A Cedrane and a Fusarin From the Algicolous Fungus Fusarium graminearum 12II2N and Response to Mycoparasitism

Abstract

The fungal genus Fusarium is a treasure-trove of structurally diverse secondary metabolites, contributed greatly by marine-derived strains. A new cedrane sesquiterpene, fusacedrol (1), and a new fusarin member, fusarin M (2), were isolated from Fusarium graminearum 12II2N that was isolated as an endophyte from the marine brown alga Sargassum sp. The planar structures of compounds 1 and 2 were incisively identified by analysis of spectroscopic data, inclusive of NMR and MS, and the relative configurations were ensured by NOESY correlations and a coupling constant. Quantum chemical calculations of specific optical rotations of compound 1 and cedrol solved the absolute configuration of compound 1. Compound 1 represents the first new cedrane derivative with a 5/5/6 tricyclic nucleus from marine-derived fungi, and this skeleton has also been reported rarely from other marine organisms. Compound 2 is an isomer of fusarin Y, and its production could be greatly reduced by coculture with Trichoderma flagellatum 12A1N of the same origin. The two isolates were assayed for inhibiting the bacterium Pseudoalteromonas citrea (bio-02684, a green-spot pathogen of Porphyra), but none of them were active unfortunately.