Preservatives hydroxy benzoic acid esters

As the effectiveness against bacteria is weak, weaker than the activity against moulds, 2-phenyl ethanol is in general applied in combination with other microbicides, e.g. with p-hydroxy-benzoic acid esters (Section 6.1.10), quaternary ammonium compounds (Section 16-1), p-chloro-m-cresol (Section 5.3.1) for the preservation of cosmetic and pharmaceutical products. It is especially effective in acidic media. 

Phenoxy ethanol is mentioned in the EC positive list of preservatives for cosmetic products (maximum authorized concentration 1%) In general it is applied in combination with other preservatives, such as />-hydroxy benzoic acid esters (Section 6.1.10), l,2-dibromo-2,4-dicyanobutane (Section 15.11) and others. More effective is the 2-phenoxy ethanol hemiformal (Section 3.1.3). 

Phenol acids are phenols in which there is also a carboxylic acid group attached to the benzene ring. They include salicylic acid (ortho-hydroxybenzoic acid) and para-hydroxy-benzoic acid (Figure 25.8). Acetylsalicylic acid (aspirin) and sodium salicylate are derivatives of salicylic acid. Like phenol, they have antipyretic and analgesic properties. The methyl, ethyl and propyl esters of para-hydroxybenzoic acid (parabens) are used as preservatives in pharmaceuticals, cosmetics and foodstuffs. 

The second group consists of preservatives (see Sect 23.8), used to guarantee the microbiological quality of the product throughout its shelf life. For example esters of hydroxy-benzoic acid, quaternary ammonium substances and sorbic acid are widely used in pharmaceutical and cosmetic preparations. Other preservatives that are used include phenol, chlorhexidine, benzoic acid and benzyl alcohol. 

In comparison with the lower p-hydroxybenzoic acid alkyl esters the butyl ester is far and away the most effective one and presents an equalized spectrum of effectiveness (see Table 81). However, the application of the butyl ester as a preservative in cosmetics, toiletries and pharmaceuticals is, in spite of its high activity, limited because of its low water solubility and high log POW. But combinations of p-hydroxy-benzoic acid butyl ester with the lower alkyl esters perform excellently. 

AI3-02955 Benzoic acid, 4-hydroxy-, phenylmethyl ester Benzoic acid, p-hydroxy-, benzyl ester Benzyl 4-hydroxybenzoate Benzyl p-hydroxybenzoate Benzyl parahydroxybenzoate Benzyl Parasept Benzyl Tegosept Benzylparaben EINECS 202-311-9 Nipabenzyl NSC 8080 Parosept Phenylmethyl 4-hydroxybenzoate Solbrol Z. Among the most widely used preservatives in food, drugs, and cosmetics. Preservative, bactericide, fungicide for pharmaceuticals, cosmetics, foods, medicinal preparations, industrial applications. Crystals mp = 110-112°. Nipa. 

CAS 94-18-8 EINECS/ELINCS 202-311-9 Synonyms Benzoic acid, 4-hydroxy-, phenyl methyl ester Benzyl 4-hydroxybenzoate Benzyl p-hydroxybenzoate Phenylmethyl 4-hydroxybenzoate Definition Ester of benzyl alcohol and p-hydroxybenzoic acid Empirical C14H12O3 Toxicology TSCA listed Uses Preservative, bactericide, fungicide for foods, pharmaceuticals, industrial applies. antimicrobial in cosmetics Regulatory BP compliance Manuf./Distrib. Aldrich http //www.sigma-aldrich.com-, Alfa Aesar http //www.aifa.com-, Archimica Inc http //www.archimica.com-. 

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