Propyl 4-hydroxybenzoate, 4-hydroxybenzoic acid

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]. 

Liquid dosage forms which are disperse systems (colloidal, i.e., microspheres, nanoparticles, and micelles suspensions and emulsions) often contain preservatives which are methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid in various combinations. A typical example is the antacid suspensions which have high pH values which make the esters of the preservatives susceptible to hydrolysis. One way to circumvent this problem is to use several preservatives in combination with the hope that some quantities of the preservatives will remain to prevent the suspension from microbial attack. A report showing the assay of the four esters and the parent acid (one of the decomposition products) in drug products in which all the preservatives were used has been given [13]. 

Scheiffer, G. W., Palermo, P. J., and Pollard-Walker, S. (1984), Simultaneous determination of methyl, ethyl, propyl, and butyl 4-hydroxybenzoates and 4-hydroxybenzoic acid in liquid antacid formulations by gas chromatography, J. Pharm. Sci., 73,128. 

These compounds include the methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid. In the United Slates and a number of other countries, the methyl and propyl esters are preferred, while European food processors favor the ethyl and butyl esters. The parabens were first described in 1924 as having antimicrobial activity and initially were used in cosmetic and pharmaceutical products. 

This part of the chapter describes HPLC techniques for the separation and determination of preservatives, as follows S02, postharvest preservatives (PPs), benzoic acid (BA), sorbic acid (SA), and the ethyl, methyl, propyl esters of 4-hydroxybenzoic acid (EsHBA) and 5-nitrofury-lacrylic acid (5-NFA). The propionic, lactic, acetic acids are discussed in the chapter on organic acids. 

Flak and Schaber (5,62) used reverse-phase HPLC for the quantitative and simultaneous determination of benzoic acid and sorbic acid, as well as 4-hydroxybenzoic acid, salicylic, 5-nitrofurylacrylic, and p-chlorobenzoic acid and the EsHBA (methyl, ethyl, propyl) in wines and beverages. The first five compounds can be determined by isocratic elution from a Clg column using 0.12 M acetate, pH 3.8 acetonitrile (85 15), and all may be separated with gradient elution (increasing acetonitrile from 10 to 60%, with a simultaneous decrease of the pH of the acetate buffer from 3.9 initially to 3.3). 

A paired-ion, reversed-phase high-performance liquid chromatographic method was developed for the simultaneous determination of sweeteners (dulcin, saccharin-Na, and acesulfame-K), preservatives (sodium dehydroacetate, SA, salicyclic acid, BA, succinic acid, methyl-para-hydroxybenzoic acid, ethyl-para-hydroxybenzoic acid, n-propyl-para-hydroxybenzoic acid, n-butyl-para-hydroxybenzoic acid, and isobutyl-para-hydroxybenzoic acid), and antioxidants (3-tertiary-butyl-4-hydroxyanisole and tertiary-butyl-hydroquinone). A mobile phase of acetonitrile-50 ml aqueous tr-hydroxyisobutyric acid solution (pH 4.5) (2.2 3.4 or 2.4 3.6, v/v) containing 2.5 mM hexadecyltrimethylammonium bromide and a Clg column with a flow rate of 1.0 ml/min and detection at 233 nm were used. This method was found to be very reproducible detection limits ranged from 0.15 to 3.00 p,g. The retention factor (k) of each additive could be affected by the concentrations of hexadecyltrimethylammonium bromide and a-hydroxyisobu-tyric acid and the pH and ratio of mobile phase. The presence of additives in dried roast beef and sugared fruit was determined. The method is suitable for routine analysis of additives in food samples (81). 

Figure 6.1 UV chromatograms of the test mixture of four / -hydroxybenzoic acid esters (1, methyl 2, ethyl 3, propyl 4, butyl) after the column and after the NMR flow cell at flow rates of (a) 1.0 and (b) 0.1 ml/min conditions column, LiChrospher RP select B, 125 x 4 mm id, 5 Jim, spectrometer, Bruker DRX 600 probe head, 4 mm z-gradient LC probe, active volume 120 a1 eluents, acetonitrile (A) and D2O (B) gradient, t = Omin A/B (40/60), t = 8 min A/B (70/30) at a flow rate of 1.0 ml/min and t = 80 min A/B (70/30) at a flow rate of 0.1 ml/min...

SYNS ASEPTOFORM P BETACIDE P BONOMOLD OP 4-HYDROXYBENZOIC ACID PROPYL ESTER p-HYDROXYBENZOIC ACID PROPYL ESTER NIPASOL p-OXYBENZOESAEUREPRO-PYLESTER (GERMAN) PARABEN PARj SEPT PASEPTOL PRESERVAL P PROPYL p-HYDROXY-BENZOATE n-PROP X p-HYDROXYBENZOATE PROPYLPARABEN (FCC) PROPYLPARASEPT PROTABEN P TEGOSEPT P... 

Esters of 3,4 -tri-hydroxybenzoic acid R = C3H7 (Propyl) ss CgHp (Octyl)... 

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. 

Parabens (methyl, ethyl, propyl, and butyl esters of para-hydroxybenzoic acid) are used as preservatives in concentrations of 0.1-0.3% in pharmaceutical formulations and in concentrations of 0.01-0.1% in cosmetics and foods. In such concentrations they are devoid of systemic toxic effects, but allergic reactions have been reported. 

Parabens [Napp]. TM for the methyl, propyl, butyl, and ethyl esters of p-hydroxybenzoic acid. Antimicrobial agents for foods and pharmaceuticals. Approved by FDA as GRAS. 

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). 

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. 

Synonym 4-Hydroxybenzoic acid propyl ester Source Cheng, K.-W. Tang, M. Chen, Y.-P. Fluid Phase Equil. (2002), 201(1), 79-96. 

Benzoic xid, 4-hydroxy-, propyl ester, sodium salt Caswell No. 714A EINECS 252488-1 EPA Pesticide Chemical Code 061204 4-Hydroxybenzoic acid, propyl ester, sodium salt Nipasol M Sodium Parasept Propyl p-hydroxybenzoate, sodium salt Propylparaben sodium Propylparaben, sodium salt Sodium 4-propoxy-carbonylphenoxide Sodium propylparaben. Preservative, bactericide, fungicide for pharmaceuticals, cosmetics, foods, medicinal preparations, industrial applications. Laboratories Ltd Nipa. 

Synonyms cas 94-13-3 aseptoformp betacidep bonomoldop 4-hydroxybenzoic acid propyl ester p-... 

HYDROXYBENZOIC ACID PROPYL ESTER NIPASOL p-OXYBENZOESAUREPROPYLESTER PARABEN PARASEPT PASEPTOL... 

E216 /7-Hydroxybenzoic propyl From benzoic acid Preservative Similar to E 214 Similar to E 214... 

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