Antifungal sesquiterpenoids and macrolides from an endophytic Lophodermium species of Pinus strobus

Abstract

A needle endophyte of Pinus strobus (eastern white pine) was isolated from a tree near Sussex, New Brunswick and screened for the production of antifungal compounds. This was identified as Lopherdermium nitens, a common endophyte of white pine known to produce potent antifungal compounds. Extracts of culture filtrates of L. nitens DAOM 250027 were antifungal to the biotrophic pathogen Microbotryum violaceum and the yeast Saccharomyces cerevisiae. Natural products representing two distinct chemical classes were characterized from the crude extract: phenolic bisabolane-type sesquiterpenoids (1–6) and macrolides (7–8).(7R)-(−)-methoxysydonol (1) was isolated as a new structure based on interpretation of spectroscopic data (NMR, OR, UV) and HRMS. Notably, this strain produced both (R)-(−)-(3) and (S)-(+)-sydonol (4), a phenomenon reported in some unrelated species. Pyrenophorin (7) significantly reduced the growth of M. violaceum and S. cerevisiae at 5μM whereas sesquiterpenoids (1–6) were antifungal at 50μM to both species tested including both (R)-(−)- and (S)-(+)-sydonol.