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PubMed2003

The physical stability of thermally-stressed phospholipid-based emulsions containing methyl, propyl and heptyl parabens as model drugs.

The objectives of the studies presented herein was to investigate the mechanisms of emulsion instability under thermal stress (121 degrees C) by evaluating the effects of a lipophilic drug dissolved in the internal phase of an oil-in-water (o/w) emulsion on growth rate suppression and the apparent microviscosity. Model drugs used were methyl, propyl and heptyl paraben. The o/w emulsions were prepared using medium chain triglycerides as an internal phase in aqueous glycerol solutions emulsified with phospholipids. Concentrations of paraben in the internal phase varied from 0.2-0.8 M. Microfluidization was used to reduce the droplet size to the submicron range. Microviscosity was calculated from the measured anisotropy of a fluorophore probe (1,6-phenyl-1,3,5-hexatriene) using a modified Perrin's equation. Emulsion aliquots were subjected to thermal stressed at 121 degrees C the droplet growth rate was determined from periodic measurements of the mean droplet diameter using photon correlation spectroscopy. The growth rate decreased in the presence of parabens. Maximal growth suppression occurred at paraben concentrations of 0.4 M. However in deference to theoretical predictions of the effects of increasing co-solute concentrations based on Ostwalt ripening, the droplet growth rates increased at concentrations greater than 0.4M. The logarithm of the growth rate was linearly correlated to the interfacial rigidity (inverse microviscosity) of the emulsion which suggests that coalescence rather than molecular diffusion was primarily responsible for emulsion instability under the conditions studied.

Chemical Phenomena↗

PubMed2003

Determination of cisapride, its oxidation product, propyl and butyl parabens in pharmaceutical dosage form by reversed-phase liquid chromatography.

A simple, rapid and reproducible high-performance liquid chromatography (HPLC) assay for cisapride, its oxidation product (OP), propyl and butyl parabens in a pharmaceutical formulation is described. Chromatography was performed at room temperature by pumping acetonitrile-20 mM phosphate buffer pH 7 (50:50, v/v) at 1.5 ml min(-1) through C8 reversed-phase column. Cisapride, OP, propyl and butyl parabens were detected at 276 nm and were eluted at 9.7, 3.1, 5.1 and 7.1 min, respectively. Calibration plots were linear (r>0.999) for all compounds from 0.5 to 200 microg ml(-1) for cisapride and OP and 0.1-200 microg ml(-1) for propyl and butyl parabens. Detection limits for cisapride, OP, propyl and butyl parabens were 40, 46, 48 and 54 ng ml(-1), respectively. Forced degradation investigations showed that cisapride does not undergo degradation under heat, acidic and basic conditions but it was susceptible to oxidation. The proposed method was successfully applied to the assay of cisapride in the presence of preservatives and OP in a commercial suspension.

Chromatography, High Pressure Liquid↗

PubMed2001

Sorption of parabens by flexible tubings.

Flexible tubings are extensively used in pharmaceuticals, food industry, and in hospitals. This study was undertaken to compare various flexible tubings to determine their sorption characteristics, using methyl and propyl parabens. After 24 h, some tubings showed 100% sorption of propylparaben and over 40% for methylparaben. Significant losses were observed within a few hours using several tubings. For methylparaben, the losses were in the following decreasing order of sorption: Tygon, Clearflo, silicone, Nylotube, and Newtex. For propylparaben, the losses were in the following order: Tygon, Clearflo, silicone, Newtex, and Nylotube. Teflon, Zelite, and Vitube showed little to no losses of methyl and propylparaben over 120 h of study. The silicone tubing, refilled after 120 h with fresh methylparaben or propylparaben solutions, again showed significant losses within a few hours. The tubings show slow desorption when filled with the buffer vehicle. For Silastic tubing, increase in temperature from 25 to 40 degrees C, increase in pH from 3.5 to 6.5, tubing lot to lot variation, or curing with peroxide or platinum had little or no effect on paraben sorption. As expected, the sorption of parabens increased with increasing surface area of Silastic tubing. Results provided can be used to select the best tubings and to minimize paraben losses during production and filling of liquid pharmaceuticals andfood products containing these antimicrobial preservatives.

Adsorption↗

PubMed2004

Burkholderia cepacia infections associated with intrinsically contaminated ultrasound gel: the role of microbial degradation of parabens.

OBJECTIVE: To describe an outbreak of serious nosocomial Burkholderia cepacia infections occurring after transrectal prostate biopsy associated with ultrasound gel intrinsically contaminated with paraben-degrading microorganisms. METHODS: A retrospective chart review prompted by a blood culture isolate of B. cepacia. Identification of microorganisms in ultrasound gel in two Canadian centers and characterization by pulsed-field gel electrophoresis and assays for paraben degradation. SETTING: Two Canadian university-affiliated, tertiary-care centers in Newfoundland and Alberta. RESULTS: Six serious B. cepacia infections were identified at the two centers. Isolates of B. cepacia recovered from the blood of patients from both centers and the ultrasound gel used during the procedures were identical, confirming intrinsic contamination. Strains of Enterobacter cloacae isolated from ultrasound gel at the two centers were also identical. The ability to degrade parabens was proven for both B. cepacia and E. cloacae strains recovered from the ultrasound gel. CONCLUSIONS: Ultrasound gel is a potential source of infection. Contamination occurs at the time of manufacture, with organisms that degrade parabens, which are commonly used as stabilizing agents. There are far-reaching implications for the infection control community.

Aged↗

PubMed1975

Allergic paraben and benzyl alcohol hypersensitivity relationship of the "delayed" and "immediate" varieties.

From a review of the literature, and the results of scratch, intracutaneous and subcutaneous injections of patients with parbens and benzyl alcohol sensitivity of the delayed type characterized by allergic contact dermatitis and strongly positive patch patch tests, it would appear that such sensitivity is not usually accompanied by the immediate urticarial type of allergic sensitivity. This communication concerns itself with results of testing patients with clinical sensitivity and positive patch test reactions to the parabens or benzyl alcohol with scratch, intracutaneous and subcutaneous injections of these preservatives in order to determine the relationship of the "delayed" type of allergic hypersensitivity to the parabens and benzyl alcohol with the "immediate" variety of hypersensitivity. The parabens and benzyl alcohol are widely employed as preservatives for many allergenic extracts used in scratch and intracutaneous testing. In addition, these preservatives are used in injectable corticosteroid medicaments and in local anesthetic solutions. In order to determine whether the presence of these preservatives in allergenic extracts would produce false positive scratch or intracutaneous tests or might produce an immediate, urticarial or anaphylactic reaction in patients with allergic contact dermatitis and positive patch test reactions to these preservatives, two patients with positive patch test reactions and allergic contact dermatitis to the parabens and two with similar benzyl alcohol sensitivity were tested in the manner detailed in the following case reports.

Adrenal Cortex Hormones↗

PubMed2006

Cross-reactions among parabens, para-phenylenediamine, and benzocaine: a retrospective analysis of patch testing.

BACKGROUND: Parabens are alkyl ester derivatives of para-hydroxybenzoic acid and are the most commonly used preservatives in the cosmetic industry. Cross-reactions with para-amino compounds, namely, benzocaine and para-phenylenediamine (PPD), have been reported but are thought to be extremely rare. OBJECTIVE: To evaluate the rate of cross-reactivity between parabens, PPD, and benzocaine in a population of patients patch-tested in a hospital-based contact dermatitis clinic. METHODS: A retrospective analysis of 4,368 patients consecutively patch-tested between July 1989 and June 2005. RESULTS: Our study demonstrated that the rate of cross-reactions to parabens in PPD- and benzocaine-positive patients combined is 2%. CONCLUSION: This cross-reaction rate is significant in the tested population but still falls within the previously reported rates of sensitivity to parabens in the general population (0 to 3.5%).

Anesthetics, Local↗

PubMed2006

[Estrogenic activities of parabens].

OBJECTIVE: Studies indicated that parabens, used as anti-microbial agents in food, cosmetics, and pharmaceuticals, produced a positive uterotrophic response in vivo. They also damaged the late stages of spermatogenesis, altered proportion of pups born alive, and body weight of offspring. They reduced the number of sperm in the epididymis, and the sperm motile activity in male offspring. Parabens could compete with [3H] 17beta-estradiol for binding to the estrogen receptor. The proliferation of two estrogen-dependent cell lines MCF-7 and ZR-75-1 could be increased by parabens. They also increased expression of both transfected and endogenous estrogen-regulated genes in MCF-7 cells. The studies demonstrated parabens were weakly estrogenic.

Animals↗

PubMedDate not supplied

Liquid chromatographic determination of propyl paraben in cigarette filler.

A liquid chromatographic method for the quantitative determination of propyl paraben in cigarette tobacco filler has been developed. Propyl paraben is extracted from cigarette tobacco filler with acetonitrile and further purified using a silica Sep-Pak cartridge and ethyl acetate-petroleum ether (1 + 4) as eluting solvent. The purified extracts are analyzed by reverse-phase liquid chromatography using buffered water (pH 4)-acetonitrile (65 + 35) as mobile phase, with UV detection at 254 nm. Cut tobacco samples were fortified with 100 and 200 ppm propyl paraben. Average recoveries (N = 5) of propyl paraben were 98 and 94%, respectively, with coefficients of variation less than 4%.

Chromatography, Liquid↗

PubMed2002

Fast capillary electrochromatographic analysis of parabens and 4-hydroxybenzoic acid in drugs and cosmetics.

A fast capillary electrochromatographic method was developed for the analysis of paraben preservatives in drugs and cosmetics in the presence of their main metabolite and/or impurity, 4-hydroxybenzoic acid. The separation was optimized in a 75 num ID capillary, fully packed with 5 num C18 stationary phase, studying the effects of mobile phase pH and composition (buffer type and organic solvent content). The mobile phase 5 mM ammonium formate, pH 3.0, containing 65% acetonitrile allowed us to obtain the baseline separation of methyl-, ethyl-, propyl-, butyl-, and benzylparabens from a mixture in less than 2.5 min with repeatability and linearity using the short-end injection method (8 cm separation capillary effective length). Under the optimum experimental conditions, the method provided high separation efficiency for parabens, in the range of 129 312-140 325 number of theoretical plates per meter, and analyte quantitation limits (LOQs) in the range of 1.25-2.50 nug/mL. The method was successfully applied to the quantitative analysis of paraben preservatives in pharmaceutical and cosmetic industrial samples with direct injection or after reduced sample pretreatment.

Chromatography, High Pressure Liquid↗

PubMed1978

Thermodynamics of aqueous solutions of parabens.

The solubility of a related series of parabens was determined in water at four temperatures. The parabens chosen were the methyl through n-butyl p-hydroxybenzoates, and the temperature variations were 5 degrees increments from 25 to 40 degrees. These solutes are useful preservatives, especially combinations of the methyl and propyl ester derivatives. The chemical relationship of these compounds varied by successive linear methylene additions on the ester portion of the molecules. The thermodynamic values obtained for these aqueous systems could be related to these molecular variants since the remainder of the molecule was constant. For the overall thermodynamics, the free energy functions such as the ideal, actual, and excess were found to be smooth, nonlinear functions of the number of carbon atoms in the alkyl portion of the paraben esters. A linear relationship with the number of carbon atoms in the ester portion of these esters was found with the partial excess free energy of the solute.

Parabens↗

PubMed1981

Analysis of drug contamination from parabens in theophylline olamine.

Contaminants in a commercial enema sample of theophylline olamine were found to be derived from parabens and ethanolamine. These contaminants, whose presence was characterized by the loss of preservatives and solubilizing agent, were isolated directly from the drug sample and identified. A high-performance liquid chromatographic (HPLC) system was developed to separate completely and to measure quantitatively theophylline, the two impurities, 4-hydroxybenzoic acid and N-(2-hydroxyethyl)-4-hydroxybenzamide, and the remaining parabens. The material balance obtained from the results of quantitative HPLC indicated the formation of these impurities at the expense of parabens. TLC, IR, and UV spectrophotometry and NMR and mass spectrometric analyses were used for identification or for comparisons of the new compound and the known N-(2-hydroxyethyl)benzamide.

Benzoates↗

PubMed1983

Simultaneous determination of acetaminophen, guaifenesin, pseudoephedrine, pholcodine, and paraben preservatives in cough mixture by high-performance liquid chromatography.

The separation and simultaneous determination, by high-performance liquid chromatography, of acetaminophen (I), guaifenesin (II), pseudoephedrine hydrochloride (III), and pholcodine (IV), together with a series of parabens (methyl to butyl, V-VIII) in a cough mixture, has been demonstrated using a chemically bonded octadecylsilane stationary phase with a mobile phase of methanol-water-acetic acid (45:55:2) containing the ion-pairing agent octanesulfonic acid. Retention volumes for the active ingredients were 3.8 ml, 5.4 ml, 9.4 ml, and 15.6 ml for compounds I-IV, respectively. Corrected retention volumes for the parabens [5.4 ml for methyl (V), 9.6 ml for ethyl (VI), 18.5 ml for propyl (VII), and 37.9 ml for butyl (VIII)] showed an exponential relationship with chain length of the esterifying alcohols. Excipients did not interfere with the estimation of any of the compounds, hence pretreatment of the sample was unnecessary. Average recoveries of the active ingredients and of the parabens from laboratory prepared samples were essentially 100% of theoretical with standard deviations of 1.7, 0.3, 1.5, 0.3, 0.3, 3.3, 0.7, and 2.7% for I-VIII, respectively.

Acetaminophen↗

PubMed1995

Transesterification reactions of parabens (alkyl 4-hydroxybenzoates) with polyols in aqueous solution.

Accelerated stability tests of aqueous solutions containing parabens and polyols were performed using concentrations similar to pharmaceutical and cosmetic formulations. Reaction products were detected in these solutions by HPLC and identified by chromatographic and spectroscopic means. Using xylitol and methylparaben as model reactants, three unknown peaks having the relation 1:2:4 were obtained together with the hydrolysis product 4-hydroxybenzoic acid. Diode array detection gave identical UV spectra for each peak with a maximum at 255 nm. The structures of the isomeric 1-, 2-, and 3-xylityl 4-hydroxybenzoic acid esters were proved by means of LC-MS, GC-MS, and NMR and correlated to the peaks in the HPLC chromatograms. The rate of the transesterification was shown to be highest in strongly alkaline medium (ph 10-11), whereas equilibration of the reaction was optimally balanced at pH 8-9. An increase of polyol concentration enhanced the formation of the esters. The reactivity of different substituted parabens was higher in the case of parabens with a short alkyl ester function. Similar reaction profiles were observed with C3-C6 polyols, but no transesterification took place when aldoses were used.

Chromatography, High Pressure Liquid↗

PubMed1989

Relationships between the resistance of yeasts to acetic, propanoic and benzoic acids and to methyl paraben and pH.

Minimum inhibitory concentrations of acetic, propanoic and benzoic acids and methyl paraben were determined at pH 3.50 for 22 isolates of 11 yeast species, differing in their resistance to preservatives. Growth in the presence of benzoic acid enhanced the resistance of yeasts to benzoic and the other weak acid preservatives, but not to methyl paraben. Resistance to acetic, propanoic and benzoic acids was strongly correlated, but was not closely related to resistance to methyl paraben. Minimum pH for growth was not related to resistance to the weak acids. The results suggest that growth in the presence of weak-acid preservatives involves a common resistance mechanism.

Acetates↗

PubMed2005

Thermodynamics of solubility, sublimation and solvation processes of parabens.

Saturated vapor pressures for a number of parabens (methyl- (MePB); ethyl- (EtPB), n-propyl- (PrPB) and n-butyl- (BuPB)) were obtained and from their respective temperature dependences the sublimation enthalpy, DeltaH(sub)( degrees ), and sublimation entropy, DeltaS(sub)(degrees), as well as their respective relative fractions in the process calculated. The sublimation enthalpies are: DeltaH(sub)(degrees)(MePB)=98.8+/-0.8; DeltaH(sub)(degrees)(EtPB)=100.9+/-0.7; DeltaH(sub)(degrees)(PrPB)=123.7+/-0.6; DeltaH(sub)(degrees)(BuPB)=108.4+/-0.8 kJmol(-1). The obtained values are discussed with regard to X-ray data from the literature. Theoretical calculations of the respective crystal lattice energies were carried out and compared to the experimental data. The following parameters were analyzed: (a) energetic contribution of van der Waals forces and hydrogen bonding to the total packing energy of the crystals; (b) contributions of the different fragments of the paraben molecules to the packing energy; (c) influence of bias of the supposed C-H distances on the result of the calculation procedure. Enthalpies of evaporation were estimated from the measured enthalpies of sublimation and enthalpies of fusion, and compared with literature data. Moreover, the thermodynamic functions of solvation of the molecules in water and in a number of n-alcohols were evaluated. The thermodynamic terms (Gibbs energy, enthalpy and entropy) of the solvation process were split up in their respective specific and nonspecific fraction, and these values compared for all combinations of parabens and solvents. The influence of mutual saturation of the phases in the water-octanol system on the partitioning process of the molecules is also discussed.

Entropy↗

PubMed2001

Antibacterial effect of parabens against planktonic and biofilm Streptococcus sobrinus.

Tooth decay is an infectious disease caused by bacteria immobilized on the tooth surfaces. Eradication of these bacteria, for example Streptococcus sobrinus (S. sobrinus), from the oral cavity is essential in the prevention and treatment of tooth decay. We have tested the antimicrobial effect of several paraben derivatives such as methyl (MP), ethyl (EP), propyl (PP) and butyl (BP) against immobilized and planktonic S. sobrinus. The antibacterial effect was as follows: MP>EP>PP=BP on immobilized bacteria and MP>EP=PP>BP on planktonic bacteria. An antibacterial synergistic effect was found between several combinations of parabens on immobilized and planktonic S. sobrinus. Our results indicate that parabens are potential antibacterial agents against immobilized or planktonic bacteria found in the oral cavity.

Anti-Bacterial Agents↗

PubMed2005

Determination of parabens in pharmaceutical formulations by solid-phase microextraction-ion mobility spectrometry.

Solid-phase microextraction (SPME) coupled with ion mobility spectrometry (IMS) was used for the detection and quantitation of 4-hydroxybenzoate preservatives, methylparaben, ethylparaben, propylparaben, and butylparaben, in commercial pharmaceutical products. For the first time, SPME-IMS is described for the simultaneous detection, separation, and quantitation of multiple analytes in complex matrixes. The parabens are extracted from the samples using SPME, and the analytes on the fiber are heated by the IMS desorber unit and vaporized into the drift tube. The four preservatives differing only by a methyl group were separated in less than 18 ms. The analytical procedure was optimized for fiber coating selection, extraction time, sample pH, sample volume, ionic strength, and IMS conditions. Separation characteristics such as resolution, theoretical plates, and drift times of the parabens were also evaluated based on the direct interfacing of SPME to IMS. The conditions were tested using six over-the-counter topical products containing various combinations of preservatives. Analysis of the samples by SPME-IMS using benzyl paraben as an internal standard yields good comparison to an HPLC method, thereby reinforcing the applicability of this technique as a method for routine analysis. Limits of detection were 10 ng/mL for methylparaben and ethylparaben and 5 ng/mL for propylparaben and butylparaben. Good linearity range and reproducibility of less than 8% were obtained.

Calibration↗

PubMed1999

Physical properties of parabens and their mixtures: solubility in water, thermal behavior, and crystal structures.

The peculiar solubility behavior of propylparaben (propyl ester of 4-hydroxybenzoic acid) in aqueous solution, when tested separately and together with methyl-, ethyl-, and butyl-parabens, has been investigated in detail. The results clearly indicate that the decrease in solubility (approximately 50% compared to the solubility value of propylparaben alone) is typical of those mixtures containing also ethylparaben, as demonstrated by solubility experiments on binary, ternary, and quaternary mixtures of the parabens. Phase diagrams of all the six binaries show that propylparaben and ethylparaben are the only pair that form almost ideal solid solutions near the melting temperatures. Moreover, phase-solubility analysis shows that propylparaben and ethylparaben, at room temperature, can also form solid solutions whose solubility is related to the composition of the solid phase at equilibrium. To achieve an independent confirmation of the possible solid solution formation that supports the above interpretation of the solubility behavior, the crystal structures of the four parabens have been examined and isostructurality has been found to exist only between ethylparaben and propylparaben. Powder X-ray diffraction has also been performed on ethylparaben, propylparaben, and their solid solutions obtained by recrystallization from water. The progressive shift of distinctive diffraction peaks with phase composition clearly indicates that propylparaben and ethylparaben form substitutional solid solutions. The small value (<1) of the disruption index provides thermodynamic support for substitutional solid solutions based on isostructural crystals.

Calorimetry, Differential Scanning↗