Measurement and pharmacokinetics of vincamine in rat blood and brain using microdialysis

In vitro characterization of transport and metabolism of the alkaloids: vincamine, vinpocetine and eburnamonine

PURPOSE

Vincamine, vinpocetine and eburnamonine are alkaloids known for their neuroprotective attributes, enhancement of cerebrovascular blood flow and antitumor effect of their derivatives. However, the relative metabolic stability of these alkaloids and their extrusion by the drug efflux transporters expressed at the blood-brain barrier (BBB) are not clear. In this study, we developed rapid and sensitive methods for the detection of these alkaloids and investigated their relative metabolic stability and their interaction with drug efflux transporters.

METHODS

UPLC methods were developed to analyze metabolic in vitro samples. Intrinsic clearance was determined using rat liver microsomal enzymes. Drug-stimulated transporter activity was estimated by measuring inorganic phosphate released from ATP spectrophotometrically.

RESULTS

The UPLC methods quantification level ranged from 0.02 to 0.025 µg/mL, indicating high sensitivity. The intrinsic clearance of eburnamonine was significantly less than both vincamine and vinpocetine. Different concentrations of the three drugs (4, 20 and 100 µM) induced minimal stimulation of the ATPase activity of the Bcrp and Pgp membrane transporters.

CONCLUSIONS

The developed simple, sensitive and reliable UPLC analysis methods can be utilized in future in vitro and in vivo studies. The three alkaloids demonstrated minimal interaction with the drug efflux transporters Pgp and Bcrp, concordant with the ability of these alkaloids to cross the BBB. The relative metabolic stability of eburnamonine compared to the other alkaloids suggests the use of eburnamonine or its derivatives as lead compounds for the development of antitumor and nootropic agents that need to cross the BBB and produce their pharmacological effects in the CNS.

Brain trace element concentration of rats treated with the plant alkaloid, vincamine

Trace elements are essential for normal brain functions. Tiny amounts of these elements help in the formation of neurotransmitters and involved in the antioxidant defense and intracellular redox regulation and modulation of neural cells. Vincamine is a plant alkaloid used clinically as a peripheral vasodilator that increases cerebral blood flow and oxygen and glucose utilization by neural tissue to combat the effect of aging. Neurodegenerative diseases associated with aging characterized by a disturbance in trace element levels in the brain. The objective of this study was to determine the level of zinc (Zn), copper (Cu), iron (Fe), Selenium (Se), and chromium (Cr) in the brain of rats treated with vincamine. Vincamine was injected i.m. to rats at a dose of 15 mg/Kg bodyweight daily for 14 days. Twenty-four hours after the last injection, rats were killed, and brains were ashed and digested by concentrated acids and analyzed for trace elements concentrations by flame emission atomic absorption spectrophotometer. The results showed that Zn was the highest trace element in the brain of control rats (3.134 +/- 0.072 ppm) and Cr was the lowest (0.386 +/- 0.027 ppm). Vincamine administration significantly (p < 0.01) reduced the brain Fe concentration (1.393 +/- 0.165 ppm) compared to control (2.807 +/- 0.165 ppm). It was concluded that Zn was the highest trace element in the brain of rats. Vincamine administration resulted in approximately 50% reduction in brain Fe concentration which suggests its beneficial effect to prevent the oxidative stress of Fe in neurodegenerative diseases such as Parkinson's, Alzheimer's, and Huntington's diseases.

Bioavailability and tissue distribution of sesamol in rat

Sesamol, generally regarded as the main antioxidative component in sesame oil, can be generated from sesamolin by roasting sesame seed or bleaching sesame oil. This paper reports the bioavailability of sesamol in Sprague-Dawley (SD) rats. Biological fluid was sampled following a dose of sesamol of 50 mg/kg by gastric gavage (p.o.) or by intravenous injection. The pharmacokinetic data of sesamol were calculated by noncompartmental model. The tissue distribution of sesamol (p.o., 100 mg/kg) in SD rats was also investigated. The concentration changes of sesamol were determined in various tissues and plasma within a 24 h period after oral administration of sesamol. The results showed that the oral bioavailability of sesamol was 35.5 +/- 8.5%. Sesamol was found to be able to penetrate the blood-brain barrier and go through hepatobiliary excretion. Sesamol conjugated metabolites were widely distributed in SD rat tissues, with the highest concentrations in the liver and kidneys and the lowest in the brain. It is postulated that sesamol is incorporated into the liver first and then transported to the other tissues (lung, kidneys, and brain). The major metabolites of sesamol distributed in the lung and kidney were glucuronide and sulfate.

Analysis of interaction property of bioactive components in Flos Lonicerae Japonicae with protein by microdialysis coupled with HPLC-DAD-MS

Interaction of the Flos Lonicerae Japonicae (FLJ) with protein was studied by microdialysis coupled with HPLC-DAD-MS. Eight compounds were identified by comparing their t(R), UV data and MS data with reference compounds. Microdialysis recoveries and binding degrees of compounds in FLJ with bovine serum albumin (BSA) were determined. Recoveries of microdialysis sampling ranged from 51.3 to 73.2% with relative standard deviation (RSD) below 3.1%, and the binding degrees of those compounds to BSA ranged from 4.8 to 61.2 (0.3 mM BSA) and from 11.1 to 76.2% (0.6 mM BSA), respectively. The results showed that the binding properties of compounds in FLJ were influenced by pH. Furthermore, the binding degrees of five reference compounds were determined separately under the same conditions, the binding degrees of chlorogenic acid, luteolin-3-O-glucoside and 4,5-di-O-caffeoyl quinic acid was lower in FLJ than in single compound solution, on the contrary the binding degree of caffeic acid and rutin was higher in FLJ, which indicated that a significant effects of the interaction of compounds with each other on their binding degrees to BSA. The results showed that there were ten compounds had interaction with BSA, eight of them were the proven active compounds, and the other two compounds had similar binding degree with the proven active compounds, so the ten compounds might possess potential activities.