Assessment of Tonica, an Aqueous Herbal Haematinic, in the Modulation of Rat Hepatic Microsomal CYP-Mediated Drug Metabolizing Enzymes: Implications for Drug Interactions

摘要

The effects of Tonica (TN), an herbal haematinic prepared from the stem barks of Khaya senegalensis, Mitragyna stipulosa and Kigelia africana, on the activities of hepatic microsomal cytochrome P450 (CYP) enzymes were investigated in Sprague-Dawley rats. TN was administered to rats, by oral gavage, at the normal human dose (28 mg/kg/day), l0x and 20x that dose for 6 weeks. Activities of certain hepatic CYP drug-metabolizing enzymes and pentobarbital-induced sleeping time were determined in control and TN-treated animals. There were insignificant (p>0.05) increases in the microsomal protein content (3.25-31 %) at all doses of TN in a non-dose-dependent fashion. However, there was a general insignificant attenuation of NADPH cytochrome c (P_450) reductase activity in TN-treated animals compared to control (8.9-26.1%). p-Nitrophenol hydroxylase (pNPH) activity was insignificantly (p>0.05) elevated (14.8-23%) in the TN-treated rats compared to control.