[Improvement of urinary d-glucaric acid assay and its application]

We propose an improved method to measure urinary D-glucaric acid (GA), which might be of value as an indirect index of the activity of cytochrome P450 (CYP). This method was about 20 times more sensitive than existing methods. Beer's law was obeyed in the concentration range 5.5-66 ng ml(-1) for GA, with the effective molar absorptivity at 533 nm and the relative standard deviation being 9.1 x 10(5) dm(3) mol(-1) cm(-1) and 0.69% (n = 6), respectively. In addition, we introduced the correction value {GA/Cr ratio x10} of urinary GA by measuring urinary creatinine (Cr) at the same time. Based on the proposed method, the GA and Cr values in spot urines of healthy persons and cancer patients were subsequently measured and the correction values of both groups subjected to comparison. As a result, a statistically significant difference was recognized between the two groups.