Isolation and Identification of α-Methyloctanylcarnitines from Human Urine

Abstract

Medium-chain acylcarnitines were isolated from human urine using a combination of chloroform-methanol extraction, silicic acid column and molecular sieving chromatography and preparative HPLC. Three purified acylcarnitines were analyzed by fast atom bombardment mass spectrometry and were also saponified and the free fatty acids analyzed by gas chromatography and mass spectrometry. Combined electron inpact mass spectrometry and fast atom bombardment mass spectrometry and periodate oxidation for location of double bonds, demonstrated the occurrence of .DELTA.6-octenylcarnitine, 2-methyloctanylcarnitine and 2-methyl-.DELTA.6-octenylcarnitine. These acylcarnitines were present in the thirteen urines obtained from normal humans, but were not detected in urines from three individuals who had been on total parenteral nutrition for more than a year. The occurrence of .alpha.-methyl medium-chain acylcarnitines in human urine indicates a role for carnitine in excretion (detoxification) of these acyl derivatives.