Flavanonol Glycosides from the Stems of Myrsine seguinii and Their Neuroprotective Activities

The accumulation of amyloid beta (Aβ) peptides is common in the brains of patients with Alzheimer’s disease, who are characterized by neurological cognitive impairment. In the search for materials with inhibitory activity against the accumulation of the Aβ peptide, seven undescribed flavanonol glycosides (1–7) and five known compounds (8–12) were isolated from stems of Myrsine seguinii by HPLC-qTOF MS/MS-based molecular networking. Interestingly, this plant has been used as a folk medicine for the treatment of various inflammatory conditions. The chemical structures of the isolated compounds (1–12) were elucidated based on spectroscopic data, including 1D and 2D nuclear magnetic resonance (NMR), high-resolution electrospray ionization mass spectrometry (HRESIMS) and electronic circular dichroism (ECD) data. Compounds 2, 6 and 7 showed neuroprotective activity against Aβ-induced cytotoxicity in Aβ(42)-transfected HT22 cells.