exploratory analysis of an archaic cinchona bark collection
A museum collection of Cinchona cortex samples (n = 117), from the period 1850–1950, were extracted with a mixture of chloroform-d1, methanol-d4, water-d2, and perchloric acid in the ratios 5:5:1:1. The extracts were directly analyzed using 1H NMR spectroscopy (600 MHz) and the spectra evaluated using principal component analysis (PCA) and total statistical correlation spectroscopy (STOCSY). A new method called STOCSY-CA, where CA stands for component analysis, are described and an analysis using this method are presented. It was found that the samples had a rather homogenous content of the well-known cinchona alkaloids quinine, cinchonine and cinchonidine without any apparent clustering. Signals from analogues were detected but not in substantial amounts. The main variation was related to the absolute amounts of extracted alkaloids, which was attributed to the evolution of the Cinchona tree cultivation during the period the samples were collected.
Planta Medica, 2012, Vol 78, Issue 17, p. 1885-1890