Malic acid/malate

Malic acid Malate oxidase, NAD(P)+-malate dehydrogenase Wines Flavour blender, prevents turbidity, fermentation process control, affects acidity... 

Apfelsaure (Malat) malic acid (malate) Apiezonfett apiezon grease Appretur(mittel) finish Aquilibrierung equilibration Aquivalentdosis (Sv) dose equivalent Aquivalenzpunkt (Titration) end point, point of neutrality Aramide... 

Colourless prisms m.p. 130 C. Manufactured by treating maleic anhydride with water. It is converted to the anhydride by heating at By prolonged heating at 150 "C or by heating with water under pressure at 200 C, it is converted to the isomeric (trans) fumaric acid. Reduced by hydrogen to succinic acid. Oxidized by alkaline solutions of potassium permanganate to mesotartaric acid. When heated with solutions of sodium hydroxide at 100 C, sodium( )-malate is formed. Used in the preparation of ( )-malic acid and in some polymer formulations. 

Alkyl hahdes in the presence of silver oxide react with alkyl malates to yield alkoxy derivatives of succinic acid, eg, 2-ethoxysuccinic acid, H00CCH2CH(0C2H )C00H (12,13). A synthetic approach to produce ethers of malic acid is the reaction of malic esters and sodium alkoxides which affords 2-alkoxysuccinic esters (14). 

Ca.ndy. Its low melting point and sugar inversion properties make malic acid a desirable acidulant, especially in hard candy products (44,45). Due to their insolubiUty, hard water salts can cause clouding of the finished product. However, because of the higher solubiUty of calcium malate [17482-42-7] relative to alternative acidulants, clarity of the finished product is enhanced. Additionally, in sugar confectionery products where acidulation may exceed 2.0%, malic acid can provide economic benefits. 

The mother liquors from the original cr3 Stallization and recrystallizations are treated in a similar manner and the sodium malate solutions are united and reserved for the recovery of i-malic acid (Note 7). The recovered amine amounts to 75-80 g. and contains 40-50 per cent excess /-amine. 

In the resolution of 1-phenylethylamine using (-)-malic acid, the compound obtained by recrystallization of the mixture of diastereomeric salts is (/ )-1-phenylethylammonium (S)-malate. The other component of the mixture is more soluble and remains in solution. What is the configuration of the more soluble salt ... 

The strongest known producer of j8-poly(L-malic acid) has been identified as Aureobasidium sp. providing 61 g of polymer from 1 liter of culture medium [5,6]. 8-Poly(L-malate, Ca -salt) of the culture broth was first separated from accompanying bulk pullulan by methanol precipitation. The water-redisolved precipitate was converted to the polymer acid by passage over Amberlite IR-120B (H -form). Thus, the best to-day producers of... 

The purification of j8-poly(L-malic acid) from A o-basiae has been reported involving methanol precipitation of the polymer in the form of the Ca salt [5]. This is possible because a high concentration of CaCOs is present in the growth medium. Unfortunately, the polymer acid is not soluble in aceton thus missing an additional purification step. In our hands, purification of jS-poly(L-malate) from several Aureobasidiae strains was unsatisfactory because of low yields and resisting impurities. 

Infrared spectra and the degree of specific rotation show typical features of the malic acid polyester (Table 3). Ultraviolet absorbance spectra of )3-poly(L-malate) from both P. polycephalum and Aureobasidium sp, A-91 are similar and are reminiscent of malate itself [4,5]. For a solution of 1.0 mg/ml polymer, absorbance increases from 0.40 units at 230 nm to 10 units at 190 nm wavelength. After saponification and pH-neutralization, the absorbance increased from 8.7 units at 230 nm to 100 units at 190 nm. 

Substantial amounts of polymalatase have been isolated from plasmodial extracts. This may refer to stored enzyme before secretion, because /3-poly(L-malate) is not degraded in plasmodia [24]. Several other fungi were found to secrete /3-poly(L-malate) degrading activities to L-malic acid (Ratberger, Molitoris and Holler, unpublished results). These enzymes have not yet been purified and characterized. 

Figure 26 Polymer (1) poly(ethyladamantyl P-malate) is hydrophobic and polymer (2) poly(P-malic acid-co-ethyladamantyl P-malate is hydrophilic. Both of these polymers are used as carriers for different drugs [148].

Poly-j3-malate is readily degraded completely to L-malic acid under both acid and base conditions [108], and it can also be hydrolyzed by enzymes within the cell [105,106]. Recently, several bacteria were isolated which were able to utilize poly-/i-malate as sole carbon source for growth [109]. Because the polymer is biodegradable and bioadsorbable, it is of considerable interest for pharmaceutical applications, especially in controlled-release drug delivery systems [97,98]. Chemical routes to poly-/ -malate are expected to provide materials with various properties [110]. 

Poly(L-malate) [poly(malic acid) (PMA)], is a water-soluble polyanion produced by slime molds and some yeasts such as Physarum polycephalum or Aureobasidium pullulans, respectively. Its function and metabolism has been studied during the last few years [122-125]. Recently, several PMA-degrad-ing bacteria have been isolated, and a cytoplasmic membrane-bound PMA hydrolase was purified from Comamonas acidovans strain 7789 [126] that... 

The change with the concentration cannot be due to the reversible formation and decomposition of a lactone of the ordinary type because we get the effect with ethyl malate as well as with malic add. The change cannot be due to a reversible conversion of laevo-malic acid into dextro-malic add, because then a solution of equivalent amounts of dextro- and laevo-malic acids would become optically active on addition of salts, adds and bases. Hydrochloric add or sodium hydroxide imparts no activity to a solution of d/-malic add. The changes on adding electrolytes to a solution of dextro-malic add are equal and opposite in sign to the changes in laevo-malic acid under the same conditions. 

Equations Malic acid first reacts with CaC03 to yield the soluble calcium malate that goes into the filtrate, whereas the insoluble calcium carbonate is filtered off and rejected. Thus,... 

The reaction mixture for a coupled assay includes the substrates for the initial or test enzyme and also the additional enzymes and reagents necessary to convert the product of the first reaction into a detectable product of the final reaction. The enzyme aspartate aminotransferase (EC 2.6.1.1), for instance, results in the formation of oxaloacetate, which can be converted to malic acid by the enzyme malate dehydrogenase (EC 1.1.1.37) with the simultaneous conversion of NADH to NAD+, a reaction which can be followed spectropho-tometrically at 340 nm ... 

The enzyme malate synthase also synthesises (S )-malic acid from glyoxylic acid (OHC-CO2H) and the thioester acetyl-coenzyme A (CH3CO.SC0A this may be regarded as a source of the nucleophile CH2CO.SC0A). 

Since the formation of optically active, dioxolanone-based di-enolates was not successful, a consecutive alkylation strategy was developed for a short synthesis of (-)-wikstromol (ent-3) from (-)-malic acid (99) (Scheme 25). The first alkylation reaction was analogous to that reported for the enantioselective total synthesis of (-)-meridinol (97). In order to avoid a reduction/re-oxidation sequence and an almost unselective second alkylation, two disadvantages of the synthesis of meridinol (97) [55], we planned to use a different strategy for the second alkylation. Therefore, we have focused our strategy on two stereoselective alkylation reactions, one of dialkyl malates and one of a dioxolanone prepared thereof. Both alkylation reactions were previously described by Seebach and coworker [56, 63, 64]. The... 

The best compromise with respect to reactivity and availability of the starting material was the use of diisopropyl malate 107. This malic acid ester is easy to prepare and its alkylation with various benzyl bromides can be achieved with good yields (53-67%, not optimized) and high stereoselectivities (dr 95 5 for 120 and 121). An exception with respect to the stereoselectivity was the 2,4,6-trimethylbenzyl substituted succinate 122, which was obtained in a dr of only 83 17 (Fig. 6) [71]. 

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