3. Molecular modelling analysis of the
metabolism of cocaine
Fazlul
Huq
School of Biomedical Sciences, Faculty of Health Sciences, The
University
of
Sydney
E-mail :
f.huq@fhs.usyd.edu.au.
Abstract:
Cocaine is one of the main alkaloids
of Erythroxylum coca that has a long history of human use and abuse.
Cocaine acts as a local anaesthetic and stimulant causing increased
alertness and a sense of euphoria. Sustained abuse of cocaine as a
recreational drug is widespread around the world. Cocaine abuse during
pregnancy is of major concern in certain countries where pregnant
women take several drugs along with cocaine because it is known that
cocaine can cross placenta. Cocaine has been reported to cause
toxicity mainly to cardiovascular system and to a lesser extent to the
liver. Cocaine is extensively metabolised in humans so that only a
small percentage is excreted unaltered in urine. Cocaine is
metabolized in vivo to pharmacologically inactive metabolites ecgonine
methyl ester (ECG), benzoylecgonine (BE) and ecgonine (ECG). Among the
metabolites BE has six times longer half-life than cocaine. Norcocaine
is a relatively minor metabolite in humans. Molecular modelling
analyses show that among cocaine and its metabolites, the metabolite
cocaine N-oxide has the lowest LUMO-HOMO energy difference indicating
that it has the greatest kinetic lability. The surface of the
metabolite is also found to abound in electron-deficient regions so
that it can cause oxidation of reduced form of glutathione and that of
nucleobases in DNA, thus compromising the antioxidant status of the
cell and inducing damage to DNA.
Key words:
cocaine, norcocaine, ecgonine, cocaethylene, molecular modelling
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