Guaiane-type sesquiterpenoids with various ring skeletons from Daphne bholua uncovered by molecular networking and structural revisions of previously reported analogues

Abstract

The genus Daphne is a treasure-house of secondary metabolites with various biological effects, which inspired Daphne bholua being fully investigated phytochemically and biologically for the first time. Here, seven undescribed guaiane-type sesquiterpenoids (1–7) along with thirteen known analogues (8–20) were targeted and isolated from D. bholua using molecular networking. Their chemical structure and configurations were established via NMR spectroscopy analysis, NMR and ECD calculations, Snatzke’s method, along with single-crystal X-ray diffraction technique. Moreover, two pairs of sesquiterpene isomers, either with prominent biological properties or with unprecedented skeleton, were revised by means of computer-assisted structure elucidation, chemical shift calculator using deep learning, etc. The inhibitory potentials of all isolates against acetylcholinesterase were evaluated in vitro and in silico.