HLE-Inhibitory Alkaloids with a Polyketide Skeleton from the Marine-Derived Fungus Coniothyrium cereale

The marine endophytic fungus Coniothyrium cereale produces the structurally unusual polyketide-type alkaloids (−)-cereolactam (1) and (−)-cereoaldomine (3), incorporating a lactam and an imine functionality, respectively, as well as the related metabolite (−)-trypethelone (2). Compounds 1 and 3 showed selective inhibition of human leukocyte elastase with IC50 values of 9.28 and 3.01 μM, respectively. Compound 2 was found to be inhibitory toward Mycobacterium phlei, Staphylococcus aureus, and Escherichia coli and also cytotoxic against mouse fibroblast cells (IC50 = 7.5 μM).