Identification of Acetylcholinesterase Inhibitors from Seeds of Plants of Genus Peganum by Thin-Layer Chromatography-Bioautography

In traditional Chinese medicine, plants of the genus Peganum have been used to treat cough, hypertension, diabetes, asthma, jaundice, lumbago, and many other ailments. In this study, seeds of the plants of genus Peganum, including P. harmala Linn., P. multisectum (Maxim) Bohr, P. nigellastrum Bunge, and Peganum variety were collected from different provinces in China. A simple, rapid, and effective thin-layer chromatographic (TLC) fingerprint combined with bioautographic technique has been established for the identification of acetylcholinesterase (AChE) inhibitors from these seeds. The methanol extracts of seeds were separated on silica gel plates with ethyl acetate-methanol-ammonia 10:1.5:0.5 (v/v) as mobile phase, and then the plates were inspected under UV 366 nm and visualized by spraying with both Dragendorff's and vanillin-sulfuric acid reagents as well as by bioautographic assay. Moreover, the limits on AChE inhibitive activity of harmine and harmaline were found to be 0.01 mu g, in comparison to that of galanthamine of also 0.01 mu g. The TLC fingerprints combined with the bioautographic method could distinguish the seeds of the different species of genus Peganum investigated. Moreover, harmine and harmaline displayed similar AChE inhibition compared to galanthamine.