Asperlones A and B, Dinaphthalenone Derivatives from a Mangrove Endophytic Fungus Aspergillus sp. 16-5C

Racemic dinaphthalenone derivatives, (±)-asperlone A ( 1) and (±)-asperlone B ( 2), and two new azaphilones, 6′-hydroxy-( R)-mitorubrinic acid ( 3) and purpurquinone D ( 4), along with four known compounds, (？)-mitorubrinic acid ( 5), (？)-mitorubrin ( 6), purpurquinone A ( 7) and orsellinic acid ( 8), were isolated from the cultures of Aspergillus sp. 16-5C. The structures were elucidated using comprehensive spectroscopic methods, including 1D and 2D NMR spectra and the structures of 1 further confirmed by single-crystal X-ray diffraction analysis, while the absolute configuration of 3 and 4 were determined by comparing their optical rotation and CD with those of the literature, respectively. Compounds 1, 2 and 6 exhibited potent inhibitory effects against Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) with IC 50 values of 4.24 ± 0.41, 4.32 ± 0.60 and 3.99 ± 0.34 μM, respectively.