An undescribed alkaloid from Crinum latifolium L.: structural elucidation and evaluation of its biological activity

From the whole plant of Crinum latifolium L. collected in Vietnam, eight Amaryllidaceae alkaloids were isolated and characterised, including one previously undescribed compound, (1S)-1-hydroxyungeremine (1), together with seven known alkaloids: (+)-crinamine (3), ungeremine (4), (+)-vittatine (5), (+)-dihydroepivittatine (6), (+)-dihydrohamayne (7), and (+)-bulbispermine (8). The structures of all compounds were elucidated by comprehensive spectroscopic analysis, including 1D and 2D NMR experiments and high-resolution electrospray ionisation mass spectrometry (HR-ESI-MS). All isolated alkaloids were evaluated for acetylcholinesterase (AChE) inhibitory activity, nitric oxide (NO) production inhibition, and cytotoxic effects. Among them, ungeremine (4) exhibited the most potent AChE inhibitory activity, with an IC₅₀ value of 0.39 ± 0.03 µM, which was significantly stronger than that of the positive control galantamine (IC₅₀ = 2.40 ± 0.45 µM). (+)-Crinamine (3) demonstrated notable anti-inflammatory and cytotoxic activities, showing an IC₅₀ value of 0.85 ± 0.04 µM for NO inhibition (positive control L-NMMA, IC₅₀ = 7.80 ± 0.36 µM), and IC₅₀ values of 11.82 ± 1.09 µM and 10.38 ± 0.82 µM against HepG2 and LNCaP cell lines, respectively. The new alkaloid, 1-hydroxy-ungeremine (1), displayed moderate AChE inhibitory activity (IC₅₀ = 12.24 ± 1.08 µM). These findings further support C. latifolium as a valuable source of bioactive Amaryllidaceae alkaloids with potential therapeutic applications.