Pharmacological characterization of orally active cholinesterase inhibitory activity of Prunus persica L. Batsch in rats

Prunus persica L. Batsch water extract (PPE) is a potent acetylcholinesterase (AChE) inhibitor screened for the treatment of Alzheimer's disease. The effects of oral administration of the PPE were examined with comparison of those of selective butyrylcholinesterase inhibitors of 9-amino-1,2,3,4-tetrahydroacridine hydrochloride (tacrine) and tetraidopropylpyrophosphoramide (iso-OMPA) and a selective AChE inhibitor, donepezil, on the cholinesterase activity in the brain and plasma of rats. After the sequential solvent fractionation of the methanol extract of P. persica L. Batsch, the highest inhibitory fraction was that of chloroform (75%). The concentration that was required for 50% enzyme inhibition (IC50 value) was 5.6 μg/mL for the chloroform fraction. Oral administration of PPE or tacrine caused a dose-dependent inhibition of brain and plasma cholinesterase activities. The ID50 values of these compounds for brain cholinesterase activity were 2.7 g/kg and 8.9 mg/kg, respectively. On the other hand, the ID50 values for plasma cholinesterase activity were 18.6 g/kg and 27.5 mg/kg, respectively. Thus, the ratios of the ID50 (plasma < brain) were 6.0 and 3.1, respectively. These results suggest that orally administered PPE satisfactorily penetrates into the brain and inhibits cholinesterase there and that PPE is a potent inhibitor of brain cholinesterase in comparison with plasma cholinesterase in vivo.