Antifungal polyketides from the Picea rubens and Vaccinium angustifolium endophyte Lachnellula calyciformis
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ORIGINAL ARTICLE
Antifungal polyketides from the Picea rubens and Vaccinium angustifolium endophyte Lachnellula calyciformis David R. McMullin 1 & Joey B. Tanney 2 & Grace J. Daly 1 & J. David Miller 1 Received: 13 July 2020 / Revised: 17 August 2020 / Accepted: 21 August 2020 # German Mycological Society and Springer-Verlag GmbH Germany, part of Springer Nature 2020
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. Keywords Endophytic fungi . Lachnellula . Picea . Vaccinium . Polyketides . Antifungal
Introduction Over the last several decades, we have been interested in the diversity of secondary metabolites from fungal foliar endophytes of conifers in the Acadian forest of New Brunswick and Quebec in Canada, and Maine in the USA. A focus has been endophytes that produce antiinsectan or antifungal compounds that increase the tolerance of the tree to pests and pathogens (Tanney et al. 2018). When inoculated as young seedlings, toxigenic endophyte strains become dominant in the canopy and remain so for decades producing antiinsectan or antifungal metabolites in the needles. For example, the
Section Editor: Marc Stadler Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11557-020-01620-5) contains supplementary material, which is available to authorized users. * J. David Miller [email protected] 1
Department of Chemistry, Carleton University, Ottawa, ON K1S 5B6, Canada
2
Pacific Forestry Centre, Natural Resources Canada, Victoria, BC V8Z 1M5, Canada
needles of white spruce (Picea glauca) seedlings inoculated at an early stage of growth with the rugulosin-producing endophyte Phialocephala scopiformis DAOMC 229536 contain rugulosin at concentrations that affect the growth of the eastern spruce budworm (Choristoneura fumiferana) (McMullin et al. 2018). Two-year field studies showed larval survival and density were reduced on inoculated trees (Quiring et al. 2019, 2020). Griseofulvin-producing strains of Xylaria ellisi were isolated from the canopy of 100-year-old white pine trees (Pinus stro
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