Effects Of A Methanol Extract Of Eurycoma Longifolia On The Uptake And Release Of Dopamine In Rat Brain Synaptosomes






Eurycoma longifolia, alkaloid , dopamine


The effects of the crude alkaloid fraction of Eurycoma longifolia root on the release and uptake of dopamine was investigated in vitro using rat brain synaptosomes. Synaptosomes were pre-loaded with [3H]dopamine and then incubated with the crude alkaloid fraction dissolved in Krebs bicarbonate buffer. Pre-loaded synaptosomes incubated with Krebs bicarbonate buffer alone served as controls. The amount of radioactivity released into the incubation medium was measured by liquid scintillation counting. To investigate the effect of the crude alkaloid fraction on the uptake of dopamine, synaptosomes were incubated with [3H]dopamine in the presence or absence of the crude alkaloid fraction. The amount of radioactivity not taken up was measured. The crude alkaloid fraction was found to enhance the release of dopamine from the synaptosomes but had no significant effect on the uptake of dopamine. The crude alkaloid fraction was separated into 5 major fractions, denoted as Fraction 1, 2, 3, 4 and 5, using reversed phase high performance liquid chromatography (RP-HPLC) with gradient elution. Fraction 2 and Fraction 4 were found to increase significantly the release of dopamine from synaptosomes while Fraction 1 was found to reduce the uptake of dopamine by synaptosomes. Thin-layer chromatography (TLC) revealed that Fraction 2 consisted of at least two components.