Qualitative determination of false-positive effects in the acetylcholinesterase assay using thin layer chromatography.
A method has been developed to determine the false-positive effects on acetylcholinesterase inhibition in the TLC assay based on Ellman's method. Various aldehydes and amines have been tested in order to determine whether the observed inhibition is due to a true enzyme inhibition or due to the inhibition of the reaction between thiocholine and 5,5'-dithiobis-(2-nitrobenzoic acid). 4-Dimethylaminobenzaldehyde, 3-ethoxy-4-hydroxybenzaldehyde, diethylamine, triethylamine, triethanolamine and tyramine showed real enzyme inhibition, although their activity was about 10(3) times lower than that shown by galanthamine. Heptanal, decanal, cinnamaldehyde, anisaldehyde, benzaldehyde, hexylamine and tryptamine appeared to show a non-specific chemical inhibition. By checking this chemical inhibition on the TLC assay, the true enzyme inhibition could be distinguished from the false-positive chemical inhibition observed in the toluene extract of Nerine bowdenii in the course of isolation of active compounds.
Rhee
In K
IK
Division of Pharmacognosy, Leiden/Amsterdam Center for Drug Research, Gorlaeus Laboratories, Leiden University, PO Box 9502, 2300 RA, Leiden, The Netherlands.
van Rijn
Richard M
RM
Verpoorte
Robert
R
D000110:Acetylcholinesterase / Q000378:metabolism*; D000447:Aldehydes / Q000032:analysis; D000588:Amines / Q000032:analysis; D002800:Cholinesterase Inhibitors / Q000032:analysis*; D002855:Chromatography, Thin Layer / Q000379:methods*; D005189:False Positive Reactions; D019668:Liliaceae / Q000737:chemistry; D012680:Sensitivity and Specificity
D000447:Aldehydes; D000588:Amines; D002800:Cholinesterase Inhibitors; D000110:Acetylcholinesterase