An LC-MS/MS method for the simultaneous determination of lycorine and galanthamine in rat plasma and its application to pharmacokinetic study of Lycoris radiata extract in rats

A rapid, sensitive, and selective liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of lycorine and galanthamine, two major constituents in Lycoris radiata extract, in rat plasma. Liquid-liquid extraction with ethyl ether was carried out using diphenhydramine as the internal standard. The two bioactive alkaloids were separated on a Zorbax SB-C18 reserved-phase column (150 mm × 4.6 mm, i.d., 5 μm) by gradient elution using a mobile phase consisting of methanol with 0.1% formic acid (A) and water with 0.1% formic acid (B) at a flow rate of 0.6 mL/min. All analytes showed good linearity over a wide concentration range (r (2)>0.99) and the lower limit of quantification was 3.00 ng/mL for each analyte. The average extraction recovery of the analytes from rat plasma was more than 82.15%, and the intra-day and inter-day accuracy and precision of the assay were less than 12.6%. The validated method was successfully applied to monitoring the concentrations and pharmacokinetic studies of two Amaryllidaceous alkaloids in rat plasma after an oral administration of Lycoris radiata extract.

High-performance liquid chromatographic method with UV photodiode-array, fluorescence and mass spectrometric detection for simultaneous determination of galantamine and its phase I metabolites in biological samples

Galantamine, an alkaloid isolated from the bulbs and flowers of Caucasian snowdrop (Galanthus woronowii, Amaryllidaceae) and related species, is employed in human medicine for the treatment of various neuromuscular and neurodegenerative diseases. After the administration, the products of oxidative biotransformation (O-desmethyl-galantamine, N-desmethyl-galantamine, galantamine-N-oxide) and chiral conversion (epigalantamine) are formed in various concentrations from parent compound. For the identification and determination of galantamine and its phase I metabolites in blood plasma and tissues, a new bioanalytical method based on a reversed-phase high-performance liquid chromatography with UV photodiode-array, fluorescence and mass spectrometric detection was developed, validated and applied to pharmacokinetic and biotransformation studies. Sample preparation included a homogenization of the rat tissues (liver, brain, hypophysis) in a phosphate buffer 0.05 mol/L pH 7.4. Plasma samples and tissue homogenates were purified using a mixed-mode solid-phase extraction (Waters Oasis MCX cartridges). Galantamine, its above-mentioned metabolites and the internal standard codeine were separated on a Discovery HS F5 column (Supelco, 150 mmx4.6 mm I.D., 5 microm) at flow rate of 1 mL/min using a linear gradient elution. UV photodiode-array and mass spectrometric detection were employed for the identification of individual galantamine metabolites in various biomatrices, the fluorescence detection (lambdaexcit=280 nm/lambdaemiss=310 nm) was chosen for the quantification of galantamine and its metabolites. The developed method was applicable in liver tissue in the range from 0.50 to 63.47 nmol/g of galantamine, from 0.32 to 41.42 nmol/g of O-desmethyl-galantamine, from 0.54 to 69.40 nmol/g of N-desmethyl-galantamine and from 0.70 to 89.03 nmol/g of epigalantamine. Limit of detection was found to be 0.04 nmol/g for galantamine, 0.19 nmol/g for O-desmethyl-galantamine, and 0.07 nmol/g for N-desmethyl-galantamine and epigalantamine.

Cholinergic challenge in Alzheimer patients and mild cognitive impairment differentially affects hippocampal activation--a pharmacological fMRI study

Pharmacological functional MRI (phMRI) examines the impact of pharmacologically induced neurochemical changes on brain function at a system level. The current phMRI study directly compared effects of cholinergic stimulation on brain function between patients with Alzheimer's disease and mild cognitive impairment, a disease stage preceding the development of Alzheimer's disease. Brain function during recognition of (un)familiar information was examined for changes after exposure to galantamine, a cholinesterase inhibitor used for treating memory deficits in Alzheimer's disease. Alzheimer patients [n = 18; age 74.5 years +/- 8.2; Mini-Mental State Examination (MMSE) 22.5 +/- 2.4] and patients with mild cognitive impairment (n = 28; mean age 73.6 +/- 7.5; MMSE 27.0 +/- 1.2) were scanned during face recognition under three different conditions: at baseline, and after acute (single dose) and prolonged exposure (5 days) to galantamine. Functional data were analysed in an event-related fashion. In both groups, acute exposure produced strong increases in brain activation (Z > 3.1). Prolonged exposure produced less strong effects that mainly involved decreases in activation (Z > 3.1). In mild cognitive impairment, acute exposure increased activation in posterior cingulate, left inferior parietal, and anterior temporal lobe. Prolonged exposure decreased activation in similar posterior cingulate areas, and in bilateral prefrontal areas. Effects were stronger for positive ('familiar') than for negative ('unfamiliar') decisions, indicating that the effect was specific to memory retrieval. In Alzheimer patients, acute exposure increased activation bilaterally in hippocampal areas, whereas prolonged exposure decreased activation in these areas. Effects were more pronounced for negative than for positive decisions, suggesting a preferential effect on memory encoding. Unique profiles of signal reactivity were found in a number of areas, including left inferior parietal lobe and left hippocampus proper. The reactivity of posterior cingulate and hippocampal structures to cholinergic challenge suggests a key role of the cholinergic system in the functional processes that lead to Alzheimer's disease. The differential response to cholinergic challenge in mild cognitive impairment and Alzheimer patients may reflect a difference in the functional status of the cholinergic system between both groups, which is in line with recent results showing a differential clinical response to cholinergic treatment.