Delitpyrones: α-Pyrone Derivatives from a Freshwater Delitschia sp.

In research focused on the discovery of new chemical diversity from freshwater fungi, a peak library was built and evaluated against a prostate cancer cell line, E006AA-hT, which was derived from an African American, as this population is disproportionately affected by prostate cancer. The chemical study of the bioactive sample accessioned as G858 (Delitschia sp.) led to the isolation of eight new α-pyrone derivatives (1 – 7, and 11), as well as the new 3S*,4S*-7-ethyl-4,8-dihydroxy-3,6-dimethoxy-3,4-dihydronaphthalen-1(2H)-one (15). In addition, the known compounds 5-(3-S-hydroxybutyl)-4-methoxy-6-methyl-2H-pyran-2-one (8), 5-(3-oxobutyl)-4-methoxy-6-methyl-2H-pyran-2-one (9), pyrenocine I (10), 5-butyl-6-(hydroxymethyl)-4-methoxy-2H-pyran-2-one (12), sporidesmin A (13), 6-ethyl-2,7-dimethoxyjuglone (14), artrichitin (16), and lipopeptide 15G256ε (17) were also obtained. The structures of the new compounds were elucidated using a set of spectroscopic (NMR) and spectrometric (HRMS) methods. The absolute configuration of the most abundant member of each subclass of compounds was assigned through a modified Mosherʼs ester method. For 15, the relative configuration was assigned based on analysis of 3 J values. Compounds 1, 2, 5 – 14, 16, and 17 were evaluated against the cancer cell line E006AA-hT under hypoxic conditions, where compound 13 inhibited cell proliferation at a concentration of 2.5 µM.