Reversed-phase liquid chromatography method to determine COL-3, a matrix metalloproteinase inhibitor, in biological samples

A reversed-phase high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) detection was developed and validated for the quantification of 6-deoxy-6-demethyl-4-dedimethylamino-tetracycline (COL-3), a matrix metalloproteinase (MMPs) inhibitor, in rat serum. This simple, sensitive, rapid and reproducible assay involved a preliminary serum deproteinization by adding a mixture of acetonitrile–methanol–0.5 M oxalic acid (70:20:10 (v/v)), as the combined precipitant and metal blocking agent, into serum samples (2:1 (v/v)). An aliquot (20 μl) of the supernatant was injected into the HPLC system linked to a Waters XTerra™ RP18 column (150 mm×4.6 mm i.d., particle size 5 μm). The compound was eluted by a mixture of acetonitrile–methanol–0.01 M oxalic acid (40:10:50 (v/v), pH 2.00), as the mobile phase, and detected at the wavelength of 350 nm. The total running time was 10 min. The low and high concentration calibration curves were linear in the range of 50–1200 ng/ml and 1200–12,000 ng/ml, respectively. The intra- and inter-day coefficients of variation at three quality control concentrations of 100, 1200, and 12,000 ng/ml were all less than 6%, while the percent error ranged from −2.5 to 6.6%. The limit of quantitation (LOQ) for COL-3 in serum was 50 ng/ml. This assay was successfully employed to study the serum concentration–time profiles of COL-3 after its intravenous and oral administration in rats. The method with some minor modifications in sample pretreatment was also applicable to the determination of the concentrations of COL-3 in rat bile, urine and feces.