Simple organic acids

This section is mainly concerned with the non-volatile, non-nitrogen-containing organic acids. It is restricted to the aliphatic acids and alicyclic acids (except for fatty acids, which are covered in Sect. 6.4.2) the aromatic acids, except for shikimic and quinic acid, are covered in Chap. 7. Since only a limited number of acids have been reported to occur in woody tissues such as bark and heartwood, the acids present in other parts, such as leaves and fruit, are also included. Those found only in herbs are excluded. No attempt has been made to search all the woody plants for the occurrence of these compounds. In the following, a brief introductory explanation about the bioformation and function in plants is described for the respective organic acids (10, 33, 43, 61, 120, 121), and this is followed by tables listing the occurrence of the acid in woody plants, if any. 

The tricarboxylic acid (TCA) cycle is an essential metabolic pathway in plants. This cycle is amphibolic and functions not only in catabolism to supply energy as ATP, but also to generate precursors for anabolic pathways. Certain intermediates of the cycle, particularly a-ketoglutaric acid and oxaloacetic acid, are utilized 

Helinus ovatus Citrus sinnensis Couroupita guianensis Olea europaea Pyrus malus Rubus fruticosus Citrus sinnensis Camellia sinnensis Phyllanthus simplex Albizzia lebbeck 

Bauhinia purpurea Pyrus malus Citrus sinnensis Acer saccharum Nandina domestica Eucommia ulmoides Prunus cerasus Vitis vinifera Bauhinia purpurea Albizzia lebbeck 

Pyrus malus Cornus mas Albizzia lebbeck Bauhinia purpurea Prunus domestica Pyrus malus Ribes sp. 

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If RCOOH is a comparatively simple organic acid and R OH a monohydric alcohol then the enzyme is called an esterase. Examples of such esters are ethyl butyrate, C3H7COOC2H5, and ethyl mandelate, CeHjCH(OH)COOC2Hj. 

Nickel Salts and Chelates. Nickel salts of simple organic acids can be prepared by reaction of the organic acid and nickel carbonate of nickel hydroxide reaction of the acid and a water solution of a simple nickel salt and, in some cases, reaction of the acid and fine nickel powder or black nickel oxide. 

This is a copolymer consisting of hydroxybutyrate and hydroxyvalerate units incorporated randomly along the chain. The hydroxyvalerate content may be varied by adding controlled amounts of a simple organic acid. 

Aliphatic compounds Several water-soluble simple organic acids and alcohols are cannon plant and soil constituents. They include methanol, ethanol, n-propanol and butanol (40), and crotonic, oxalic, formic, butyric, lactic, acetic and succinic acids (41, 42), all of which inhibit seed germination or plant growth. Under aerobic conditions, however, aliphalic acids are metabolized in the soil and therefore, should not be considered a major source of allelopathic activity (40). 

Ali, M.A. Dzomback, D.A. (1996a) Competitive sorption of simple organic acids and sulfate on goethite. Environ. Sci. Techn. 30 1061-1071... 

Ali, M.A. Dzombak, D.A. (1996b) Effects of simple organic acids on sorption of and on goethite. Geochim. Cosmochim. 

Salicylic acid is a simple organic acid with a pKa of 3.0. Aspirin (acetylsalicylic acid ASA) has a pKa of 3.5 (see Table 1-3). The salicylates are rapidly absorbed from the stomach and upper small intestine yielding a peak plasma salicylate level within 1-2 hours. Aspirin is absorbed as such and is rapidly hydrolyzed (serum half-life 15 minutes) to acetic acid and salicylate by esterases in tissue and blood (Figure 36-3). Salicylate is nonlinearly bound to albumin. Alkalinization of the urine increases the rate of excretion of free salicylate and its water-soluble conjugates. 

Balistrieri, L. S., and J. W. Murray, The influence of the major ions of seawater on the adsorption of simple organic acids by goethite , Geochim. Cosmochim. Acta, 51, 1151-1160 (1987). 

Ushio, K., Ebara, K. and Yamashita, T. Selective inhibition of R-enzymes by simple organic acids in yeast-catalysed reduction of ethyl 3-oxobutanoate. Enzyme Microb. Technol. 1991,13 834-839. 

Dissolved organic matter dissolved (usually less than 0.45 or 0.2 xm) organic compounds that range from macromolecules to low molecular weight compounds (e.g., simple organic acids). 

The results of this first step have been successful, so the behavior of simple organic acids can be understood via a combination of spectroscopy and computational chemistry. Steps 2 through 4 are in the initial stages and will require extensive effort before reaching the same level of confidence as the ab initio results. 

Schoonen MAA, Xu Y, Bebie J. Energetics and kinetics of the prebiotic synthesis of simple organic acids and amino acids with the FeS-H2S/FeS2 redox couple as reductant. Orig. Life Evol. Biosph. 1999 29 5-32. 

INDIRECT UV DETECTION METHOD FOR ANALYSIS OF SIMPLE ORGANIC ACIDS... 

Fig.. . 12. Separation of a range of simple organic acids. Separation conditions 27 cm x 75 pm,. 5.0 s injeaion, 0.5 mM TTAB-5.0 mM phthalate-50 mM MES. pH 5.2.. 50°C, -.5 kV. Reproduced with permission from [19].

In other cases a wide variety of products, ranging from simple organic acids such as formic and oxalic acid to totally reduced CO2 in the form of carbon black, have been obtained by reduction of CO2 by an appropriate alkali metal amalgam [117]. 

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