Abstract

In the present study dopamine was conjugated with amino acids, glycine, alanine, phenylalanine, and valine, with a view to enhance bioavailability by increasing permeability to brain, lower the rate of clearance by reducing metabolism and eliminate undesirable effects. These conjugates were synthesized and characterized by infrared spectroscopy. The partition coefficient of dopamine and dopamine conjugates was determined in n-octanol and phosphate buffer saline pH 7.4 and the conjugates showed 7 to 10 fold increase in their partition coefficients. Moreover, these conjugates exhibited less protein binding as compared to dopamine and in vitro hydrolysis study revealed that the conjugates have long duration of action because of slow hydrolysis. The reduction in the degree of chlorpromazine-induced catatonia was significantly increased as compared with plain dopamine and combination of levodopa and carbidopa.