Thesis-Final 03 June 2011 pdf - Jacobs University

Background Chapter 2
Scientists such as Lampadius (1832), Robiquet and Boutron (1837), suspected the
presence and identity of volatile acids by smell and by simple intuition. 114 The early
isolation and identification of non-volatile crystalline members such as quinic acid
was facilitated by their crystallization. 115 Freudenberg in 1920 reported that the
enzyme tannase hydrolysed chlorogenic acid to equimolar quantities of caffeic and
quinic acid. 116 In 1932 Fischer and Dangschat concluded that chlorogenic acid was 3-
caffeoylquinic acid. 117 Under current IUPAC recommendations is now designated 5-
caffeoylquinic acid. 118 In 1950 Barnes announced that 5-CQA was not the only
component in the chlorogenic acid fraction, by the isolation from coffee beans of a
fraction called isochlorogenic acid. Barnes et al. were of the opinion that
isochlorogenic acid is isomeric with chlorogenic acid and that the caffeoyl group is
substituted on the 5-OH group of quinic acid. 119 Thus Bean and Corse point out that
an enchancement of conductance of a chlorogenic acid isomer in boric acid solution
can be due to either the presence of vicinal hydroxyls or to alpha hydroxyl carboxylic
acid groups. 120 Williams showed that the chlorogenic acid and other cinnamic acid
derivatives give two spots due to the separation of the cis- and trans-isomers. 121 Paper
chromatography of quinic acid has also led to the appearance of multiple spots,
attributable, in part at least, to the formation of the 3-1actone. 122 The observation by
Butler and Siegelman that caffeic acid (3,4-dihydroxycinnamic acid) is partially
oxidized to esculetin during paper chromatography points to another possible source
of artifact formation. 123
Cellulose columns, 124 thin layer chromatography 125 and electrophoresis 126 have also
been employed. Ion exchange chromatography on the conventional polystyrene resins
is unsuited for the fractionation of chlorogenic acids beacuse of poor recoveries.
Apparently the phenolic moiety is very strongly bound to the resin, and a certain
amount of irreversible adsorption occurs. These shortcomings can probably be
overcome by the use of modified cellulose ion exchange materials, e.g.,
diethylaminoethylcellulose and carboxymethylcellulose. Silica gel columns are
particularly well adapted for work with chlorogenic acids. Using dilute aqueous
sulfuric acid as the stationary phase and a chloroform-butanol mixture, in which the
butanol content was increased stepwise, Sondheimer separated the chlorogenic acids
into four distinct bands. 127 This procedure has yielded quantitative information on the
distribution patterns of the chlorogenic acids in different plants, and has also been
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