Sativene-Related Sesquiterpenoids with Phytotoxic and Plant-Promoting Activities from the Plant Pathogenic Fungus <i>Bipolaris sorokiniana</i> Based on a Molecular Networking Strategy

Sativene-related sesquiterpenoids including <i>seco</i>-sativene analogs are a large member of fungal secondary metabolites with phytotoxic and growth-promoting effects on different plants. In this report, a series of sativene-related sesquiterpenoids with diverse carbon skeletons (<b>1</b>-<b>9</b>, sativene/isosativene/<i>seco</i>-sativene/cyclosativene/<i>seco</i>-isosativene ring systems) were isolated from the plant pathogenic fungus <i>Bipolaris sorokiniana</i> based on a molecular networking strategy. The undescribed structures were elucidated based on NMR spectra, X-ray diffraction analysis, chemical derivation, and calculated electronic circular dichroism calculations. Bipolaric acid (<b>1</b>) has a bicyclo[3.2.1] nonane skeleton (<i>seco</i>-sativene), bipolarone (<b>2</b>) is a unique cage-like cyclosativene sesquiterpenoid first isolated from fungi, and bipolariols A (<b>3</b>) and B (<b>4</b>) contain a novel octahydro-1,4-ethano isobenzofuran ring system (<i>seco</i>-isosativene). The possible biosynthetic pathways of these sesquiterpenoids (<b>1</b>-<b>9</b>) were proposed based on their structural features. Drechslerine B (<b>8</b>) exhibited phytotoxic activities to green foxtails, and compounds <b>5</b>-<b>7</b> and <b>9</b> showed growth-promoting effects with varying degrees on seedling growth of <i>Arabidopsis thaliana</i>.