Phenols and Phenolic Acids

Endogenous or exogenous aromatic compounds such as phenols and phenolic acids react extremely rapidly with OH radicals to form a mixture of hydroxylated products (Halliwell et /., 1988). Indeed, aromatic hydroxylation serves as an efiective method for evaluating OH radical activity both in vitro (Moorhouse et al., 1985 Grootveld and Halliwell, 1986a) and in vivo (Grootveld and Halliwell, 1986b). 

Total Phenolics and Phenolic Acids in Plants and Soils 155... 

Table 1 Total phenolics and phenolic acids content (pg/g) in dry Rubus hirtus leaves determined by two different methods...

EXTRACTION AND DETECTION OF TOTAL PHENOLICS AND PHENOLIC ACIDS IN PLANTS... 

T22. Tompsett, S. L., A study of the identification and determination of phenols and phenolic acids in urine. CUn. Chim. Acta S, 149 (1958). 

Phenolics and their functional derivatives are widely found throughout the plant kingdom. One defining characteristic of these compounds is that their aromatic ring usually contains at least one hydroxyl substituent. In a broad sense, phenolics, which are classified according to their structural skeleton, are basically derivatives from simple phenols and phenolic acids, phenylpropanoids including coumarins and lignans, flavonoids and related compounds, and stilbenes. Some of these compounds which show anti-inflammatory activity are reviewed in this section. 

Chamberlain, W.J., M.E. Snook, D.B. Walters, and R.L. Stedman Isolation of phenols and phenolic acids from cigarette smoke condensate 30th Tobacco Chemists Research Conference, Program Booklet and Abstracts, Vol. 30, Paper No. 39, 1976 p. 28. 

Luthria, D.L., Mukhopadhyay, S., and Krizek, D.T., Content of total phenolics and phenolic acids in tomato (Lycopersicon esculentum Mill.) fruits as influenced by cultivar and solar UV radiation. J. Food Comp. Anal, 19, 771-777, 2006. 

A wide variety of stationary phases have been used to separate substituted monocyclic phenols and phenolic acid compounds and their derivates by thin-layer chromatography (TLC). In particular, the composition of phenolic acids and flavonoids in leaves, roots, and fruits of several plants and in natural products has been extensively studied by the two-dimensional TLC by using cellulose or silica gel plates in one direction and silanized silica gel in the second direction. Quantitative determinations of flavonoids components of plant extracts were widely performed. 

Van Sumere CF (1989) Phenols and phenolic acids. In Harbome JB (ed) Methods in plant biochemistry, vol 1, Plant phenolics. Academic, London, pp 29-73... 

In this section the thin-layer chromatographic properties of phenolic compounds as revealed by their / /Values are given. The first part covers essentially the substituted derivatives of monocyclic phenols, the second part is concerned with phenolic acids (with their derivatives), and the final one with more complex phenolic compounds such as phenolic glycosides, flavonoids, anthocyanins, lignan derivatives, phenolic steroids, cannabinoids, and other types. Some overlap between subsections is inevitable, but this feature serves incidentally to interrelate the thin-layer chromatographic properties of phenolic compounds as a whole. The material in the last section has been dealt with in other monographs (1), and more emphasis has been placed in this review on substituted phenols and phenolic acids and their simple derivatives. 

Plant secondary metabolites may inhibit specific enzymes, either in plants or in other species such as fungi or animals. In some cases, this appears to be the sole mode of action of the metabolite, whereas in others, enzyme inhibition forms part of a suite of effects. It must be noted, however, that the specificity and in vivo biological relevance of some findings remains questionable. An example of this is the inhibition of a variety of enzymatic reactions, including plant hormone biosynthetic enzymes, catalase, maltase and phosphatase by phenolics and phenolic acids (Macias et al, 2007). 

Soil organic substances are also comprised of biochemical compounds, such as simple aliphatic and aromatic acids, phenols and phenolic acids, hydroxamate siderophores, sugar acids, and complex polymeric phenols, which are synthesized by living organisms. Biochemical compounds are common to all soils and natural waters and would be expected to play a dominant role in zones where microbial activity is intense. However, biochemical chelating agents normally have only a transitory existence in the pedosphere, and the amounts found at any one time represent a balance between synthesis and destruction by microorganisms (Stevenson 1967). The amount of potential chelate formers present in soils is normally low and variable (Stevenson and Fitch 1986). Table 1 lists examples of different environments and the various types of biochemical compounds present within them. 

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