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PubMed2005

Propyl paraben induces potassium efflux in Escherichia coli.

OBJECTIVES: Parabens are currently used as antibacterial preservatives in pharmaceutical, cosmetic and food products but there are no precise data concerning their activity on bacterial membranes. METHODS: We analysed the cytoplasmic potassium release during propyl paraben addition by using a selective electrode. Various conditions were assayed to investigate the bacterial paraben susceptibility. We compared the activity of propyl paraben with the activities of colicin A and polymyxin B. RESULTS: Propyl paraben induced potassium efflux that was related to the porin expression in the bacterial outer membrane. In addition, the presence of spermine, previously described as an efficient OmpF channel-blocker, protected susceptible cells against paraben activity. CONCLUSIONS: Propyl paraben induced potassium release in susceptible Escherichia coli cells similar to that observed with polymyxin B. Moreover, this efflux depended on porin channel activity. This permeabilizing effect is probably related to antibacterial properties of paraben molecules.

Anti-Bacterial Agents↗

PubMed2006

Enterobacter gergoviae and the prevalence of efflux in parabens resistance.

OBJECTIVES: In order to characterize the mechanism involved in parabens resistance, we studied 13 Enterobacter gergoviae collected from diverse cosmetic formulations containing parabens as preservatives and 10 isolates from clinical or industrial sources. METHODS: RAPD and ERIC-PCR were employed and compared for the epidemiological typing. To study antibiotic and paraben susceptibility, the standard disc diffusion method and the 2-fold dilution method in Luria-Bertani medium were used. Characterization of porins was performed using immunodetection with polyclonal antibodies. Resistance mechanisms against parabens membrane permeabilization were evaluated by measuring K(+) efflux using a specific electrode. mar regulon identification and comparison were carried out. RESULTS: Epidemiological typing confirmed that most of the cosmetic formulations were contaminated by unrelated strains. All of the E. gergoviae strains presented high methylparaben MICs, ranging from 1 to 3.8 g/L, values that were 2-5 times higher than for Escherichia coli or Enterobacter aerogenes, even in strains overexpressing MarA. These MICs decreased in the presence of phenylalanine arginine beta-naphthylamide, pinpointing efflux as a major mechanism of parabens resistance even in E. gergoviae clinical strains. CONCLUSIONS: This is the first report showing the role of active efflux in the parabens resistance in E. gergoviae, a mechanism that may explain its frequent isolation in parabens-containing cosmetics compared with other enterobacterial species. Paraben efflux seems to be regulated by a mar-independent process in E. gergoviae.

Anti-Bacterial Agents↗

PubMed2003

[Studies for analyzing phenoxyethanol and parabens in commercial lotions].

Both phenoxyethanol and parabens are kinds of preservatives in cosmetics and are nominated as the restricted ingredients in cosmetics in Japanese Pharmaceutical Affairs Low. So the analytical methods for phenoxyethanol and parabens were investigated by HPLC. After adding methanol to phenoxyethanol and parabens in lotions, the testing solutions were analyzed by HPLC using the ODS column (CAPCELL PAK C18 column, 4.6 x 250 mm), the mixture either of 50 mmol/l phosphate(pH3.5) and acetonitrile (7:3) for phenoxyethanol or of 50 mmol/l phosphate buffer(pH3.5) and acetonitrile (3:2) for parabens and the detection wavelength of either 270 nm for pehnoxyethanol or 255 nm for parabens. The working curves from 0.5 to 5 micrograms/ml passed through the origin. There were no interference of peaks of phenoxyethanol and parabens from the cosmetics. Eleven lotions out of 42 lotions did not have phenoxyethanol. Phenoxyethanol in thirty-one cosmetics ranged from 0.009 to 1.043% and those average was 0.264%. Parabens, especially methylparaben, were detected in all lotions. The amounts of parabens ranged from 0.016 to 0.267% and their average was 0.120%. There were 7 kinds of lotions whose contents of phenoxyethanol and methylparaben were below 0.1%.

Acetonitriles↗

PubMed2002

Effects of butyl paraben on the male reproductive system in mice.

Parabens are alkyl ester compounds of p-hydroxybenzoic acid widely used as preservatives in foodstuffs, cosmetics, toiletries and pharmaceuticals. These compounds are known to exert a weak estrogenic activity in estrogen receptor assays in vitro and in uterotrophic assays in vivo. In this paper, we have shown that butyl paraben had an adverse effect on the male mouse reproductive system and that it damaged the late steps of spermatogenesis in the testis. Butyl paraben was administered to 4-week-old Crj:CD-1 mice assigned to groups of eight animals, at doses of 0.01%, 0.10%, and 1.00% in the diet for 10 weeks. The average butyl paraben intake from the calculated food consumption was 14.4+/-3.60, 146+/-35.9, and 1504+/-357 mg/kg per day for the 0.01%, 0.10%, and 1.00% dietary butyl paraben groups, respectively. There were no treatment-related effects of butyl paraben on the liver, ventral prostates, seminal vesicles, and preputial glands (both in terms of absolute weight and relative to body weight) in any of the study groups. Both the absolute and relative weights of the epididymides were significantly higher in 1.00% group when compared with controls. A dose-dependent decrease of both round and elongated spermatid counts in stages VII-VIII seminiferous tubules was observed, and the elongated spermatid counts were significantly lower in all of the treated groups. The numbers of spermatogonia and spermatocytes did not differ from control values. The serum testosterone concentration decreased in a dose-dependent fashion and was significant at 1.00%. These data demonstrated that butyl paraben can exert an adverse effect on the male reproductive system at doses that are well below those of the accepted daily intake (ADI) in Japan.

Analysis of Variance↗

PubMed2005

The effects of parabens on the mechanosensitive channels of E. coli.

Parabens are alkyl esters of p-hydroxybenzoic acid used as preservatives in a wide range of food, pharmaceutical, and cosmetic products. Despite their common use for over 50 years, their mechanism of action is still unclear. In this study we examined the effects of ethyl and propyl paraben, on gating of the E. coli mechanosensitive channel of large conductance (MscL) reconstituted into azolectin liposomes. We found that propyl and ethyl paraben spontaneously activate MscL. Moreover, the addition of propyl paraben caused an increase in MscL activity and the lowering of p(1/2), the pressure at which the MscL was opened 50% of the time, the DeltaG(o), the free energy required to open the MscL, and the parameter alpha, which describes the channel sensitivity to pressure. In addition, in silico studies showed that propyl paraben binds to the channel gate of the MscL. The mechanosensitive channel of small conductance was also found to be spontaneously activated by parabens. In summary, our study indicates that one of the previously unidentified mechanisms of action of parabens as antimicrobial agents is via an interaction with the mechanosensitive channels to upset the osmotic gradients in bacteria.

Bacterial Proteins↗

PubMed2002

Effects of propyl paraben on the male reproductive system.

Parabens are p-hydroxybenzoic acid ester compounds widely used as preservatives in foods, cosmetics, toiletries and pharmaceuticals. These compounds exert a weak estrogenic activity as determined by in vitro estrogen receptor assay and in vivo uterotrophic assay. In a previous study, it was demonstrated by the present author that exposure of post-weaning mammals to butyl paraben adversely affects the secretion of testosterone and the function of the male reproductive system. In the present study, it is shown that propyl paraben also adversely affects the hormonal secretion and the male reproductive functions. Propyl paraben was administered to 3-week-old rats which were divided into four groups of eight animals each, at doses of 0.00, 0.01, 0.10 and 1.00% with the AIN93G modified diet. At the end of 4 weeks, the rats were sacrificed by decapitation and the weights of testes, epididymides, prostates, seminal vesicles and preputial glands were determined. There were no treatment-related effects of propyl paraben on the organ weights in any of the study groups. The cauda epididymal sperm reserves and concentrations decreased in a dose-dependent manner and the difference was significant at dose of 0.10% and above. Daily sperm production and its efficiency in the testis of all groups receiving propyl paraben significantly decreased. The serum testosterone concentration decreased in a dose-dependent manner and the decrease was significant in the group that received the highest dose. The exposure level at which this effect was observed is the same as the upper-limit acceptable daily intake (10 mg/kg body weight/day) of parabens in the European Community and Japan.

Animals↗

PubMed1999

The effect of parabens in a mouthwash and incorporated into a sustained release varnish on salivary bacteria.

OBJECTIVES: The purpose of this study was to evaluate the antimicrobial efficacy of parabens, in a mouthwash and in a slow release device, against cariogenic bacteria in the oral cavity. METHODS: Parabens were formulated in a mouthwash or in a topical slow release varnish preparation. In two separate studies, volunteers were asked to use the mouthwash or the slow release varnish applied in a personal night guard device. The levels of mutans streptococci (MS), Lactobacilli (LB) and total cultivated bacteria were measured before and after using the mouthwash or the slow release varnish. RESULTS: The mouthwash containing parabens had a minor and a short-term effect on MS and LB counts in human saliva. The use of slow release varnish containing parabens, applied in a night guard, had a prolonged antibacterial effect on both MS and LB counts. CONCLUSIONS: Parabens in a mouthwash had little effect on oral bacteria counts; however, paraben in the slow release device had a significant and an extended effect in reducing oral bacteria. Although substantial reductions in oral bacterial counts were recorded after the use of parabens in a slow release device, this effect could probably be enhanced by an improved pharmaceutical formulation.

Administration, Topical↗

PubMed2000

Allergic contact dermatitis caused by parabens: 2 case reports and a review.

Parabens, methyl, ethyl, propyl, benzyl, and butyl, are the most common preservatives in use today. They are the alkyl esters of p-hydroxybenzoic acid and are used extensively because they are relatively nonirritating and nontoxic and offer good antimicrobial coverage. Testing for paraben allergen can be done by patch testing. Two cases of allergic contact dermatitis (ACD) to parabens are used to discuss the background of parabens, their allergenicity, patch testing issues, and several "paraben paradoxes." Although ACD to parabens has been reported, given the widespread use, it is relatively uncommon. Because of their low rate of allergenicity and their favorable preservative profile and efficacy, parabens remain the number one preservative in use.

Adult↗

PubMed1995

Effect of 2-hydroxypropyl-beta-cyclodextrin on percutaneous absorption of methyl paraben.

A potential use of 2-hydroxypropyl-beta-cyclodextrin (HP-beta-CyD) to solubilize methyl paraben and to suppress its percutaneous absorption was examined, and compared with nonionic surfactant HCO-60. HP-beta-CyD significantly increased the solubility of methyl paraben in water, where the apparent 1:1 stability constant of the soluble complex was determined to be 2150 M-1. The in-vitro cutaneous permeability of methyl paraben through an isolated skin of hairless mouse was suppressed by HP-beta-CyD, thus promoting the bioconversion of methyl paraben to the less toxic metabolite, p-hydroxybenzoic acid (p-HBA) in the epidermis. These effects of HP-beta-CyD were greater than those of HCO-60. HP-beta-CyD (2% w/v) reduced the in-vivo percutaneous absorption of methyl paraben by 66% 24 h after the topical application of a solution containing [14C]methyl paraben to hairless mouse skin. Additionally, the percutaneous absorption of [14C]HP-beta-CyD was confirmed to be extremely low. These results suggest that HP-beta-CyD is useful in liquid preparations of methyl paraben for topical application.

2-Hydroxypropyl-beta-cyclodextrin↗

PubMed2006

Paraben transport and metabolism in the biomimetic artificial membrane permeability assay (BAMPA) and 3-day and 21-day Caco-2 cell systems.

Noncellular and cellular in vitro models for predicting intestinal absorption were used to investigate the transport and metabolism of parabens. The biomimetic artificial membrane permeability assay (BAMPA) membrane was constructed by impregnating a lipid solution on a hydrophobic filter. Caco-2 cells at passage numbers 65 to 80 were cultured in either the accelerated 3-day Biocoat system or the standard 21-day Transwell cell culture system. Paraben transport across the BAMPA system showed a parabolic relationship. The lowest log P (p-hydroxybenzoic acid) and highest log P compounds (heptyl and octyl parabens) had apparent permeabilities (Papp) less than 1.0 x 10(-6) cm/s and Papp was maximal at approximately 8.5 x 10(-6)cm/s for the intermediate log P (ethylparaben) compound. With the Biocoat, a similar parabolic relationship was found. In the 21-day Caco-2 cells, the parabens were metabolized by esterases at to p-hydroxybenzoic acid. In conclusion, the in vitro models added complementary insight into the absorption process, such as the transport route, intrinsic permeability, and extent of metabolism of the parabens. This study indicated that presystemic metabolism of orally ingested parabens to the p-hydroxybenzoic acid in the intestine may limit systemic exposure to alkyl-paraben esters in vivo.

Biological Transport↗

PubMed2005

Decrease in skin permeation and antibacterial effect of parabens by a polymeric additive, poly(2-methacryloyloxyethyl phosphorylcholine-co-butylmetacrylate).

The inhibitory effect of poly(2-methacryloyloxyethyl phosphorylcholine-co-butylmetacrylate) (PMB) on the in vitro skin permeation of p-hydroxybenzoic acid and its esters (parabens; methylparaben, ethylparaben, n-propylparaben and n-butylparaben) as model compounds was evaluated. Solubility of the parabens in distilled water was increased by addition of PMB, and the increasing ratio was dependent on the concentration of PMB. The increment of the ratio was more marked in lipophilic parabens than hydrophilic ones. Skin permeability of parabens from their aqueous suspensions was decreased by addition of PMB, and the decreasing ratio was dependent on the PMB concentration. Then, antibacterial effect of parabens of their aqueous solutions was determined with and without PMB by measuring minimum inhibitory concentration (MIC) against E. coli and S. aureus. As results, MIC and antibacterial effect were increased and decreased, respectively, by addition of PMB. The contribution of PMB was more marked in butylparaben than methylparaben. These decreases in skin permeation and antibacterial effect of parabens by PMB are probably due to a higher solubility in water and a lower partition to the skin and bacterial membranes of parabens by addition of PMB.

Animals↗

PubMed1996

Hydrolysis of parabenes by extracts from differing layers of human skin.

We could distinguish four carboxylesterases capable of hydrolyzing 4-hydroxy-benzoic acid esters in human skin and subcutaneous fat tissue. The highest specific activities were found in an extract from subcutaneous fat tissue. The most prominent esterase of this tissue prefers the methyl ester of 4-hydroxybenzoic ester (methyl parabene). Its activity decreases with increasing chain length of the alcohol moiety of the parabenes. The existence of a second parabene esterase in subcutaneous fat is concluded from organophosphate inhibition characteristics. Another prominent parabene esterase was characterized in extracts from transformed keratinocytes. It prefers butyl parabene and its activity decreases with decreasing chain length of the alcohol moiety. The fourth parabene esterase is an enzyme of blood which contaminates the tissue extracts used here. All of the tissue extracts were active at pH 8.0, no parabene hydrolyzing activity could be demonstrated at pH 5.0.

Carboxylic Ester Hydrolases↗

PubMedDate not supplied

Significance of the detection of esters of p-hydroxybenzoic acid (parabens) in human breast tumours.

This issue of Journal of Applied Toxicology publishes the paper Concentrations of Parabens in Human Breast Tumours by Darbre et al. (2004), which reports that esters of p-hydroxybenzoic acid (parabens) can be detected in samples of tissue from human breast tumours. Breast tumour samples were supplied from 20 patients, in collaboration with the Edinburgh Breast Unit Research Group, and analysed by high-pressure liquid chromatography and tandem mass spectrometry. The parabens are used as antimicrobial preservatives in underarm deodorants and antiperspirants and in a wide range of other consumer products. The parabens also have inherent oestrogenic and other hormone related activity (increased progesterone receptor gene expression). As oestrogen is a major aetiological factor in the growth and development of the majority of human breast cancers, it has been previously suggested by Darbre that parabens and other chemicals in underarm cosmetics may contribute to the rising incidence of breast cancer. The significance of the finding of parabens in tumour samples is discussed here in terms of 1). Darbre et al's study design, 2). what can be inferred from this type of data (and what can not, such as the cause of these tumours), 3). the toxicology of these compounds and 4). the limitations of the existing toxicology database and the need to consider data that is appropriate to human exposures.

Breast Neoplasms↗

PubMed1994

The esters of p-hydroxy-benzoate (parabens) inhibit the release of lysosomal enzymes by mitogen-stimulated peripheral human lymphocytes in culture.

An in vitro test was set up to assess the release of lysosomal enzymes from cells and the effect on this process of the commonly used preservatives, parabens. Human peripheral lymphocytes, cultivated in vitro for 24 h in the presence or absence of phytohaemagglutinin (PHA; 5 mg/l), were used. After 1 day of incubation, PHA treatment caused an increased release (from 220 to 500%) of the lysosomal enzymes N-acetyl-beta-D-glucosaminidase, beta-D-glucuronidase, alpha-L-fucosidase and alpha-D-galactosidase. This enhancement was analytically reliable, and detectable with 1-5 micrograms of cell protein. Leakage of lactate dehydrogenase (LDH) underwent only a 20% increase on PHA treatment, indicating that the increased release of lysosomal enzymes was presumably due to secretion, not to cell damage. In PHA-stimulated lymphocytes, methyl-, ethyl-, propyl- and butyl-parabens caused a concentration-dependent diminution of the secretion of lysosomal enzymes. Butyl-paraben appeared to be the most potent inhibitor, causing a 45-50% inhibition at 0.06 mmol/l. With the other parabens, the inhibitory effect became statistically significant at about 0.25 mmol/l for alpha-L-fucosidase and alpha-D-galactosidase, and at 0.5 mmol/l for N-acetyl-beta-D-glucosaminidase and beta-D-glucuronidase. At 1 mmol/l inhibition was greater than 50% for all the enzymes and was more marked with the propyl derivative. Parabens did not influence the release of LDH, suggesting that they affected particularly the secretion of lysosomal enzymes. This supports the hypothesis that parabens are capable of affecting cellular function at concentrations which are likely to be reached in blood or tissues under conditions of common use.

Acetylglucosaminidase↗

PubMed2006

Quantification of the urinary concentrations of parabens in humans by on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry.

Parabens (alkyl esters of p-hydroxybenzoic acid) are widely used as antimicrobial preservatives in cosmetic products, pharmaceuticals, and food processing. However, weak estrogenicity of some parabens has been revealed from several studies. Human exposure to parabens may be assessed by measuring the conjugated or free species of these compounds or their metabolites in urine. We have developed a method using on-line solid phase extraction-high performance liquid chromatography-isotope dilution tandem mass spectrometry with peak focusing to measure the urinary concentrations of methyl, ethyl, propyl, n- and iso- butyl, and benzyl parabens. This method has good reproducibility and accuracy with detection limits for all analytes below 0.2ng/mL in 100microL of urine, and permits quick and accurate analysis of a large number of samples in epidemiologic studies for assessing the prevalence of human exposure to parabens. Using this method, we detected methyl, ethyl, and propyl parabens, mostly as conjugated species, in 22 urine samples collected from anonymous adults.

Calibration↗

PubMed2004

Propyl paraben inhibits voltage-dependent sodium channels and protects cardiomyocytes from ischemia-reperfusion injury.

The effects of propyl paraben, an antimicrobial preservative, on voltage-dependent sodium current and myocardial ischemia-reperfusion injury were investigated in isolated adult rat cardiomyocytes. Whole cell voltage-clamp recording showed that propyl paraben reversibly blocked the voltage-gated sodium channel both in concentration- and voltage-dependent manners. Propyl paraben (500 microM but not 100 microM) significantly shifted the steady-state inactivation of the sodium channel toward the hyperpolarizing direction at the V(1/2) point. Consistent with the above result, the propidium iodide (PI) uptake test revealed that pretreatment with 500 microM but not 100 microM of propyl paraben significantly reduced cell death induced by 45 min of sustained ischemia followed by 15 h of reperfusion (42.37 +/- 7.01% of cell viability in control and 71.05 +/- 7.06% in the propyl paraben group), suggesting that propyl paraben can protect myocytes from ischemia-reperfusion injury. These results indicate a possible correlation between the inhibition of sodium current and cardioprotection against ischemia-reperfusion injury.

Animals↗

PubMed1992

Kinetic evaluation of claimed synergistic paraben combinations using a factorial design.

The antimicrobial effects of methyl and propyl parabens are investigated, with Escherichia coli as test organism, with a view to determining whether the parabens act synergistically. At appropriate concentrations, the parabens killed E. coli cells according to first order kinetics and the bactericidal effects were quantified by the first order kill rate constants. Combinations of methyl or propyl parabens, at concentrations which slow down or inhibit bacterial growth when used singly, produced definite kill. In this sense, the parabens are therefore synergistic since in combination they produce an effect which is not observed when they are used singly. This effect is not true synergism as shown by the results of our experiments with a factorial design. Analysis of variance indicated no significant interaction between the two parabens.

Analysis of Variance↗

PubMed2002

prbA, a gene coding for an esterase hydrolyzing parabens in enterobacter cloacae and Enterobacter gergoviae strains.

The new gene prbA encodes an esterase responsible for the hydrolysis of the ester bond of parabens in Enterobacter cloacae strain EM. This gene is located on the chromosome of strain EM and was cloned by several PCR approaches. The prbA gene codes for an immature protein of 533 amino acids, the first 31 of which represent a proposed signal peptide yielding a mature protein of a putative molecular mass of 54.6 kDa. This enzyme presents analogies with other type B carboxylesterases, mainly of eukaryotic origin. The cloning and expression of the prbA gene in a strain of Escherichia coli previously unable to hydrolyze parabens resulted in the acquisition of a hydrolytic capacity comparable to the original activity of strain EM, along with an increased resistance of the transformed strain to methyl paraben. The presence of homologues of prbA was tested in additional ubiquitous bacteria, which may be causative factors in opportunistic infections, including Enterobacter gergoviae, Enterobacter aerogenes, Pseudomonas agglomerans, E. coli, Pseudomonas aeruginosa, and Burkholderia cepacia. Among the 41 total strains tested, 2 strains of E. gergoviae and 1 strain of Burkholderia cepacia were able to degrade almost completely 800 mg of methyl paraben liter(-1). Two strains of E. gergoviae, named G1 and G12, contained a gene that showed high homology to the prbA gene of E. cloacae and demonstrated comparable paraben esterase activities. The significant geographical distance between the locations of the isolated E. cloacae and E. gergoviae strains suggests the possibility of an efficient transfer mechanism of the prbA gene, conferring additional resistance to parabens in ubiquitous bacteria that represent a common source of opportunistic infections.

Amino Acid Sequence↗