Isolation, structures, and antifungal activities of new aureobasidins

Aureobasidins are a group of cyclic depsipeptides with antifungal activity and are produced by Aureobasidium pullulans. Aureobasidins are composed of eight amino acids and one hydroxy acid such as 2-hydroxy-3-methylpentanoic acid (Hmp), and highly lipophilic. Five new aureobasidins, S1, S2a, S2b, S3 and S4, which have higher hydrophilicity in reversed phase HPLC than the known aureobasidins A-R, were discovered in a fermentation broth of A. pullulans R106 by means of on-line liquid chromatography/mass spectrometry with electrospray ionization. We identified the structures of the compounds and studied their antifungal activities. Three of the new aureobasidins, S2b, S3 and S4, which have hydroxylated Hmp as the hydroxy acid, were highly active against Candida spp. and Cryptococcus neoformans.