The mixture of conjugated diene hyperperoxide isomers obtained from autoxidation of methyl linoleate was separated by high performance liquid chromatography (HPLC). Four major isomers were obtained from adsorption chromatography and identified as the 9 and 13 positional isomers having the trans-trans and cis-trans configurations. The latter geometrical isomers have the trans double bond adjacent to the hydroperoxide group. The hydroxy compounds (methyl hydroxylinoleates) obtained from the hydroperoxides by NaBH4 reduction were similarly separated but with improved resolution. This is the first instance of the complete separation of these compounds and provides a rapid method for their analysis. Unlike adsorption chromatography, reversed-phase chromatography separates the mixtures only according to the geometrical isomerism of the double bonds and not according to the position of the hydroxy or hydroperoxide function.

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Samples of red-coloured lettuce and chicory were assessed for bitterness by sensory analysis and compared with conventional green-coloured varieties. The amounts of the sesquiterpene lactones lactucin, 8-deoxylactucin and lactucopicrin and their glycosides were determined using enzyme hydrolysis and high performance liquid chromatography. The level of each of these compounds was compared with the bitterness score found for each sample, and the resulting correlation data suggested that the increasing level of one of these compounds, lactucin glycoside, was closely related to the increase in bitterness.

Examination of sputum for eosinophils and measurement of exhaled nitric oxide have been proposed as noninvasive methods of assessing airway inflammation in asthma. The use of these tests in the evaluation of patients with occupational asthma has not been reported. This study investigated the changes in sputum eosinophils and exhaled NO before and at intervals after inhalation challenge with plicatic acid in patients with suspected western red cedar asthma. Of 17 subjects who underwent challenge, nine had a positive bronchoconstrictor reaction (responders) and eight had a negative reaction (nonresponders). At 6 and 24 h after plicatic acid challenge, there was a significant increase in sputum eosinophils among responders, which was inversely related to the fall in forced expiratory volume in one second (FEV1) at 6 h. An increase in sputum eosinophils was also found in three nonresponders. Levels of exhaled NO increased at 24 h after challenge with plicatic acid in both responders and nonresponders, being significant only in nonresponders. No correlation was found between the increase in nitric oxide and the magnitude of the functional changes in the airways. There were significant correlations between the degree of sputum eosinophilia and the level of exhaled NO before and after methacholine and plicatic acid challenge. In conclusion, the late asthmatic reaction induced by plicatic acid in patients with western red cedar asthma is associated with an increase in sputum eosinophils. The usefulness of measuring sputum eosinophils and exhaled nitric oxide in the clinical evaluation of patients with suspected occupational asthma caused by low molecular weight compounds has yet to be determined.

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Incubation of linoleic acid with crude homogenate of tomato fruit gave a high yield (69%) of linoleic acid hydroperoxides with a ratio of 9- to 13-hydroperoxide isomers of 96:4. After chromatography of the products, as free acids or methyl esters, hydroperoxides with 9- to 13-isomeric ratios of greater than 99:1 were obtained. The major product was characterized as 9-D-hydroperoxy-octadeca-trans-10,cis-12-dienoic acid. The results demonstrate the positional specificity of lipoxygenase from tomato fruit.

a-Tocopherol substantially affects the distribution of peroxidic compounds formed during the autoxidation of methyl linolenate and methyl linoleate. In the autoxidation of both these unsaturated fatty acid esters the proportion of monohydroperoxides with conjugated double bonds in the trans, trans configuration is reduced until at high concentrations of a-tocopherol (5 %) only cis, trans isomers are formed. In the autoxidation of methyl linolenate the proportion of hydroperoxy-epidioxides is reduced and only monohydroperoxides are formed when 5 % a-tocopherol is present. The results are discussed in terms of recent findings concerning the mechanism of the autoxidation of unsaturated lipids.