Bate-Smith reaction

Heating a procyanidin solution in a strong inorganic acid medium (HCl) in the presence of oxygen produces red cyanidin. This is known as the Bate-Smith reaction (1954) and was reported in the... 

Quantitation of total tannin concentration is still carried out by methods based on the classic Bate-Smith reaction heating in strong acid medium leads to the formation of carbocations, which in an oxidant medium forms cyanidin (an anthocyanin). The reaction mixture thus turns red (hence the old name... 

Ellagic acid concentration can be determined through an oxidation reaction with nitrous acid, and two methods have been described by Bate-Smith (1977) and by Wilson and Hagerman (1990), respectively. 

Wilson and Hagerman (1990) described an alternative spectrophoto metric procedure to quantify ellagic acid. This method has three advantages over the procedure developed by Bate-Smith (1977) 1) it is not sensitive to gallic acid, which can result in an overestimate of the ellagitannin content, 2) it is more sensitive, and 3) it is more convenient because oxygen does not interfere with the reaction. 

As it happens, the catechins and leuco-anthocyanins can be differentiated from other known tannin-like substances in that they give a red color-reaction with vanillin and concentrated hydrochloric acid (c/. Bate-Smith and Swain, 1953a). Although at present employed only as a qualitative test for their detection, this reaction might well serve as a basis for their quantitative estimation, since it depends on the 5,7-dihydroxy- substitution of the A ring, which is common to all the known... 

The term tannins also attributed to proanthocyanidins (condensed tannins) was defined by Bate-Smith and Swain in 1962 as water soluble phenolic compounds having molecular weights between 500 and 3,000 Da and, besides giving the usual phenolic reactions, they have special properties such as the ability to precipitate alkaloids, gelatine and other proteins. Tannins have been widely employed in the tanning process converting hide collagen in leather [292]. 

Actually there are no good definitions of alkaloids (Bate-Smith and Swain, 1966) since each one is either too narrow or too broad. Even in the restricted Winterstein and Trier definition, at least five alkaloid families exist that can be derived from different amino acids consequently, there is a need to establish the proper biosynthetic pathways to permit the application of the alkaloid character to chemotaxonomy, It has been mentioned above that canadine (berberidine) may be found in plants of six partially unrelated botanical families. This fact is not surprising when considered in relation to the biochemical investigations of canadine biosynthesis. Many reactions are necessary to convert tyrosine into canadine consequently, one might even wonder why the distribution of this alkaloid is so limited. In contrast, other plants (and even some that produce canadine) can produce many alkaloids that are derived from tyrosine but have a marked difference in structure. Tyrosine serves as the key precursor of alkaloids of the isoquinoline type, but other types of alkaloids, such as colchicine and the Amaryllidaceae and the Erythrina alkaloids, may be synthesized from this amino acid. The nucleus of an alkaloid molecule can arise from different precursors thus the indole nucleus in Erythrina alkaloids arises from tyrosine, while in brucine it comes from tryptophan (Figure 1.5). The alkaloids cinchonamine and cinchonine differ in that cinchonamine has an indole nucleus, while cinchonine (like quinine) has a quinoline nucleus however, they exist in a precursor-product relationship (that is, the quinoline type is derived from the indole type in a one-step reaction). 

Hexahydroxydiphenic acid in a bound form (3) is readily detected in a plant extract by an old but very distinctive color test - the Procter-Paessler reaction. Esters of type 3 react with nitrous acid to give a carmine or rose red, changing to brown-green, then purple, and finally indigo blue. The chemical basis of this reaction has not been discussed but it has been employed by Bate-Smith (6, 7) for the quantitative determination of 3 in plant extracts, and it forms the basis of a very useful spray reagent for the detection of 3 by paper chromatography (6, 7, 43). 

Figure Bl.7.12. A schematic diagram of a typical selected-ion flow (SIFT) apparatus. (Smith D and Adams N G 1988 The selected ion flow tube (SIFT) studies of ion-neutral reactions Advances in Atomic and Molecular Physics vol 24, ed D Bates and B Bederson p 4. Copyright Academic Press, Inc. Reproduced with pennission.)...

It was suggested by first Smith and Adams (1978) and then Huntress and Mitchell (1979) that radiative association reactions involving the methyl ion CH (synthesized via Reaction 3.20) and a host of small neutral species could lead to a variety of more complex ion precursors to organic molecules. The rate coefficients of these radiative association reactions have since been calculated by Bates (1983) and Herbst (1980a, b 1985 a, c). Let us consider some of these reactions and the subsequent dissociative recombination reactions ... 

A potentially important question in association reactions is the temperature dependence of the collisional stabilization step. While this dependence is usually small, it is not always negligible. The primary evidence for this temperature dependence is that results obtained with different buffers show appreciably different temperature dependences. This problem has received considerable theoretical attention (Bates 1979a Bohringer et al. 1983 Herbst 1982 Moet-Ner 1979 Patrick and Golden 1985 Smith et al. 1984 Viggiano 1986 Viggiano et al. 1985). 

Molecular ions are efficiently destroyed in reactions of dissociative recombination with electrons and negative ions. These processes are especially fast at low temperatures, with typical rates of about 10-7cm-3 s-1 at 10 K and negative temperature dependence, fl —0.5 (Woodall et al. 2007). For nearly all observed species, dissociative recombination is an important formation pathway (e.g. water and hydrocarbons). Often, at later evolutionary times, > 105 years, dissociative recombination is balanced by protonation reactions, e.g. CO + H+ -> HCO+ + H2 followed by HCO+ + e - CO + H. Dissociative recombination rates are not difficult to derive but branching ratios and products are not easily predictable (e.g. Bates Herbst 1988 Spanel Smith 1994). 

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