Two New 4-Hydroxy-2-pyridone Alkaloids with Antimicrobial and Cytotoxic Activities from Arthrinium sp. GZWMJZ-606 Endophytic with Houttuynia cordata Thunb.

Two new 4-hydroxy-2-pyridone alkaloids furanpydone A and B ( 1 and 2 ), along with two known compounds N-hydroxyapiosporamide ( 3 ) and apiosporamide ( 4 ) were isolated from the endophytic fungus Arthrinium sp. GZWMJZ-606 in Houttuynia cordata Thunb. Furanpydone A and B had unusual 5-(7-oxabicyclo[2.2.1]heptane)-4-hydroxy-2-pyridone skeleton. Their structures including absolute configurations were determined on the basis of spectroscopic analysis, as well as the X -ray diffraction experiment. Compound 1 showed inhibitory activity against ten cancer cell lines (MKN-45, HCT116, K562, A549, DU145, SF126, A-375, 786O, 5637, and PATU8988T) with IC 50 values from 4.35 to 9.72 µM. Compounds 1 , 3 and 4 showed moderate inhibitory effects against four Gram-positive strains ( Staphylococcus aureus , methicillin-resistant S. aureus , Bacillus Subtilis , Clostridium perfringens ) and one Gram-negative strain ( Ralstonia solanacarum ) with MIC values from 1.56 to 25 µM. However, compounds 1 - 4 showed no obvious inhibitory activity against two Gram-negative bacteria ( Escherichia coli and Pseudomonas aeruginosa ) and two pathogenic fungi ( Candida albicans and Candida glabrata ) at 50 µM. These results show that compounds 1 - 4 are expected to be developed as lead compounds for antibacterial or anti-tumor drugs.