Soluble propyl hydroxybenzoate

Synonyms E217 propyl 4-hydroxybenzoate sodium salt sodium propyl hydroxybenzoate soluble propyl hydroxybenzoate. 

Synonyms. Sodium Propylparaben Soluble Propyl Hydroxybenzoate. Proprietary Name. Nipasol M Sodium C,oHnNa03 = 202.2 CAS—35285-69-9... 

The use of preservative eombinations may be used to extend the range and speetrum of preservation. Thus, in the series of alkyl esters of 4-hydroxybenzoic (/ -hydroxybenzoic) acid (parabens), water solubility deereases in the order methyl, ethyl, propyl and butyl ester. By eombining these produets it is possible to aehieve a situation where both the aqueous and oil phase of an emulsion are proteeted. 

These esters of p-hydroxybenzoic acid have been used primarily to prevent growth of molds but in higher concentrations possess some weak antibacterial activity. Their effective use is limited by low aqueous solubility and by reports of stinging and burning sensations related to their use in the eye. They bind to a number of nonionic surfactants and polymers, thereby reducing their bioactivity. They are used in combination, with the methyl ester at 0.03-0.1% and the propyl ester at 0.01-0.02%. Parabens have also been shown to promote corneal absorption [140]. 

Fig. 4 Van t Hoff plots (left) and Hildebrand plots (right) representing the influence of temperature (absolute) on the aqueous mole fraction solubility of adipic acid (AD), acetaminophen (AM), methylp-hydroxybenzoate (MP), ethylp-hydroxybenzoate (EP), propyl p-hydroxybenzoate (PP), and butyl p-hydroxybenzoate (BP). The data represented by O were taken from Ref. 24, while the data represented by x were obtained from Ref. 23. (Reproduced with permission of the copyright owner, Elsevier Science Publishing Co.)...

Acidic preservatives are the most widely used for oral preparations, such as the p-Hydroxybenzoic acid esters and salts of benzoic acid. These are adequately soluble in aqueous systems and possess both antifungal and antibacterial properties. Methyl and propyl p-hydroxybenzoic acid are often used together in a 10 1 ratio. Concomitant use of multiple esters makes possible a higher total preservative concentration owing to the independent solubilities of each and, according to some researchers, maximizes the antimicrobial effect. 

The alkyl esters (methyl, ethyl, and propyl) of p-hydroxybenzoic acid (the parabens) are widely used for their antifungal properties. The preservative effect of parabens tends to increase with increasing molecular mass. The methyl ester appears to be more effective against molds, whereas the propyl ester is more effective against yeasts (favored for oils and fats, for solubility reasons) (Gonzalez, Gallego, and Valcarcel, 1998). 

Beilstein Handbook Reference) AI3-24370 Benzoic acid, 2-hydroxy-, 2-methylpropyl ester BRN 2615955 EINECS 201-729-9 FEMA Mo, 2213 2-lsobutoxycarbonyiphenol Isobutyl o-hydroxybenzoate Isobutyl salicylate 2-Methyl-1-propyl salicylate 2-Methylpropyl o-hydroxybenzoate NSC 62140 Salicylic acid, isobutyl ester. Used in perfumery. Liquid mp n 6.9 bp = 261 d = 1.0639 7.m = 238 rtm (cyclohexane) insoluble in HzO, soluble in EtOH, EtzO, CCl4. 

As p-hydroxybenzoic acid esters present a relatively high pKa value (approx. 8.5), their antimicrobial action is less dependent on the pH value of the type of food to be preserved. In this respect they are superior to the organic preservative acids. Unfavourably, as in the case of phenol, p-hydroxybenzoic acid esters may be linked to some extent to proteins, emulsifiers or other food components on account of their phenolic hydroxylic-group and thus be inactivated. The antimicrobial action of the p-hydroxybenzoic acid esters is proportional to the alkyl chain length. Thus the antimicrobial action of the methyl ester is some 3 to 4 times, that of the ethyl ester some 5 to 8 times, that of the propyl ester about 25 times as powerful as phenol (Thompson, 1994). However, superimposed on this effect may be the water solubility of the esters, which is inversely proportional to the alkyl chain length. Since the activity spectra of the individual p-hydroxybenzoic acid esters are different, the application of mixtures can be profitable. 

Ethyl 4-hydroxybenzoate is a highly effective preservative with moderately good solubility in water. The spectrum of effectiveness in demonstrated by the MIC in Table 81. As a food preservative ethyl 4-hydroxybenzoate is often used in combination with propyl 4-hydroxybenzoate (8.1.11.3.) thus it is possible in most cases to use smaller overall amounts of alkyl 4-hydroxybenzoate than would otherwise be necessary. The favourable properties of ethyl 4-hydroxy benzoate makes it also highly suitable for preserving cosmetics and pharmaceuticals most frequently mixtures of alkyl 4-hydroxybenzoates are used. 

In addition, 4-hydroxybenzoic add is widely used together with its alkyl esters (generally known as parabens) and salts. The most common are methyl-, ethyl-, propyl- and butyl- esters and are generally known as methylparaben, ethylparaben, etc. The antimicrobial activity of these chanicals increases as the carbon number of the alkyl chain increases, while, by contrast, their water solubility decreases in parallel. The antimicrobial activity of the individual esters is generally selective, so their mixtures offer powerful antimicrobial activity against an extremely broad spectrum of microorganisms This is the reason why a lot of cosmetics and skin care products are preserved with parabens both in Europe and the United States. 

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