Biochemometric-guided isolation of new Isosteroidal alkaloids from Fritillaria cirrhosa D.Don (Liliaceae, syn. Fritillaria roylei Hook) as acetylcholinesterase inhibitors

Globally, Alzheimer's disease is an urgent public health concern with the ageing population in developing nations. Recent studies have identified isosteroidal alkaloids as promising therapeutic agents for Alzheimer's treatment. Fritillaria species are well-known rich sources of steroidal and isosteroidal alkaloids. In this context, the current study focuses on the biochemometric-guided isolation of three previously undescribed and two known isosteroidal alkaloids as acetylcholinesterase (AChE) inhibitors from the bulbs of Fritillaria cirrhosa D.Don. The isolated molecules were characterized by NMR, HR-ESI-MS, FT-IR, and DP4+ analysis. Subsequently, all isolates were evaluated for AChE inhibitory activity using Ellman's method. Among the evaluated molecules, 1 (IC₅₀: 33.0 ± 4.4 μM) and 5 (IC₅₀: 24.7 ± 4.5 μM) showed promising AChE inhibition in vitro. Enzyme kinetic studies of isolated molecules revealed mixed inhibition kinetics with K_i varying from 1.3 to 24.4 μM. Moreover, the in silico studies showed excellent binding affinities of isolated molecules with the target protein and good drug-like ADMET properties. The present study identified new isosteroidal alkaloids as promising AChE inhibitors from F. cirrhosa bulbs via a biochemometric approach and advocated their further exploration for treating neurodegenerative disorders.