Thesis-Final 03 June 2011 pdf - Jacobs University

Background Chapter 2
used in the isolation of chlorogenic acid and related compounds from unroasted coffee
beans. 128 A refinement of this method, employing a linear solvent gradient with
cyclohexane, t-butyl alcohol and chloroform, has been described by Hanson and
Zucker. 129 Zucker found out that there is danger of rearrangements because of transesterifications
during the isolation of the chlorogenic acids and this seems to be more
likely to occur with bases than under acidic conditions.
Titration experiments and infrared absorption spectra of isochlorogenic acid have
failed to support the claim for a mobile equilibrium between an open acid form and a
lactone. Also, evidence has become available that isochlorogenic acid, as purified by
the procedure of Barnes et al., is still heterogeneous and can be subdivided by
chromatographic techniques into several fractions. 130
Hanson reported optical rotatory dispersion (ORD) data for quinic acid and CiQA, but
the complex curves were not interpreted. 131 Gaffield reported and discussed ORD data
for quinic acid, quinide and several derivatives. The conformational implications were
consistent with the available NMR data. 132 Mass spectra for 3-CQA, 4-CQA, 5-CQA
and 1,5-diCQA have been published by Bombardelli and König and Sturm. 133,134 NMR
spectra of quinic acid and many derivatives including some lactones and chlorgenic
acids were reported extensively by Corse and his colleaques. 135,136,137 UV spectra of
various chlorogenic acids was reported by several authors. 138,139 Gas chromatograph
method for chlorogenic acids was published by Kung, Müller and Herman. 140,141
Hanson and Zucker applied low pressure column chromatography to the seperation of
chlorgenic acids. They used cyclohexane-chloroform (10:90) and t-butylalcoholchloroform
(10:30). 142 The earliest chlorogenic acid analyses by HPLC were
published by Court, Rees and Theaker. Van der Stegen and Van Duijn achieved a
separation of twelve chlorgenic and two cinnamic acids. 143,144,145 Later on this system
with minor variations was widely adopted. 146,147,148,149 Engelhardt et al. developed an
HPLC method that allowed the determination of mono and dicaffeoylquinic acids
along with corresponding lactones and ferruloylquinic acids, in roasted coffee in one
chromatographic run. The elution order was verified by isolation of individual
compounds by preperative HPLC, chromatography of the fractions on the analytical
HPLC system, NMR spectroscopy and thermospray LC-MS. 150
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