Novel secondary metabolites from the endobryophytic fungus Botrysphaeria laricina and their biological activity

Abstract

One novel polyketide synthase-nonribosomal peptide synthetase (PKS-NRPS) hybrid metabolite, laricinin A (1), two new meroterpenoids, tricycloalternarenes X and Y (2 and 3), one new coumarin, 3,4,7-trihydroxy-6-methylcoumarin (4), together with the known ethyl acetylorsellinate (5), diorcinol K (6), and tricycloalternarenes C and D (7 and 8) were obtained from culture of the fungus Botrysphaeria laricina isolated from the moss Rhodobryum umgiganteum. The structures of the new compounds were elucidated based on extensive spectroscopic techniques including HRMS and 1D and 2D NMR measurements. The absolute configuration of compound 1 was determined by ECD calculation and it was the first example of a novel group of PKS-NRPS hybrids possessing an unprecedented methyldihydropyran-isobutylpyrrolidinone skeleton. Compounds 2, 7, and 8 showed significant quinone reductase inducing activity in Hepa 1c1c7 cells.

Keywords: Botrysphaeria laricina; ECD calculation; Laricinin A; Quinone reductase inducing activity; Tricycloalternarenes.