EFFECTS OF THE METHANOLIC EXTRACT AND VINCOSAMIDE ISOLATED FROM THE LEAVES OF PSYCHOTRIA LEIOCARPA IN ANTICHOLINESTERASIC ACTIVITY
Introduction: Alzheimer's disease (AD) is the most common neurodegenerative
disease and the most prevalent cause of dementia. The cholinergic hypothesis
indicates the degeneration of cholinergic neurons and the reduction in the
concentration of the neurotransmitter acetylcholine (ACh) contribute significantly to
the cognitive decline associated with AD. Enzymatic inhibition of
acetylcholinesterase (AChE) is an important target for the treatment of Alzheimer's
disease (AD) and AChE inhibitors from plants, such as galantamine, are used for its
treatment. Our research group has works with species of the genus Psychotria,
which sed in folk medicine to treat various diseases and this is due to the presence
of indole alkaloids in the leaves. Objectives: Investigate the activity of “in vivo”
acetylcholinesterase of methanol extract and vincosamine (indole alkaloid) isolated
from the leaves of P. leiocarpa. Material and Methods: Methanolic extract (ME-PL)
prepared by thorough maceration, fractionated by chromatography column on silica
gel and the compound (PL-1) isolated on preparative thin layer chromatography.
NMR, leading to the identification of the vincosamine alkaloid, analyzed PL-1.The
AChE activity was measured according to the spectrophotometric method previously
described (Ellman, 1961)1 using male Wistar rats, previously treated by gavage
seven days with ME-PL (100 and 300 mg/kg); PL-1 (30 mg/kg) and control (0.9%
saline). On the last day of the experiments, 60 min after last dose the samples the
animals killed by decapitation and collected brain structures (cortex, hippocampus,
hypothalamus and striatum). The protein concentration of the homogenized
samples was determined by the Coomassie blue method (Bradford, 1976)2
Results: ME-PL (300 and 100 mg/kg) and PL-1 (30 mg/kg) demonstrated
acetylcholinesterase inhibitory activity significantly decreased in the cerebral
cortex, 47 ± 3%, 44 ± 1%, and 36 ± 1%. In the hippocampus, the level of inhibition
also observed: ME-PL 300 mg/kg = 32 ± 4%, 100 mg/kg = 31 ± 3% and 30 mg/kg =
28 ± 3% = of PL-1. In addition, in the hypothalamus the significant inhibition was 13
± 1%, 12 ± 1% and 14 ± 2% at doses of 300 and 100 mg/kg (ME-PL) and 30 mg/kg
(PL-1), respectively, compared to the control group. Discussion on Conclusion:
Based on this work, we can suggest that ME-PL and PL-1 (vincosamide) can be
strategies to increase the ACh to synanaptic enhance cholinergic transmission in the
brain for the treatment or some symptoms of the disease.
UFGD, Fundect e CNPQ.
Ellman, G. L. A new and rapid colorimetric determination of acetylcholinesterase
activity. Biochemical Pharmacology. 7 ed., p. 88-95. 1961.
Bradford, M.M. A rapid and sensitive method for the quantitation of microgram
quantities of protein utilizing the principle of protein-dye binding. Analytical
Biochemistry. 72ed. p. 248–254. 1976.
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