Gas chromatographic-mass spectrometric identification of isosaccharino-1,4-lactone in human serum and urine.

We have identified alpha-isosaccharino-1,4-lactone and beta-isosaccharino-1,4-lactone in the ethyl acetate extract of an ultrafiltrate of blood and of normal human urine, using high-resolution gas chromatography-mass spectrometry. The ultrafiltrate of blood was obtained from three patients on hemodialysis, one with psoriasis vulgaris, one with uremia, and one with amyotrophic lateral sclerosis. The concentration of beta-isosaccharino-1,4-lactone in the ultrafiltrate was two- to threefold that of alpha-isosaccharino-1,4-lactone. Mass fragmentography showed that isosaccharino-1,4-lactone is normally present in human serum in a concentration of 1.7 (SD 1.5) mg/L. In physiological fluid, isosaccharino-1,4-lactone apparently is present in its hydrated form, isosaccharinate.