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

Sativene-related sesquiterpenoids including seco-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 (1-9, sativene/isosativene/seco-sativene/cyclosativene/seco-isosativene ring systems) were isolated from the plant pathogenic fungus Bipolaris sorokiniana 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 (1) has a bicyclo[3.2.1] nonane skeleton (seco-sativene), bipolarone (2) is a unique cage-like cyclosativene sesquiterpenoid first isolated from fungi, and bipolariols A (3) and B (4) contain a novel octahydro-1,4-ethano isobenzofuran ring system (seco-isosativene). The possible biosynthetic pathways of these sesquiterpenoids (1-9) were proposed based on their structural features. Drechslerine B (8) exhibited phytotoxic activities to green foxtails, and compounds 5-7 and 9 showed growth-promoting effects with varying degrees on seedling growth of Arabidopsis thaliana.