COMT assay

COMT activity was evaluated by the ability of homogenates to methylate adrenaline to metanephrine. Aliquots of 0.5 ml of the homogenate were preincubated for 20 min with 0.5 ml of phosphate buffer (0.5 mM); thereafter, the reaction mixture was incubated for 30 min with increasing concentrations of adrenaline (5 to 500 uM) in the presence of a saturating concentration (100 /M) of the methyl donor (S-adenosyl-L-methionine); the incubation medium contained also pargyline (100 gM), MgCl2 (100 gM) and EGTA (1 mM). The preincubation and incubation were carried out at 37℃, in conditions of light protection, with continuous shaking and without oxygenation. In experiments conducted with the aim of studying the inhibitory effect of tolcapone on COMT activity, tissue homogenates were preincubated for 15 min with increasing concentrations of tolcapone (0.5 to 10,000 nM); the incubation was performed in the presence of a concentration of adrenaline three times the corresponding Km value, as determined in saturation experiments for each age group. At the end of the incubation period the tubes were transferred to ice and the reaction was stopped by the addition of 100 ul of perchloric acid (2 M). The samples were then centrifuged (200 g, 4 min, 4C), and 500 Ml aliquots of the supernatant filtered on Millipore microfilters (MF1) were used for the assay of metanephrine. This procedure allows 99% extraction of catecholamines and their methylated metabolites.

Cell lines

SH-SY5Y neuroblastoma cells

Preparation method

Soluble in DMSO > 10 mM. General tips for obtaining a higher concentration: Please warm the tube at 37 ℃ for 10 minutes and/or shake it in the ultrasonic bath for a while. Stock solution can be stored below -20℃ for several months.

Reaction Conditions

6 days

Applications

Tolcapone as an inhibitor of COMT shows a protective effect against HIV associated dendritic and synaptic damage.

Animal models

Male albino rats (Fii-albino, 270-300 g)

Dosage form

Orally in a final volume of 2 ml/kg.

Preparation method

Suspended in saline containing 1% Tween 80 using a glass homogenizer.

Applications

Tolcapone is very effective in increasing the striatal extracellular levels of L-DOPA and dopamine in the rat, when given in combination with L-DOPA+benserazide.

Other notes

Please test the solubility of all compounds indoor, and the actual solubility may slightly differ with the theoretical value. This is caused by an experimental system error and it is normal.

Tolcapone is a novel, reversible and orally-bioavailable small-molecule catechol-O-methyltransferase (COMT) inhibitor used for as an adjunct to levodopa therapy for the treatment of Parkinson’s disease (PD). The chemical structure of tolcapone contains a catechol structure with two electron withdrawing substituents of a tendency to easily deliver a proton resulting in an anion that is highly affinitive for COMT (the value of 50% inhibition concentration IC₅₀of 36 nM in rat liver) and displaces other catechols (such as catecholamines and levodopa) from the COMT catalytic center to prevent methylation. Study results have that the use of tolcapone reduces the dosage but enhances the therapeutic effects of levodopa to control PD symptoms.

Reference

[1].Truong DD. Tolcapone: review of its pharmacology and use as adjunctive therapy in patients with Parkinson's disease. Clin Interv Aging. 2009;4:109-113
[2].Jorga K, Fotteler B, Heizmann P, Gasser R. Metabolism and excretion of tolcapone, a novel inhibitor of catechol-O-methyltransferase. Br J Clin Pharmacol. 1999; 48(4):513-520.