Polyketides from the marine-derived fungus Ascochyta salicorniae and their potential to inhibit protein phosphatases

Abstract

Chemical investigation of the marine fungus Ascochyta salicorniae led to the isolation of two new epimeric compounds, ascolactones A (1) and B (2), in addition to the structurally-related polyketides hyalopyrone (3), ascochitine (4), ascochital (5) and ascosalipyrone (6). The absolute configurations of the epimeric compounds 1 and 2 were assigned as (1R,9R) and (1S,9R), respectively, through simulation of the chiroptical properties using quantum-chemical CD calculations, and chiral GC–MS subsequent to oxidative cleavage (Baeyer–Villiger oxidation) of the side chain.

In silico screening using the PASS software identified some of the A. salicorniae compounds (1–6) as potential inhibitors of protein phosphatases. Compound 4 was found to inhibit the enzymatic activity of MPtpB with an IC₅₀ value of 11.5 μM.