Characterization of metabolic kinetics and CYP phenotyping of aloe emodin in liver microsomes / 国际药学研究杂志

ABSTRACT

Objective To characterize the metabolic kinetics of aloe emodin in human liver microsomes(HLM)and rat liver microsomes(RLM)and identify the CYP phenotyping of phase-metabolism. Methods Aloe emodin was incubated at 37° with HLM and RLM in the presence or absence of NADPH, UDGPA or NADPH+UDGPA. The remaining aloe emodin was determined with a validated LC-MS/MS method to assess the metabolic stability and enzymatic kinetics. A panel of rCYP isoforms(CYP1A2, 2B6, 2C8, 2C9, 2C19, 2D6 and 3A4)and HLM with specific inhibitors of CYP isoforms were used to identify the CYP phenotyping of aloe emodin. Results In HLM and RLM, aloe emodin was metabolically eliminated in the presence of NADPH, with 85.8% and 81.7% of the parent compounds eliminated in 30 min, respectively. The t1/2 were(10.3±0.3)and(11.5±3.3)min, and the CLint were(420.1±10.9) and(573.4±188.2)ml/(min·kg), respectively. The apparent Km and Vmax for HLM and RLM were obtained and found to be(2.4±0.9) and(3.9±1.4)µmol/L, (1492±170.5)and(2783±595.8)nmol/(min·g protein), respectively. In RLM with UDPGA, 38.5% of aloe emodin was metabolized in 30 min with t1/2 of 31.6 min and CLint of(197.1±15.5)ml/(min·kg). The results of CYP phenotyping indicated that CYP1A2, 2B6, 2C19 and 3A4 were the major enzymes involved in the metabolism of aloe emodin. By using the method of total normalized rate, the contributions of the major enzymes were assessed to be 35.4%, 6.6%, 2.2% and 21.9%, respectively. Conclusion Aloe emodin is mainly eliminated by CYP mediated metabolism in HLM and RLM. CYP1A2 and 3A4 are the major responsible enzymes of aloe emodin, and the contributions are above 20%. Species differences in liver metabolism of aloe emodin are observed. It undergoes notable glucuronidation in RLM only.