Abstract
Osmanthus fragrans var. aurantiacus is utilized as a medicinal herb and prized tea in the orient for treating various ailments such as respiratory issues, digestive problems, and stress-related conditions. In this study, we searched for new neuroprotective ingredients in an effective strategy from the extract. By strategically applying molecular networking based on LC-QTOF MS/MS, four new furofuran-type lignans (1-4) were isolated from O. fragrans var. aurantiacus, showcasing the latest tools and techniques in research. Moreover, the absolute configuration of new compounds was evaluated by ECD spectral calculations, and derivatives were produced through chemical reactions. The isolated compounds were investigated for their neuroprotective activity against oxidative stress in L-glutamate-induced HT22 cells. Among the compounds, aurantiosides C-D (3-4) showed significant neuroprotective activity. Furthermore, molecular docking and dynamic studies of Kelch-like ECH-associated protein 1 (Keap1), an enzyme that regulates the nuclear factor erythroid 2-related factor 2 (Nrf2) that acts under oxidative stress, were conducted with these active compounds to investigate their underlying neuroprotective mechanisms. Western blot analysis further supported the neuroprotective effect of aurantioside D (4) by showing reduced Keap1 protein expression in L-glutamate-exposed HT22 cells. Overall, this study demonstrates that molecular networking based on MS/MS fragment analysis is an effective strategy for the discovery and characterization of novel neuroprotective furofuran lignan glucosides from O. fragrans var. aurantiacus.