Identification of isoprenoid-type components in human expired air: a possible shunt pathway in sterol metabolism

Expired air samples have been analyzed from three groups of human subjects (normal, liver dysfunction, lung cancer) and the baboon (Papio anubus). Of the several hundred compounds present, three compounds were of particular interest due to their structural relationship to the isoprenoid-type intermediates in the sterol pathway. These compounds were 1-methyl-4-(1-methyl-ethenyl)-cyclohexene, 6-methyl-5-hepten-2-one, and 6,10-dimethyl-5,9-undecadien-2-one. Hydroxyacetone was also found in all samples screened. The relationship of these compounds to the non-sterol pathway of mevalonate metabolism is discussed.