Acetylcholinesterase inhibitory effects of the bulb of Ammocharis coranica (Amaryllidaceae) and its active constituent lycorine

Abstract

Ammocharis coranica (Ker-Gawl.) Herb. (Amaryllidaceae) is used in southern Africa for the treatment of mental illnesses. The ethanol extracts of the bulb of A. coranica and its total alkaloids rich fractions were screened for inhibition of acetylcholinesterase enzyme (AChE), which is implicated in the pathophysiology of Alzheimer's disease. The ethanolic extracts significantly inhibited AChE with IC50 value of 14.3 ± 0.50 μg/ml. The basic ethyl acetate and butanol fractions of the crude extracts were the most active against AChE with IC50 values of 43.1 ± 1.22 and 0.05 ± 0.02 μg/ml respectively. Bioassay-guided fractionation of the basic fractions led to the isolation of lycorine and 24-methylenecycloartan-3β-ol. Lycorine which was isolated from both butanol and ethyl acetate fractions had IC50 of 29.3 ± 3.15 μg/ml, while 24-methylenecycloartan-3β-ol was not active.