Filicinic acid based meroterpenoids with 6/6/6 tricyclic Core from Hypericum elodeoides and their anti-Alzheimer’s disease effects

(±)-Elodeoidileons A-L ( 1 - 12 ), 12 pairs of previously undescribed filicinic acid based meroterpenoids with unique pyran-fused linear or angular 6/6/6 tricyclic skeletons, were isolated from Hypericum elodeoides . Their structures including absolute configurations were determined by modern spectroscopic techniques, nuclear magnetic resonance (NMR), high resolution electrospray ionization mass spectrometry (HR-ESI-MS), calculated electronic circular dichroism (ECD) and NMR, as well as the modified Mosher’s methods. Besides, the possible biosynthetic pathways for 1 - 12 were proposed. Moreover, biological activity assessments suggest that compound 1a may promote β-amyloid (Aβ) clearance by activating Retinoid X receptor-α and upregulating the expression of the ABCA1 protein, showing promise as anti-Alzheimer’s agent.