Quinic acid concentrations 358

The treatment and environment of green coffee beans affects the concentrations of both caffeoyl- and feruloyl quinic acids,52 and several decomposition products have been recognized. Some of these products, in this case from steam-treated green coffee beans, are given in Figure 5.53... 

Quinic acid 13a is esterified by reaction with methanol in presence of a catalytic quantity of concentrated sulphuric acid to give in quantitative yield the methyl ester 13b which is acetylated after with acetic anhydride in pyridine. 

Cloning of a cDNA encoding HCT from tobacco N. tabacum, NtHCT) stems and expression of the recombinant protein in fully functional form in E. coli as a fusion product have also been carried out, with kinetic parameters of the purified protein determined (C. L. Cardenas etal, manuscript in preparation). " The overall catalytic propenies of recombinant NtHCT with various hydroxycinnamoyl CoAs (9-13) using either shikimic (29) or quinic (28) acid as substrate were quite informative (C. L. Cardenas et al, manuscript in preparation). With shikimic acid (29) at a saturating concentration, the observed /feat/Am of recombinant NtHCT established that the dominant HCT activity was with -coumaroyl CoA (9) (114840mor ls ) over that of caffeoyl (10), feruloyl (11), or sinapoyl (13) CoA (48 420, 6880, and 420 moF 1 s , respectively). Recombinant NtHCT was able, however, to less efficiently transfer hydroxycinnamoyl moieties from -coumaroyl CoA (9) and caffeoyl CoA (10) to quinic acid (28). Indeed, /fcat/Am values at saturating concentration of quinic acid (28) were lower by approximately 7.5- and 131-fold for/)-coumaroyl CoA... 

Anthocyanin (cyanidin) pigmentation can be observed in some cultivars, although its nature has not been fully determined. 3 -Caffeoylquinic is the principal phenolic acid derivative, although 4 - and 5 -caffeoylquinic acids are also present. A concentration of 167 mg caffeic acid per kg has been reported in apricots [19]. The presence of the corresponding p-coumaroyl-and feruloyl quinic acid derivatives has also been reported [16], as have p-coumaroylglucose and feruloyl glucose. 

An HPLC study of the individual phenolic acid derivatives showed chlorogenic acid to be the predominant compound in potato (22-71 mg/kg). Cryptochlorogenic acid (11 mg/kg), neochlorogenic acid (7 mg/kg) and isochlorogenic acid (4,5-dicaffeoyl quinic acid) (Fig. 4) (3 mg/kg) were also present in smaller amounts [80]. It was also demonstrated that caffeic acid compounds are not distributed uniformly in the tuber, but occur in strongly decreasing concentrations from the outer to the inner section. About 50% of the compounds as a whole are located in the potato peel and adjoining tissue. 

Surveys of plants indicate that free shikimic acid occurs ubiquitously, albeit in low concentrations in most plants. Low concentrations are to be expected, however, since the compound is an intermediate in the synthesis of the aromatic amino acids. Quinic acid generally occurs in higher concentration than shikimate, particularly in woody plants (Yoshida, 1969, Yoshida et ai, 1975). Both acids occur in conjugates with phenolic acids such as cafifeoyl quinate (chlorogenic acid) (Haslam, 1974). 

With this huge amount of concentrations it is possible to detect frauds like the addition of sugar, exhaustive enzymatic treatment (galacturonic acid), addition of citric acid or lemon juice (e.g. in apple juice), extraction of orange peel (phlorin) or the usage unripe Suits (quinic acid in apple juice). 

Phenolic compounds are widely distributed in plant parts from the roots to the seeds and include phenolic acids, flavo-noids and tannins. The tannins may reduce protein digestibility (Ford and Hewitt, 1979) and perhaps the bioavailability of other nutrients. The flavonoids have been reported to have a number of nutritional and pharmacological activities (Kuhnau, 1976). Phenolic acids include benzoic and cinnamic acid derivatives. The benzoic acid derivatives include p-hydroxy-benzoic, protochate-chuic, vanillic, gallic and syringic acids. The cinnamic acids, p-coumaric, caffeic, ferulic and sinapic are found in most oilseeds used to prepare protein concentrates and frequently occur in the form of esters with quinic acid or sugars. Chlorogenic acid for example is an ester of caffeic acid and quinic acid and is found in several isomeric and derivatized forms. 

Stoll et al. [39] isolated echinacoside from the roots of Echinacea angustifolia. It is the major polar constituent and is present at a concentration of 0.3-1.7% [15, 31, 39-41]. It occurs in . pallida at a similar concentration and is therefore not suitable for the discrimination of these two species [42]. However, they can be distinguished by the occurrence of 1,3- and 1,5-O-dicaffeoyl-quinic acids (Fig. 3), which are only present in the roots of . angustifolia [31]. 

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