Abstract
Four new lycodine-type alkaloids, namely 16-hydroxyhuperzine B (1), N-methyl-11-acetoxyhuperzine B (2), 8,15-dihydrolycoparin A (3) and (7S, 12S, 13R)-huperzine D-16-O-β-d-glucopyranoside (4), along with ten known analogues 5−14, were isolated from the whole plant of Lycopodiastrum casuarinoides. The structures of the new compounds were elucidated by means of spectroscopic techniques (IR, MS, NMR, and CD) and chemical methods. Compounds 1 and 2 possessed four connected six-membered rings, while compounds 3 and 4 were piperidine ring cleavage products. In particular, compound 4 was a lycopodium alkaloidal glycoside which is reported for the first time. Among the isolated compounds N-demethylhuperzinine (7), huperzine C (8), huperzine B (9) and lycoparin C (13) possessed significant inhibitory activity against acetylcholinesterase, and the new compound 1 showed moderate inhibitory activity. The structure activity relationships were discussed.
Highlights
Alzheimer’s Disease (AD) is a chronic neurological disorder characterized by memory impairment, cognitive dysfunction, behavioral disturbances and deficits in activities of daily living [1,2,3]
A bioactivity-guided separation of the alkaloidal extracts of L. casuarinoides led to four new and ten known lycodine-type alkaloids
Within the series of lycodine-type alkaloids tested for AChE inhibiting activity, N-demethylhuperzinine (7), huperzine C (8), huperzine B (9) and lycoparin C (13) showed significant AChE inhibitory activity, with inhibited the hydrolysis of acetylthiocholine by 50% (IC50) values of 1.9, 0.6, 20.2 and
Summary
Alzheimer’s Disease (AD) is a chronic neurological disorder characterized by memory impairment, cognitive dysfunction, behavioral disturbances and deficits in activities of daily living [1,2,3]. Recent studies have shown that AChE inhibitors prevent the assembly of β-amyloid peptide into amyloid plaque which is the first step of AD [5,6]. This discovery further stimulated a great interest in searching for useful leads which could become new candidates for the development of rational drug design against AD. According to previous reports and our research, it was found that the total alkaloidal extract of the plant exhibited significant AChE inhibitory activity [8,10,11,12,13].
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