Comparative study of the effects of benzoquinones on mitochondria isolated from rat liver and insect flight muscle

Abstract

This study was intended to investigate the effects of four biologically active benzoquinones namely: maesanin, maesaquinone, juglone and embelin on mitochondria isolated from rat liver and insect flight muscle. These benzoquinones occur naturally in the plant family myrsinaceae. Five species of myrsinaceae have been identified in Kenya and are widely distributed. Several studies have shown that most of the benzoquinones have pharmacological potential and can also protect stored grains against insect pests. There is, however, no report relating the interaction of benzoquinones with insect energy metabolism. Three insect species were used in this study i.e. Schistocerca gregaria (Lipid and carbohydrate metab oltsmg), Periplaneta americana (carbohydrate me1.abolising) and Glos~ina morsitans (amino acid metabolising) . The effects of benzoquinones on energy metabolism was determined by measuring the rate of oxygen consumption, oxidative phosphorylation and ATPase activity. Mitochondria from the insect thoracic muscle and rat liver mitochondria were both prepared by differential centrifugation of the homogenates from the respective tissues. The rate of oxygen consumption was recorded polarographically by an oxygen electrode at 250C in a closed magnetically stirred chamber. ATPase activity was measured enzymatically by pyridine nucleotide coupled assays using Perkin Elmer spectrophotometer. In the absence of benzoquinones (controls) the respiratory control ratios were found to be above 3 for the four types of mitochondria studied, which was an indication that the mitochondria were well coupled and could effectively …