Antifungal lipids produced by lactobacilli and their structural identification by normal phase LC/atmospheric pressure photoionization−MS/MS.

Lactobacillus hammesii converts linoleic acid into an antifungal hydroxy fatty acid. High speed counter-current chromatography (HSCCC) using a hexane/ethyl acetate/methanol/water solvent system [3.5:1.5:3:2 (v/v/v/v)] allowed isolation of the antifungal hydroxy fatty acid. A method was developed for characterization of antifungal hydroxy fatty acids using normal phase liquid chromatography combined with atmospheric pressure photoionization-tandem mass spectrometry (LC/APPI-MS/MS). The position of unsaturations and hydroxyl groups was determined directly from crude lipid extracts and their hydroxylated derivatives. The antifungal compounds were identified as a racemic mixture of 10-hydroxy-cis-12-octadecenoic and 10-hydroxy-trans-12-octadecenoic acid. Additionally, HSCCC and LC/APPI-MS/MS methods were used to elucidate the pathway of conversion of linoleic acid by Lactobacillus sanfranciscensis , Lactobacillus plantarum , and L. hammesii to hydroxy fatty acids and conjugated linoleic acid. This study links previously reported 10-hydroxy-12-octadecenoic acid producing Lactobacillus strains to antifungal activities.