Cinchona Bark - A Study in Alkaloids. – University of Copenhagen

Forward this page to a friend Resize Print Bookmark and Share

Department of Pharmacy > Research > Section of Analytical Biosciences > Drug Metabolism Lab > Cinchona Bark

 

Cinchona Bark - A Study in Alkaloids.

The aim of this project is to investigate the composition and quantity of Cinchona alkaloids of representatives of all genera of the tribe and of several samples of all species of Cinchona using chromatographic and spectroscopic techniques. While earlier projects has focused on the four main alkaloids we are also taking the minor alkaloids into account, including their potential as anti-malarias.

Relative activity of the four main alkaloids:

Alkaloid Rel. Mean plasma conc. Approx. daily dose (grams) Quinine equivalent
Quinine
Quinidine
Cinchonine
Cinchonidine
5.0
1.0
0.1*
2.5
0.50
0.25
1.00
1.00
1
2
½
½

*Relatively greater resistance of P. falciparum to cinchonine therapy

 

 

 

 

 

 

 

 

Figure 1. The four major alkaloid in Cinchona bark.

The first problem to be solved in sample preparation was an economically feasible way to grind small bark samples. To achieve this we modified a commercial coffe-grinder (eliminating a relatively large dead volume and optimizing the chute):

 

 

Figure 2. Comercial coffee grinder (conical burr grinder) modified for grinding samples.

 

This approach led to highly repeatable and low dispersion of grain size and to sufficiently repeatable extraction results. Most available equipment turned out to be milling machinery that would make highly repeatable grinding difficult (extraction depends on grain size).

An LC-MS method was developed based on an older LC-UV method. The highly improved method showed – due to increased resolution and sensitivity – a large number of unknown compounds that will be examined in relation to biological activity and importance for phylogenetic profiling. The current LC-MS method will therefore be optimised further.

The project is a part of the project: The Quest for Cinchona – A Phylogenetic Tale (PI Nina Rønsted, Natural History Museum of Denmark). This project is also linked to the project “Metabonomics in Drug Metabolism and Plant Medicine”.

Figure 3. Chromatograms of some samples of Cinchona bark (upper three traces) and a sample containing the four major alkaloids (lower trace). NB. Upper trace is fluorescence detection (Ex 330 nm, em 420 nm), lower three traces UV detection at 330 nm.

Instrumentation/analytical methods.
MS spectra are obtained at the LC-MS instruments of the Drug Metabolism group at the department of Pharmacy (e.g. the Thermo Exactive Orbitrap instrument).

NMR spectra are acquired at the Dedicated metabolomics and HPLC-SPE-NMR instrument at the Copenhagen Small-Molecule NMR Centre.