Determination of kinetic parameters and structure-activity relationships of ginsenosides as inhibitors of cyclin-dependent kinase 5/p25 using ultra-pressure liquid chromatography with triple quadrupole tandem mass spectrometry.

RATIONALE:Cyclin-dependent kinase 5 (cdk5) is a serine/threonine kinase that is reported to play an important role in the pathogenesis of Alzheimer's disease. Ginsenosides have beneficial effects on Alzheimer's disease in both in vivo and in vitro experiments, but the precise mechanisms are not yet entirely clear. METHODS:In the present study, an ultrahigh-pressure liquid chromatography (UPLC) and triple quadrupole mass spectrometry (TQMS) assay was developed to study the activities of cdk5 for the first time. RESULTS:The calibration curves showed a good linear behavior over the range 0.04 μM to 10 μM (y = 0.934x + 0.045, R(2) = 0.995) with product phosphorylated peptide (PKpTPKKAKKV). The screening results suggested that the inhibition activities of ginsenosides are related to their chemical structures. CONCLUSIONS:The developed UPLC/TQMS-based method for determination of an inhibitor of cdk5/p25 is sensitive and reliable. The effect of ginsenosides on Alzheimer's disease may be involved with the regulation of activities of cdk5/p25.