ABSTRACT
<p><b>OBJECTIVE</b>To study the inhibitory effect of total saponins of the root and rhizome of Panax notoginseng (PNS) on drug metabolism enzyme CYP3A in rat livers and its kinetic analysis.</p><p><b>METHOD</b>Microsome enzyme was prepared by differential velocity centrifugation. Michaelis constant (Km) and maximum velocity (Vmax) of CYP3A, 50% inhibitory concentration of PNS on CYP3A, and the inhibition type and the inhibition constant of CYP3A (Ki, Kis) of PNS on CYP3A were calculated by Lineweaver-Burk and the low of semi-effect-probit.</p><p><b>RESULT</b>Total saponins of the root and rhizome of panax notoginseng inhibited CYP3A activity, with IC50 of 689.54 mg x L(-1). Compared with the substrate aminopyrine, CYP3A showed Km of 0.036 mmol x L(-1) and Vmax of 21.01 micromol min(-1) x g(-1). Total saponins of the root and rhizome of panax notoginseng showed a mixed inhibition on CYP3A, with the inhibition constants of 247.79 mg x L(-1) (Ki) and 321.79 mg x L(-1) (Kis).</p><p><b>CONCLUSION</b>Total saponins of the root and rhizome of panax notoginseng have a significant effect on CYP3A activity in rat livers.</p>