Acids Synergism

Clavulanic acid has only weak antibacterial activity, but is a potent irreversible inhibitor for many clinically important P-lactamases (10—14,57,58) including penases, and Richmond-Sykes types 11, 111, IV, V, VI ([Bacteroides). Type I Cephases are poorly inhibited. Clavulanic acid synergizes the activity of many penicillins and cephalosporins against resistant strains. The chemistry (59—63), microbiology (64,65), stmcture activity relationships (10,13,60—62,66), biosynthesis (67—69), and mechanism of action (6,26,27,67) have been reviewed. 

Jaksic, A. et al., Cis-urocanic acid synergizes with histamine for increased PGE2 production by human keratinocytes Link to indomethacin-inhibitable UVB-induced immunosuppression, Photochem. Photobiol. 61, 303-309, 1995. 

McDowell, W. J., Case, G. N., McDonough, J. A., Bartsch, R. A., Selective extraction of cesium from acidic nitrate solutions with didodecylnaphthalene-sulfonic acid synergized with bis(tert-butylbenszo)-21-crown-7 Anal. Chem., 64, 3013-3017, 1992. 

When acid chelators are combined with one of the phenolic-type antioxidants, they can act synergistically. This type of synergism has been referred to as acid synergism (S). In this case, the primary role of a chelator is to bind metals, or metalloproteins that promote oxidation and thus, allow the antioxidant to perform its function and capture free radicals. In this manner, acid synergism is different than the BHA/BHT system. 

Ac-Phc-Lys-OH, enzymatic synthesis, 156f Acesulfame K, stnicture, 7f Acetoin, in reactions of aldehydes with ammonium sulfide, 36-54 Acid chelators, 57-58 Acid synergism, description, 58 Acidic amino acid peptides, taste,... 

Some chemically related compounds antagonize the action of auxins, for example, relieving the inhibition of root growth caused by 2,4-D. In contrast, 2,3,5-triiodbenzoic acid synergizes the action. 

Wilson EL and Reich E (1978). Plasminogen activator in chick fibroblasts induction of synthesis by retinoic acid synergism with viral transformation and phorbol ester. Cell, 15, 385-392. 

By way of comparison, we might consider the famesol/anacardic acid synergism against P. acnes. Its antibacterial activity against this follicular bacterium was significantly increased in combination with AMIC of anacardic acid isolated from the cashew Anacardium occidentale (Anacardiaceae) apple, nut and nut shell oil (32). More specifically, the MIC of famesol was lowered from 6.25 to 0.78 /tg/ml, in combination with 0.39 ftg/ml of anacardic acid. Interestingly, this synergism was found to be vice versa the MIC of anacardic acid was reduced from 0.78 to 0.2 /tg/ml when it was combined with 3.13 /tg/ml of famesol (33). The mode of action of the combination, however, remains unclear. 

Nasef, M.M., Saidi, H. and Dahlan, K.Z.M. 2010a. Acid synergized grafting of sodium styrene sulfonate onto electron beam irradiated poly(vinylidene fluoride) films for preparation of fuel cell membrane. 118 2801-2809. 

Comaglia-Ferraris P, Mariottini GL, Ponzoni M (1992) Gamma-interferon and retinoic acid synergize in inhibiting the growth of human neuroblastoma cells in nude mice. Cancer Lett 31 215-220... 

The corrosion of copper by carbonic acid deserves special attention. There is a synergism between oxygen and carbonic acid with regard to corrosion. Carbonic acid in the absence of oxygen is not corrosive to most copper alloys. However, corrosivity can be appreciable if oxygen is present. 

This is interesting when one considers the effect of synergists on the synthetics. All of the synthetics mentioned above are based on chrysanthemum monocarboxylic acid and in the case of allethrin, cyclethrin, and furethrin on the alcohol moiety there is only one double bond. When checked against the standard synergists, these synthetics do not show the degree of synergism shown by pyrethrins and this may be because of the fact that there is only one double bond for epoxidation, compared with two in the pyrethrolone radical, and therefore the synergist would not block this epoxidation step as effectively. 

Figure 45-6. Interaction and synergism between antioxidant systems operating in the lipid phase (membranes) of the cell and the aqueous phase (cytosol). (R-,free radical PUFA-00-, peroxyl free radical of polyunsaturated fatty acid in membrane phospholipid PUFA-OOH, hydroperoxy polyunsaturated fatty acid in membrane phospholipid released as hydroperoxy free fatty acid into cytosol by the action of phospholipase Aj PUFA-OH, hydroxy polyunsaturated fatty acid TocOH, vitamin E (a-tocopherol) TocO, free radical of a-tocopherol Se, selenium GSH, reduced glutathione GS-SG, oxidized glutathione, which is returned to the reduced state after reaction with NADPH catalyzed by glutathione reductase PUFA-H, polyunsaturated fatty acid.)...

The most common natural antioxidants are tocopherols, ascorbic acid and P-carotene (more often synthetic nature-identical compounds than natural products). Their changes were studied in detail in model systems, fats and oils, but experimental evidence is mainly lacking on more complicated systems, such as natural foods and ready dishes. Still less is known on different antioxidants from spices and from essential oils. These data will probably be obtained gradually. Very little is known about synergism of antioxidants in food products other than edible fats and oils or their regeneration from the respective free radicals and quinones. In mixtures, some antioxidants are preferentially destroyed and others are saved. Some data have already been published, but these complex changes should be studied in more detail. 

JiAZ s,ZHOU B, YANG L, wu L M and LIN z L (1998) Autioxidant synergism of tea polyphenols and a-tocopherol against free radical induced peroxidation of linoleic acid in solution, J Chem Soc Perkin Trans, II, 911-15. 

URBERG M, ZEMEL M B (1987) Evidence for synergism between chromium and nicotinic acid in the control of glucose tolerance in elderly humans. Metabolism, 36 896-9. 

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