-B activity. The IC(50) values of the two potent cadmium and zinc triethanolamine complexes on MAO-B were evaluated indicating that the complexes were tightly binding, but reversible inhibitors for MAO-B. In general, these systems may be used for preventing some neurodegenerative diseases.

Inhibitory effects of ethaverine, a homologue of papaverine, on monoamine oxidase activity in mouse brain

The effects of benzylisoquinoline compounds such as ethaverine, laudanosine, and tetrahydropapaverine on monoamine oxidase (MAO, EC 1.4.3.4) activity in mouse brain were investigated. Ethaverine showed an inhibition of MAO activity in a concentration-dependent manner (57.6% inhibition at 40 microm). Papaverine also inhibited MAO activity (38.1% inhibition at 40 microM). However, laudanosine and tetrahydropapaverine did not inhibit MAO activity. The IC50 value of ethaverine for MAO was 25.5 microm. Ethaverine non-competitively inhibited MAO activity with a substrate kynuramine. The Ki value for ethaverine was 11.9 microM. In addition, ethaverine proved to preferentially inhibit type B MAO activity in a concentration-dependent manner, with an IC50 value of 32.8 microm. These results suggest that ethaverine partially contributes to the regulation of catecholamine content.

Selective inhibitors of monoamine oxidase (MAO). 5. 1-Substituted phenoxathiin inhibitors containing no nitrogen that inhibit MAO A by binding it to a hydrophobic site

It is believed that a monoamine oxidase (MAO) inhibitor specific for MAO A, which is reversibly bound to this enzyme and displaceable by tyramine, will be an antidepressant which will not cause a rise in blood pressure when tyramine-containing foods are ingested. Some linear tricyclic compounds with a larger and a smaller group forming the central ring and with a lipophilic group ortho to the larger group (here mostly the SO2 function of phenoxathiin 10,10-dioxide) are reported to have the sought properties. Potency appears to require short length and relatively small cross section for the substituent. The 1-ethyl (13), 1-vinyl (22), 1-trifluoromethyl (27), and 1-iodo (76) phenoxathiin dioxides had the best profiles. Structure-activity relationships, syntheses, and a possible rationale for the selectivity of these compounds and related tricyclics are given. Compound 13 was selected for further development. A summary of pharmacological data for 13 is given.

Characterization of in vitro metabolites from human liver microsomes using directly coupled hplc-nmr: application to a phenoxathiin monoamine oxidase-A inhibitor

1. The metabolism of 1-ethylphenoxathiin-10,10-dioxide (BW1370U87), an experimental compound designed as an inhibitor of monoamine oxidase-A for use as a possible anti-depression agent, has been studied in a human liver microsome preparation. 2. The identities of the metabolites have been determined using directly coupled hplc-1H nmr at 600 MHz in the stop-flow mode in this first study of in vitro xenobiotic metabolism using hplc-nmr. 3. The xenobiotic substances that were identified comprised the parent compound BW1370U87 (with -CH2CH3 at C1) together with sidechain-oxidized metabolites with C1 substituents of -CHOH.CH3, -CH2.CH2OH, -CHOH.CH2OH and -CH2.COOH, plus the unsubstituted phenoxathiin-10,10-dioxide.

Screening of unsubstituted cyclic compounds as inhibitors of monoamine oxidases

A number of unsubstituted aromatic hydrocarbons, azaheterocycles, oxaheterocycles and cyclic ketones were screened for their inhibitory potency towards monoamine oxidases (MAO; EC 1.4.3.4.) A and B. Fair activities (IC50 10-100 microM) and selectivities were found for, e.g. naphthalene, anthracene, phenanthrene, isoquinoline and acridine. The most active inhibitors are oxygen-containing compounds (e.g. coumarin, flavone, dibenzofuran, xanthene, thioxanthone and acridone), with xanthone emerging as a potent (IC50 0.8 microM) and reversible MAO-A inhibitor. All tested inhibitors seem to act in a reversible and time-independent manner.

Can our knowledge of monoamine oxidase (MAO) help in the design of better MAO inhibitors?

This paper presents a rapid overview of the mechanism by which monoamine oxidase (MAO) catalyzes the deamination of its substrates, and highlights the stereoselective nature of the active site of the enzyme. With the help of a few selected examples it is also discussed which structural factors are thought to have a preponderant influence on the affinity and selectivity of molecules towards the active site of either form of MAO. From the currently available data on the enzyme and its inhibition, it clearly appears that new MAO inhibitors, of whatever type, could be easily designed by structural modulation of molecules already found to have MAO inhibitory properties. As to whether better MAO inhibitors could be envisaged, it is suggested that MAO inhibition might be advantageously combined with other pharmacological properties for the treatment of pathological conditions, such as stroke and epilepsy, to the occurrence of which MAO activity might contribute. The rationale of this approach is presented.