eng Oriental Scientific Publishing Company Biosciences Biotechnology Research Asia 0973-1245 2016-03-12 5 2 541 544 7136 article O. I Oloyede 1 Department of Biochemistry, University of Ado-Ekiti (Nigeria) The effect of Azadirachta indica (leaf extract) on some enzyme activities in the heart was investigated. These enzymes include Aspartate transaminase, Alanine transaminase and Alkaline phosphatase. The result obtained showed a decrease in the activities of aspartate transaminase and alkaline phosphatase in the heart (P<0.05) after the administration of first dose. The reduction in aspartate transaminase activities continued to the termination of experiment (seventh day). Generally, the activities of all the enzymes studied reduced on the seventh day. Reduction of alkaline phosphatase activity in the heart is with a corresponding increase in the serum on the third day of administration. This reflects tissue damage which might have been done to the plasma membrane with corresponding efflux of the cytoplasmic content of the enzyme into extracellular space. Though, recovery of aspartate transaminase and alkaline phosphatase on the third day after administration of the second dose, indicates denovo synthesis of enzyme molecules. The result obtained shows that continual usage of the leaf extract of Azadirachta indica may lead to cell destruction and initiation of heart diseases. https://www.biotech-asia.org/vol5no2/toxicological-studies-on-the-leaf-extract-of-azadirachta-indica-in-the-heart-of-rat-rattus-novegicus/ Azadirachta indica; alanine transaminase; aspartate transaminase