USE OF CAFFEINE AS A PROBE FOR RAPID-DETERMINATION OF CYTOCHROME-P-450 CYP1A2 ACTIVITY IN HUMANS

AIM: To develop a rapid HPLC method for the determination of cytochrom e P-450 CYP1A2 activity. METHODS: A 300-mu L plasma was prepared by ex traction with 5-mL chloroform/isopropanol (9:1), and beta-hydroxylethe ophylline was added as internal standard (IS). Samples were separated on an ODS column by a gradient elution system, of which mobile phase c onsisted of 0.05 % acetic acid, acetonitrile, and methanol. The compou nds of interest were monitored at 282 nm by UV detector. RESULTS: No p otential interfering peaks were found. Paraxanthine (17X), IS and caff eine (137X) were rapidly eluted with baseline resolution, and their re tention time was less than 13 min. The detection Limits of both 17X an d 137X were 0.1 mu mol.L-1. Linear relations ranged over 1-100 mu mol. L-1 and 1-200 mu mol.L-1 with correlation coefficient of 0.9999 and 0. 9987, respectively, for 17X and 137X. The coefficients of variation we re within 6 % for 17X, and 10 % for 137X. The average recoveries for b oth compounds were ranged from 96 % to 108 %. CONCLUSION: This method is sensitive and rapid, and can be used for population studies of CYP1 A2.