LC-MS/MS-Guided Molecular Networking for Targeted Discovery of Undescribed and Bioactive Ophiobolins from Bipolaris eleusines

Anintegrated purification procedure through the LC-MS/MS-basedmolecular networking strategy combined with bioactive evaluation wasfirst ushered for discovering bioactive ophiobolins from Bipolaris eleusines. Ophiobolins were mainly dispersedin five clusters, which were classified based on different ring systemsand functional groups. Nine undescribed ophiobolins (1-6 and 9-11)and an undescribed natural product (8) along with twoknown analogs (7 and 12) were isolated intarget. The undescribed structures were characterized by HR-ESI-MS,NMR spectra, and X-ray diffraction experiments. Compounds 3-12 exhibited strong phytotoxic effects on greenfoxtails by producing visible lesions, and compounds 1-10 and 12 displayed different levelsof cytotoxic activities against cancer cell lines B16, Hep G2, andMCF-7, from which the possible structure-activity relationshipswere then suggested. The results have supported that bioactivity-guidedmolecular networking is an efficient strategy to expedite the discoveryof undescribed bioactive natural products.