Bioactive substance

Proteias are metabolized coatiauously by all living organisms, and are ia dyaamic equilibrium ia living cells (6,12). The role of amino acids ia proteia biosyathesis has beea described (2). Most of the amino acids absorbed through the digestioa of proteias are used to replace body proteias. The remaining portioa is metabolized iato various bioactive substances such as hormones and purine and pyrimidine nucleotides, (the precursors of DNA and RNA) or is consumed as an energy source (6,13). 

J) At position 1, an acidic side chain two or three carbons long should be present. The natural L-alanyl side chain reduces receptor binding but enhances in vivo activity by increasing access to the receptor and by retarding metaboHsm and excretion. The enantiomeric D-analogues retain considerable activity in contrast to other bioactive substances (17). 

The Mukaiyama condensation method was also utilized in the synthesis of several antibiotics and related bioactive substances. These syntheses include apramycin, using 4-azido-2,3,6-tri-(P-benzyl-4-deoxy-) -D-glucopyranosyl fluoride (prepared from the corresponding a-D-glucopyranosyl chloride by the AgF method ) avermectin B , using protected sugar derivatives of oleandrosyl fluoride (a-L-Ole-F) and 0-(a-L-01e)-(1 4)-a-L-0le-F (both... 

KITTS D D (1994) Bioactive substances in food identification and potential uses. Can J Physiol Pharmacol. 72 423-34. 

Fruifs and vegetables also contain ofher bioactive substances such as polyphenols (including well-known pigments anthocyanins, flavonols) and non-provitamin A carotenoids (mainly lycopene, lutein, and zeaxanthin) that may have protective effects on chronic diseases. Polyphenols and carotenoids are known to display antioxidant activities, counteracting oxidative alterations in cells. Besides these antioxidant properties, these colored bioactive substances may exert other actions on cell signaling and gene expression. 

Bioluminescence can be used for spedfic detection of separated bioactive compounds on layers (BioTLC) [46]. After development and drying the mobile phase by evaporation, the layer is coated with microorganisms by immersion of the plate. Single bioactive substances in multicomponent samples are located as zones of differing luminescence. The choice of the luminescent cells determines the specificity of detection. A specific example is the use of the marine bacterium Vibrio fischeri with the BioTLC format. The bioluminescence of the bacteria cells on the layer is reduced by toxic substances, which are detected as dark zones on a fluorescent background. BioTLC kits are available from ChromaDex, Inc. (Santa Ana, CA). 

Phytochemicals or phytonutrients are bioactive substances that can be found in foods derived from plants and are not essential for life the human body is not able to produce them. Recently, some of their characteristics, mainly their antioxidant capacity, have given rise to research related to their protective properties on health and the mechanisms of action involved. Flavonoids are a diverse group of phenolic phytochemicals (Fig. 6.1) that are natural pigments. One function of flavonoids is to protect plants from oxidative stress, such as ultraviolet rays, environmental pollution, and chemical substances. Other relevant biological roles of these pigments are discussed in other chapters of this book. 

J.P. Devlin and D.P. Devlin, High Throughput Screening The Discovery of Bioactive Substances, Marcel Dekker, New York, 1997. 

An important number of these substances have an industrial origin. Some of them, like the pesticides, arrive intentionally in the environment and their use and release should be theoretically controlled. However, many of them have not been purposely produced as bioactive substances but more as components or additives of certain materials. Their significant growth in the chemical industry has not only been produced as a consequence of the discovery of new active principles in the pharmaceutical or pesticide area, but also because of the expansion of new technologies (electronics, containers, textiles, plastics, resins, foams, etc.), that require the development of new materials and substances with particular features. Most of these substances enter or are discharged to water and air sources without regulated controls. Wastewater treatment plants (WWTPs) are often not yet adapted to completely remove them, and therefore these new compounds can be found to some extent in wastewater effluents as well as in soil and sludge. 

Binodal curves, 20 320-321 Bins concept, 70 32 Bioaccumulation, of herbicides, 73 310 Bioactive barrier, defined, 3 758t Bioactive fixation, 72 611 Bioactive food ingredients, 7 7 646 Bioactive nutritions, 7 7 645t Bioactive substances identifying, 77 646 safety of, 77 647 Bioactive zone, defined, 3 758t Bioadhesive agents, 9 48, 49 Bioadhesive drug delivery systems, 9 45... 

Nonerodible systems, 9 58 Nonessential amino acids, 2 600 Nonessential bioactive substances, efficacy of, 17 648... 

R. Torronen and K. Maatta, Bioactive substances and health benefits of strawberries. Acta Horticult. 567 (2002) 797-803. 

Kolb, A.J., Burke, J.W., and Mathis, G., Homogeneous, time-resolved fluorescence method for drug discovery, in High Throughput Screening, The Discovery of Bioactive Substances, Devlin, J.P., Ed., Marcel Dekker, New York, 1997, chap. 19. 

John Siddall had intense scientific interest in two areas covered in this book. The chemical structures of the new bioactive substances discussed in the first section reveal configurations in which biological activity and specificity are highly dependent on isomeric differentiation, an area of synthesis that he understood and avidly pursued. He also advocated more extensive use of... 

Somatostatin has a very brief half-life in serum and is not useful clinically. An 8-amino acid analogue with 2 D-amino acids substituted for the naturally occurring L-amino acids is more stable, and monthly injections of a depot form of this analogue (octreotide, Sandostatin LAR) have several uses. Long-acting octreotide is used to treat acromegaly, as described earlier. It is also used to counteract unpleasant effects caused by overproduction of secreted bioactive substances produced by neuroendocrine tumors, including hyperinsulinemia from insulinomas and secretions from carcinoid tumors that cause severe diarrhea. Octreotide may also control severe diarrhea associated with AIDS that has not responded to other treatments. 

In search of bioactive substances, researchers have directed their interest towards substances found in plants. Parts of plants which have been used in natural medicine have proved to be a rich source of bioactive compounds however, to make use of them, they have to be isolated and their properties deterrnined. Using selective techniques of extraction has resulted in obtaining concentrated preparations of bioactive substances. To achieve comprehensive knowledge of their properties, it was necessary to develop methods of isolation of individual components and testing these methods. This could be done with chromatographic techniques. Isolated compounds were tested in order to show which of them (and to what extent) are responsible for bioactivity of plant preparations from which they were obtained. Due to the fact that many of the substances have the opposite effect, it is frequently impossible to use extracts without isolating individual compounds. 

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