Antifungal polyketides from the Picea rubens and Vaccinium angustifolium endophyte Lachnellula calyciformis

Abstract

As part of a survey of foliar endophytes of conifers in the Acadian forest, we isolated a strain of Lachnellula calyciformis from a healthy Picea rubens needle. From this fungus, the new natural products deoxylachnellulone (3) and lachnelluloic acid B (5), and the known metabolite lachnellulone (1), were isolated and structurally characterized. Isolachnellulone (2) and isodeoxylachnellulone (4) occurred as isomers resulting from the facile isomerization of lachnellulone (1) and deoxylachnellulone (3), respectively. The natural products lachnellulone (1) and deoxylachnellulone (3) were also confirmed from two strains of L. calyciformis isolated as leaf and stem endophytes of Vaccinium angustifolium in eastern Canada, representing the first record of this species from a non-conifer host. All isolated compounds displayed moderate antifungal and antibiotic activity. This study of biologically active natural products from a conifer endophyte highlights the increasing apparent complexity of their collective life histories.