Acetylcholinesterase Inhibitory Activity of Alkaloids Isolated from Stephania venosa.

Stephania venosa (Blume) Spreng or "Sa-Bu-Leud" is a Thai medicinal plant used for treatment of cancer and diabetes, and as a blood-tonic and aphrodisiac. This plant .ontains alkaloids as its major components and has been of interest for its acetylcholinesterase (AChE) inhibitory activity. Phytochemical screening - of S. venosa was made using HPLC analysis and showed the chemical variation between the same species from different provenances. Fractionation of .S..venosa extract yielded three alkaloids, namely, dicentrine, crebanine, and tetrahydropalmatine. AChE inhibitory potential of the isolated alkaloids was evaluated using Ellman's AChE inhibition assay. Dicentrine, crebanine, and tetrahydropalmatine inhibited-AChE activity with IC(50) values of 93.5, 86.6, and 168.6 μg/mL, respectively. The AChE inhibitory activity of the tertiary protoberberine alkaloid, tetrahydropalriiatine, was lower than that of the aporphine alkaloids, dicentrine and crebanine, whereas the quaternary protoberberine alkaloid, berberine, showed a higher AChE inhibitory effect than the others.