Biopesticide Compounds from an Endolichenic Fungus <i>Xylaria</i> sp. Isolated from the Lichen <i>Hypogymnia tubulosa</i>

Endolichenic fungi represent an important ecological group of microorganisms that form associations with photobionts in the lichen thallus. These endofungi that live in and coevolve with lichens are known for synthesizing secondary metabolites with novel structures and diverse chemical skeletons making them an unexplored microbial community of great interest. As part of our search for new phytoprotectants, in this work, we studied the endolichenic fungus <i>Xylaria</i> sp. isolated from the lichen <i>Hypogymnia tubulosa</i>, which grows as an epiphyte on the bark of the endemic Canarian tree <i>Pinus canariensis</i>. From the extract of the liquid fermentation, we isolated two unreported piliformic derivatives, (+)-9-hydroxypiliformic acid (<b>1</b>) and (+)-8-hydroxypiliformic acid (<b>2</b>), along with four previously reported compounds, (+)-piliformic acid (<b>3</b>), hexylaconitic acid A anhydride (<b>4</b>), 2-hydroxyphenylacetic acid (<b>5</b>), and 4-hydroxyphenylacetic acid (<b>6</b>). Their structures were elucidated based on NMR and HRESIMS data. The extract and the isolated compounds were tested for their insect antifeedant (<i>Myzus persicae</i>, <i>Rhopalosiphum padi</i>, and <i>Spodoptera littoralis</i>), antifungal (<i>Alternaria alternata</i>, <i>Botrytis cinerea</i>, and <i>Fusarium oxysporum</i>), nematicidal (<i>Meloidogyne javanica</i>), and phytotoxic effects on mono- and dicotyledonous plant models (<i>Lolium perenne</i> and <i>Lactuca sativa</i>). Compounds <b>4</b>, <b>5</b>, and <b>6</b> were effective antifeedants against <i>M. persicae</i> and <b>4</b> was also active against <i>R. padi</i>. Moreover, <b>3</b> and <b>4</b> showed antifungal activity against <i>B. cinerea</i> and <b>4</b> was the only nematicidal. The extract had a strong phytotoxic effect on <i>L. sativa</i> and <i>L. perenne</i> growth, with compounds <b>3</b>, <b>4</b>, and <b>5</b> identified as the phytotoxic agents, while at low concentrations compounds <b>3</b> and <b>4</b> stimulated <i>L. sativa</i> root growth.