Characterization of four new antifungal yanuthones from Aspergillus niger

Four new yanuthone analogs (1-4) were isolated from the filamentous fungus Aspergillus niger. The structures of the new compounds were elucidated on the basis of UHPLC-DAD-HRMS data and one-dimensional and two-dimensional NMR spectroscopy. Labeling studies with (13)C8-6-methylsalicylic acid identified three class I yanuthones originating from the polyketide 6-methylsalicylic acid (yanuthone K, L and M (1-3)) and a class II yanuthone, which was named yanuthone X2 (4). The four new compounds were tested toward the pathogenic yeast Candida albicans and all displayed antifungal activity. Yanuthone X2 represents the first example of a bioactive class II yanuthone, demonstrating the pharmaceutical potential of this class.