Chlorogenic acids reactions

Sundower Seed. Compared to the FAO/WHO/UNU recommendations for essential amino acids, sunflower proteins are low in lysine, leucine, and threonine for 2 to 5-year-olds but meet all the requirements for adults (see Table 3). There are no principal antinutritional factors known to exist in raw sunflower seed (35). However, moist heat treatment increases the growth rate of rats, thereby suggesting the presence of heat-sensitive material responsible for growth inhibitions in raw meal (72). Oxidation of chlorogenic acid may involve reaction with the S-amino group of lysine, thus further reducing the amount of available lysine. 

R. K. Sharma, T. S. Fisher, and M. R. Hajaligol, Effect of reaction conditions on pyrolysis of chlorogenic acid, J. Anal. Appl. Pyrolysis 62, 281-296 (2002). 

According to the theory of free radical oxidation, antioxidizing activities of chlorogenic acids are stipulated by their participation in reaction with free radicals. Chlorogenic and caffeic acids have high stoichiometric numbers and reactivity with peroxyl radicals as compared with trolox, the water-soluble analogue of tocopherol [48]. Considering... 

A free radical scavenger will come to possess an unpaired electron once it has contributed an electron to neutralize a free radical. Paradoxically, the free radical scavenger becomes a free radical. When chlorogenic acids neutralize a free radical they become phenoxyl radicals. However, products of chlorogenic and caffeic acids formed by reaction with free radicals are rapidly broken down further to products that are not able to generate any free radicals. This is the beneficial nature of antioxidants, because other antioxidants are not necessary for the reduction of one-electron oxidation products of these compounds [39],... 

The other important property affecting lipid oxidation is the chelating effect of chlorogenic acids. It is important to keep in mind that the influence of biometals (Fe, Cu etc.) on lipid free radical oxidation is essential. It is well known that iron can react with hydrogen peroxide by the Fenton reaction (Equation 3). The hydroxyl radical formed in the Fenton reaction is capable of reacting with lipid and PUFA as the initiation stage. Iron can also participate in alkyl peroxide or lipid peroxide decomposition. Therefore, the nature of iron chelation in a biological system is an important aspect in disease prevention. 

Chlorogenic and caffeic acids have suppressed the formation of hydroxyl radical via the Fenton reaction, probably due to chelation of these acids with iron [44], Indeed, recent studies report that chlorogenic acid shows chelating activity or reducing activity on iron required for the production of superoxide and hydroxyl radicals, resulting in the inhibition of lipid peroxidation induced Fenton reaction [45, 63],... 

Chlorogenic acids are shown to have some desirable biological activities. Most of their property relates to their function as antioxidants, evidenced by their activity to scavenge free radicals, to inhibit the formation of free radicals, and to block the oxidation reaction. However, other activities based on mechanisms other than scavenging capacity cannot be ignored. Also, further tests for the in vivo bioactivity of chlorogenic acids are to be needed. However, it is expected that chlorogenic acids may be beneficial to human health. 

Caffeine (Fig. 11.3), widely used by humans as a stimulatory drug, has so far been detected only in a few plant species. The biological roles of caffeine are believed to be in defense against herbivory or as an allelopathic response to potential competitors.83 Caffeine is derived from the purine alkaloid xanthosine. From xanthosine, three methylations are necessary to produce caffeine. First, xanthosine is methylated on N7 by 7-methylxanthosine synthase (MXS or 7NMT) to produce 7-methylxanthosine, which is enzymatically hydrolyzed to produce 7-methylxanthine and ribose.85,86 The methylations of N1 and N3 of 7-methylxanthine to produce 1,3,7-trimethylxanthine (caffeine) occur in young leaves of tea, and the same enzyme, caffeine synthase, apparently catalyzes both reactions.55 In coffee plants, caffeine is mainly found in the beans but also occurs in the leaves. Caffeine is stored in the vacuoles of coffee leaves as a complex with polyphenols such as chlorogenic acid.87 In contrast to tea, coffee plants appear to have separate enzymes for each step of N-methylation.57... 

The electron transfer reactions between sulfur-sulfur three-electron-bonded complexes derived from methionine and four hydroxycirmamic acid (HCA) derivatives (caffeic acid, ferulic acid, sinapic acid, and chlorogenic acid) were studied by pulse radiolysis with spectrophoto-metric detection. These HCA derivatives are widely distributed... 

The enzymatic treatment of chitosan in the presence of tyrosinase and phenol derivatives produced new materials based on chitosan.91 During the reaction, unstable o-quinones were formed, followed by the reaction with the amino group of chitosan to give the modified chitosan. The tyrosinase-catalyzed modification of chitosan with phenols dramatically altered rheological and surface properties of chitosan. The modification with chlorogenic acid onto chitosan conferred the water solubility of chitosan under basic conditions.92 A new water-resistant adhesive was developed by the tyrosinase-catalyzed reaction of 3,4-dihydroxyphenethylamine and chitosan.93 Poly(4-hydroxystyrene) was modified with aniline by using tyrosinase catalyst.94 The incorporated ratio of aniline into the polymer was very low (1.3%). 

In plant and animal cells, many enzymes are compartmentalized, and several are also immobilized, greatly slowing down reactions. After the cells have been mechanically damaged, some reactions may proceed fast. A well-known example is the rapid enzymatic browning of apple tissue after the apple has been cut here, the cutting allows an enzyme, polyphenoloxidase, to reach its substrate, mainly chlorogenic acid. 

Guyot et al. (1998) studied the inhibitory activity of 5-caffeoylquinic acid, the main component of the chlorogenic acids (see Section 2.1.4) on the formation of alkylpyrazines in Maillard reactions with model systems valine or leucine and saccharose. Applying their results to green robustas, they concluded that the aroma quality increased when the chlorogenic-acids content decreased and when the sucrose content increased. 

Reeve, R. M. (1968). Histochemical differentiation between tyrosine and chlorogenic acid in plant tissues Nitrous acid reactions and metal chelation of nitrosotyrosine. J. Histochem. Cytochem. 16, 191-198. 

The second reaction has nothing to do with polyphenoloxidase. Potatoes contain a small amount of iron, which they absorb from the soil in an ionic form known as ferrous iron. Chlorogenic acid forms a colorless chemical complex with ferrous ion. When a potato is cut or cooked, the ferrous ion reacts with oxygen and converts to a form called ferric iron. The ferric-iron/chlorogenic-acid complex is black, and it causes the blue-black spots you often see in cooked potatoes. 

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