Citric acid biological activities

Carbonyl compounds are everywhere. Most biological molecules contain carbonyl groups, as do most pharmaceutical agents and many of the synthetic chemicals that touch our everyday lives. Citric acid, found in lemons and oranges acetaminophen, the active ingredient in many over-the-counter headache remedies and Dacron, the polyester material used in clothing, all contain different kinds of carbonyl groups. 

Biological activities of structures similar to mevalonate can be found in WOMBAT. The closest similar molecule is in series 1062, which is (according to the paper it was published in) a novel thiol-containing citric acid analog (Figure 10.8 [53]). It has a measured Ki value that can be compared to other molecules in the series. The figure in bold indicates the common pattern for the majority of compounds in this series. 

Lawrence, C.L., Botting, C.H., Antobus, R., and Coote, P.J. 2004. Evidence of a new role for the high-osmolarity glycerol mitogen-activated protein kinase pathway in yeast Regulating adaptation to citric acid stress. Molecular and Cellular Biology 24 3307-3323. 

Molecular dynamics simulations [69] of citric acid in water at room temperature do show intermolecular hydrogen bonds to the solvent molecules along the entire trajectory [54]. To observe a gauche/trans-transition (T3) within a time-frame of a few 100 ps, the simulation temperature has to be elevated. Computational studies including a molecular environment capable of forming hydrogen bonds clearly are more relevant than gas-phase calculations in the search for biologically active conformations. 

There are some classes of compounds present in seawater which have known biological activity but have received little attention. Compounds involved in chemical communication, especially halogenated compounds, will be discussed in other chapters. Other compounds of interest are those involved in the citric acid cycle, the major pathway of metabolism in almost all cells. Citric acid cycle intermediates and reactions are involved in the biosynthesis of most of the major metabolites, from amino acids and carbohydrates to long-chain fatty acids and porphyrins (Mahler and Cordes, 1971). The intermediates, such as succinic, fumaric, malic, oxaloacetic, citric, gly-oxylic, and oxoglutaric acids are present in almost all organisms and are certainly being produced in the sea. 

Substantial part of my scientific activity was devoted to physicochemical properties of aqueous solutions of citric add and various inoiganic citrates. They included formation of metal-mixed complexes, determinations of solubiUties, vapour pressures of water above citric acid and citrates solutions, densities, melting points, sound velocities and electrical conductances. Unquestionably, the industrial and biological importance of citric acid was the main motivation that more than 25 sdentific papers I pubhshed together with my coworkers on systems with citrate ions. Our results up to 1994,1 summarized in the review entitled Thermodynamic and Transport Properties of Aqueous Solutions of Hydroxycaiboxylic Acids. The current book came as a desire to enlarge the information about citric acid properties presented there, to incorporate some subjects which were entirely omitted (chemistry of citric acid and properties of inorganic citrate solutiorrs) and finally to include our and others new relevant results. 

Antibiotics are not the only extracellular products obtained in this way alcohol, citric acid, lactic acid, 1-lysine are typical smaU-molecule examples of extracellular products. For biological macromolecules, examples of extracellular products include proteins, such as tissue-type plasminogen activator, monoclonal antibodies (mAbs), such as immunoglobulins, proteases (enzymes which degrade proteins such as subtilisins), used in a variety of applications of food processing, industrial and household applications, and polysaccharides, such as xanthan gum. 

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