Phenolic cinnamic acid based

Figure 6.5 shows the structures of tra 5-cinnamic acid and four cinnamic acid derivatives (phenolic compounds) reported to be present in potatoes. Because potatoes are one of our major food plants, we validated with the aid of HPLC and LC/MS the content and distribution of antioxidative phenolic compounds in parts of the potato plant, in potato tubers, in the peel and flesh of tubers, in potatoes sold commercially in Korea and the United States, and in home-processed potatoes. The following discussion, based on our own studies, is followed by a brief overview of analytical methods for potato phenolic compounds by other investigators. 

Singleton and Esau (I) reviewed the methods for phenol analysis of wine. They pointed out that study would be greatly advanced if one could determine the total content of phenolic substances and express it in such a way that analysis of subclasses of phenols could be related to the original total and a balance sheet could be obtained. One could then say, for example, this wine has a total phenolic content of 1200 mg/liter calculated as gallic acid, and of that total, cinnamic acid derivatives account for 200 mg/liter, anthocyanins for 300 mg/liter, other small flavonoids for 200 mg/liter, and condensed tannins complete the total with 500 mg/liter of gallic acid equivalent. To accomplish this, the total phenol analysis not only must meet ordinary criteria of reproducibility and precision, but it also must be based on chemical relationships such that fractions determined separately can be converted to units of the total. Of course when clearcut fractionation can be accomplished by... 

Nonflavonoid compounds comprise simple phenols, phenolic acids, coumarins, xanthones, stilbenes, lignins, and lignans. Phenolic acids are further divided into benzoic acid derivatives, based on a C6-C1 skeleton and cinnamic acid derivatives, which are based on a C6-C3 skeleton [6], The conmarins are phenolic acid derivatives composed of a benzene ring fnsed with an oxygen heterocycle. Xanthones consist of a C6-C1-C6 basic structure, and stilbenes are composed of a C6-C2-C6 skeleton with various hydroxylation patterns [13], Lignins are polymers of C6-C3 units, whereas lignans are made up of two phenylpropane units [13]. The structures of each of these classes are shown in Table 16.1. 

There are several ways in which phenols have been categorized. Harbome and Simmonds categorized polyphenols based on the number of carbon atoms, which includes simple phenols (Ce) phenolic acids and related compounds (Ce—Ci) acetophenones and phenyl acetic acids (Cg—C2) cinnamic acids, cinamyl aldehydes, and alcohols (Cg—C3) coumarins, isocoumarins, and chromones (Cg—C3) flavonoids (C15) biflavonyls (C30) stilbenes (Cg—C2—Cg) benzophenones and xanthones (Cg—C2—Cg) quinones (Cg, Cio, Cm) betacyanins (Cjg) and lignans, lignins, tannins, and phlobaphenes (which are dimmers, oligomers, or polymers) [19]. Polyphenols have also been categorized by some researchers based on their... 

Phenohc acids are nonflavonoid polyphenolic compounds that mainly exist in two forms based on C1-C6 and C3-C6 backbones, benzoic and cinnamic acid derivatives, coimnonly known as hydroxycinnam-ic and hydroxybenzoic acids. Hydroxybenzoic acids (Figure 3.9) are found in a few plants consumed by humans, such as berries and onions [54], While vegetables and fhiits contain many free phenolic acids, in seeds and grains, particularly in the bran or hull, phenolic acids are... 

Fig. 2.7 The effects of pH on the ionic state of a theoretical phenolic acid with a pKa value of 4.5 (a) and estimated pKa values for cinnamic and benzoic acids (b). Where CAF equals caffeic acid, PCO equals p-coumaric acid, FER equals ferulic acid, SIN equals sinapic add, POH equals p-hydroxybenzoic acid, SYR equals syringic acid, and VAN equals vanillic add. A pKa value for caffeic acid was not available. Figure (b) based on data from Blum et al. (1999b). CRC Press LLC, data used with permission of Taylor Francis Ltd, http //www.tandf.co.uk/joumals. Origintil sources of data Al Leo, personal communication, Leo et al. (1971), Nordstrom and Lindbeig (1965), Kenttamaa et al. (1970), Connors and Lipari (1976) Glass (1975)...

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