Taxonomy Driven Discovery of Polyketides from <i>Aspergillus californicus</i>
Yaojie Guo, Ling Ding, Simone Ghidinelli, Charlotte H. Gotfredsen, Mercedes de la Cruz, Thomas A. Mackenzie, María C. Ramos, Pilar Sánchez, Francisca Vicente, Olga Genilloud, Sonia Coriani, René Wugt Larsen, Jens C. Frisvad, Thomas Ostenfeld Larsen
Abstract
Five new polyketides were isolated from the rare filamentous fungus Aspergillus californicus IBT 16748 including calidiol A (1); three phthalide derivatives califuranones A1, A2, and B (2–4); and a pair of enantiomers (−)-calitetralintriol A (−5) and (+)-calitetralintriol A (+5) together with four known metabolites (6–9). The structures of the new products were established by extensive spectroscopic analyses including HRMS and 1D and 2D NMR. The absolute configurations of two diastereomers 2 and 3 and the enantiomers (−5) and (+5) were assigned by comparing their experimental and calculated ECD data, whereas the absolute configuration of 4 was proposed by analogy. Compound 1 showed moderate activity against methicillin-resistant Staphylococcus aureus.