Malic acid Inactive

Inactive malonic, fumaric, and maleic acids from the active malic acid inactive succinic and tartronic acids from the active tartaric acid inactive cymene from active camphor, etc. 

Optically inactive starting materials can give optically active products only if they are treated with an optically active reagent or if the reaction is catalyzed by an optically active substance The best examples are found m biochemical processes Most bio chemical reactions are catalyzed by enzymes Enzymes are chiral and enantiomerically homogeneous they provide an asymmetric environment m which chemical reaction can take place Ordinarily enzyme catalyzed reactions occur with such a high level of stereo selectivity that one enantiomer of a substance is formed exclusively even when the sub strate is achiral The enzyme fumarase for example catalyzes hydration of the double bond of fumaric acid to malic acid m apples and other fruits Only the S enantiomer of malic acid is formed m this reaction... 

The optical activity of malic acid changes with dilution (8). The naturally occurring, levorotatory acid shows a most peculiar behavior in this respect a 34% solution at 20°C is optically inactive. Dilution results in increasing levo rotation, whereas more concentrated solutions show dextro rotation. The effects of dilution are explained by the postulation that an additional form, the epoxide (3), occurs in solution and that the direction of rotation of the normal (open-chain) and epoxide forms is reversed (8). Synthetic (racemic) R,.9-ma1ic acid can be resolved into the two enantiomers by crystallisation of its cinchonine salts. 

In Leuconostoc oenos ML 34, we have shown oxaloacetic acid decarboxylation manometrically (6, 7, 8). We were also able to demonstate fluorometrically the enzymatic production of reduced NAD with malic acid as a substrate, but, of course, were unable to do so with oxaloacetic acid since no NADH could be formed from this substrate. It is likely that this oxaloacetic acid decarboxylation activity, as in Lactobacillus plantarum, is distinct from the activity causing the malic-lactic transition. It is also possible that oxaloacetic acid decarboxylation is caused by a malic enzyme. However, there is no verified NAD dependent malic oxidoreductase (decarboxylating) enzyme which does so (12). For example, Macrae (31) isolated a malic enzyme from cauliflower bud mitochondria which showed no activity with oxaloacetic acid. Similarly, Saz (32) isolated a malic enzyme from Ascaris lumbricoides which is also inactive toward oxaloacetic acid. True, the Enzyme Commission (12) lists an enzyme described as L-malate NAD oxidoreductase (decarboxylating) (E.C. 1.1.1.38) which is said to be capable of decarboxylating oxaloacetic acid, but its description dates back to the studies of Ochoa and his group, and we now feel this listing may be improper. 

At the present time commercial malic acid is chiefly produced by the hydration of maleic anhydride obtained by oxidation of benzene (p. 247) and is optically inactive. Accordingly, a method has been devised whereby the amine can be resolved by the use of tartaric acid (G., 1920, 50, 276 Archiv der Pharmazie and Berichte der Deutschen Pharmazeutischen Gesellschaft, 1935, 408). 

Malic Acid occurs as a white or nearly white, crystalline powder or granules having a strongly acid taste. One gram dissolves in 0.8 mL of water and in 1.4 mL of alcohol. Its solutions are optically inactive. It melts at about 130°. 

Stereo Isomerism of Malic Acid.—On examination of the formula of malic acid it will be seen that one of the carbons is asymmetric i.e.j it has united to it four different elements or groups, viz., (—H), (—OH), (—COOH), and (—CH2—COOH). We should, therefore, expect to find that malic acid is optically active and that it exists in the three forms of dextroj levo, and inactive. This is in accordance with the facts. The formulas for the three stereo-isomeric forms of malic acid may be written as follows, corresponding exactly to those for lactic acid. 

Inactive Malic Acid.—When malic acid is prepared synthetically from inactive compounds, we obtain the inactive malic acid. Thus,... 

Isomerism of Tartaric Acid.—Examination of the formula for tartaric acid, which, by the facts given above, has its constitution fully established as symmetrical di-hydroxy succinic acid, shows the interesting fact that there are present two asymmetric carbon atomsy and that each of these has linked to it the same set of four different groups. We should, therefore, expect to find tartaric acid existing in the dextrOy the levo and the inactive forms. The stereo-chemical formulas similar to those of lactic and malic acids we may write as follows. 

This acid, the inactive by intra-molecular compensation and un-resolvable into optically active components, was first obtained by Pasteur by heating the cinchonine salt of dextro tartaric acid, to 170 . It may also be prepared by boiling the dextro tartaric acid with an excess of hydrochloric acid, or with sodium hydroxide. Also by long boiling with water alone or by heating with a small amount of water to 165°. When di-brom succinic acid is treated with silver hydroxide, or when malic acid is oxidized, in the presence of water, both meso-tartaric acid and racemic acid are formed. When meso-tartaric acid is heated to 200° it is partly converted into racemic acid. Meso-tartaric acid crystallizes in rectangular plates with one molecule of water. The water free acid melts at i40°-i45°. 

E)-caffeoyl- L-malic acid pneumoniae K. oxytoca Inactive ... 

E-caffeoyl-L-malic acid Enzymatic inhibition (anti-inflammatory) Inactive. [21]... 

The term racemic is used as a general term in describing stereo-isomers to indicate that an inactive substance consists either of a mixture of the dextro- and levo-rotatory forms or is produced as the result of the formation of a molecular compound from these forms (315). Thus the, acid which has been called inactive malic acid is said to be the racemic form of malic acid. 

This preconceived idea is incorrect and inactive malic acid is racemic and not internally compensated like mesotartaric acid. Active malic acid was obtained from the racemic form by crystallising with cinchonine by G. J. W. Bremer. ... 

Weiss JM, Downs CR (1923b) The salts of maleic, fumaric and inactive malic acids. J Am Chem... 

The optically inactive citric acid (8-67) is the most important representative of tricarboxylic hydroxy acids. Citric acid, as well as malic acid, occurs in many fruits (especially in lemons). Industrially, it is obtained from lemon juice or produced by fermentation of molasses using fungi Aspergillus niger. Along with malic acid, citric acid is used as an additive in widely different canning products... 

German name, Trauben-saure, is derived from the word for grapes. It is probable that it does not exist in grapes as racemic acid but that it is formed from the dextro acid as this transformation can easily be effected by the action of acids or even by water alone. When tartaric acid is prepared synthetically from succinic acid, from glyoxal, or from malic, maleic or fumaric acids either racemic acid or meso-tartaric acid is always formed. That is, synthetic reactions result in the formation of an inactive form. The methods of splitting racemic acid into its optically active components has been fully discussed. The sodium-ammonium racemate is the only salt that is of importance. This has been spoken of in connection with the method of splitting racemic acid into its components.. Like the free acid this salt exists, in dilute solution, as equal molecular parts of the dextro and levo forms. Only in concentrated solution does it exist as the racemate itself. 

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