Human metabolism and urinary excretion kinetics of di-n-butyl adipate (DnBA) after oral and dermal administration in three volunteers.

Di-n-butyl adipate (DnBA) is used as a plasticizer and in various consumer products (e.g. personal care products) replacing, in part, the endocrine disruptor di-n-butyl phthalate (DnBP). We provide quantitative in vivo data on human DnBA metabolism and excretion after oral dose (105-185 µg/kg bw) and dermal application to three volunteers each as a tool for exposure and risk assessment. Complete and consecutive urine samples were collected for two (oral) and four days (dermal), respectively, and analyzed for the metabolites mono-n-butyl adipate (MnBA), 3- and tentative 4-hydroxy-mono-n-butyl adipate (3OH-MnBA, 4OH-MnBA), and 3-carboxy-mono-n-propyl adipate (3cx-MnPrA), as well as the hydrolysis product adipic acid (AA) using stable isotope dilution quantification. Metabolites were excreted within 24 h after oral dose with one or two concentration maxima at 0.8-3.0 h (n = 3) and 4.8-6.3 h (n = 2). AA was the major but unspecific metabolite with urinary excretion fractions (FUEs) of 14-26 %. Mean FUEs (range) of 3cx-MnPrA, MnBA, 3OH-MnBA, and tentative 4OH-MnBA were low, but consistent between volunteers (0.47 % (0.35-0.63 %), 0.079 % (0.065-0.091 %), 0.012 % (0.006-0.016 %), and 0.005 % (0.002-0.009 %), respectively). MnBA and 3OH-MnBA seem to be suitable, specific exposure biomarkers for DnBA, whereas 3cx-MnPrA and 4OH-MnBA seem to originate also from other, unknown sources not related to DnBA. Compared to the oral study, metabolite excretion in the dermal study was delayed and MnBA excretion was somewhat higher compared to the oxidized metabolites. Based on urinary concentrations and the above excretion fractions, calculated uptakes in the dermal study did not exceed the adipate ester ADI of 5 mg/(kg bw*day).

Metabolism and urinary excretion kinetics of di(2-ethylhexyl) adipate (DEHA) in four human volunteers after a single oral dose.

Di(2-ethylhexyl) adipate (DEHA) is used as a substitute for the reprotoxic phthalate plasticizer di(2-ethylhexyl) phthalate (DEHP). This study reports the first quantitative data on human in vivo DEHA metabolism and urinary metabolite excretion with the aim of providing tools for DEHA exposure and risk assessments. After DEHA was administered to four healthy volunteers (107-164 µg/kg body weight (bw)), urine samples were continuously and completely collected for 48 h and analyzed for the specific oxidized monoester metabolites mono-2-ethyl-5-hydroxyhexyl adipate (5OH-MEHA), mono-2-ethyl-5-oxohexyl adipate (5oxo-MEHA), and mono-5-carboxy-2-ethylpentyl adipate (5cx-MEPA), as well as for the non-specific hydrolysis product adipic acid (AA) using stable isotope dilution analysis. AA was confirmed as a major (urinary excretion fraction (FUE): 10-40%), yet non-specific DEHA metabolite. 5cx-MEPA was the major specific DEHA metabolite with an FUE of 0.20% (range: 0.17-0.24%). FUEs for 5OH-MEHA and 5oxo-MEHA were 0.07% (0.03-0.10%) and 0.05% (0.01-0.06%), respectively. The three specific metabolites were excreted with two concentration maxima (tmax1 = 1.5-2.3 h, tmax2 = 3.8-6.4 h). Elimination half-lives (t1/2, calculated after the second tmax) for 5cx-MEPA were calculated between 2.1-3.8 h. The majority (98-100%) of metabolites was excreted within 24 h. The FUE of 5cx-MEPA was applied to demonstrate its applicability for calculating daily intakes based on urinary metabolite levels from three pilot populations. Daily intakes were generally far below the tolerable daily intake (TDI) for DEHA (300 µg/kg bw/day). The highest daily intake (114 µg/kg bw/day) was calculated in individuals after consuming food that had been wrapped in DEHA containing cling film.

Heparin appended ADH-anionic polysaccharide nanoparticles for site-specific delivery of usnic acid.

The intention of present research work is to formulate usnic acid (UA) loaded heparin modified gellan gum (HAG) nanoparticles (NPs). HAG copolymer based conjugation was synthesized and characterized by 1H NMR and FT-IR spectroscopy. Plain and UA loaded HAG NPs were prepared via nanoprecipitation technique. NPs were typified and further characterized for particle size, polydispersity index, entrapment efficiency, zeta potential, atomic force microscopy, differential scanning calorimetry, X-ray diffraction analysis, and in-vitro release. In-vitro tube formation assay, tumorsphere assay, autophagy assay, DNA cleavage assay, internalization by confocal and FACS based internalization analysis, caspase assay and cell cycle assay were performed for biological activity. Obtained experimental results explored that HAG NPs displayed a sustained release of UA (95.67% in 48 h) compared to gellan gum NPs (96.12% in 8 h). In cytotoxicity studies, UA loaded HAG NPs exhibited an enormous cytotoxic potential against A549 cancer cells. In the in vivo bio-distribution study, using albino rat model the free UA concentration was found 7.09 ±â€¯0.9%, 2.7 ±â€¯1.5%, 7.5 ±â€¯2.1, 9.2 ±â€¯2%, and 6.25 ±â€¯1.3% post two hours of intravenous administration, however, in the case of UA loaded HAG NPs the obtained level was 4.1 ±â€¯1.10, 7.7 ±â€¯1.30%, 2.21 ±â€¯0.29%, 1.85 ±â€¯0.25%, 2.2 ±â€¯0.78%, 2.9 ±â€¯1.21% respectively, in heart, lung, liver, spleen, intestine and kidney. The overall anticancer study and result of internalization deciphered the higher anticancer potential of UA loaded HAG NPs.

In vitro dermal absorption of di(2-ethylhexyl) adipate (DEHA) in a roll-on deodorant using human skin.

In vitro dermal absorption experiments were conducted using a roll-on deodorant that contains 1.56% di(2-ethylhexyl) adipate (DEHA), a plasticizer widely used in consumer products. Human skin specimens were fitted in Bronaugh flow-through Teflon diffusion cells. The diffusion cells were maintained at 32 °C to reflect the skin temperature. Two amounts (low dose: 5 mg of the product; high dose: 100 mg) were applied, in triplicate, each on four different human skins. DEHA was determined in the receiver solution at 6-h intervals, using headspace solid-phase microextraction gas chromatography-mass spectrometry (GC-MS). After 24 h, the experiment was terminated and masses of DEHA in the skin depot, skin wash, and upper and lower chambers of the diffusion cell were determined. A significant portion of applied DEHA, 28% in the low amount application and 34% in the high one, was found in the skin depot. In comparison, only 0.04% and 0.002% of applied DEHA were found in the receiver solutions for the low and high doses, respectively. Under our experimental conditions, an apparent steady-state flux of low DEHA mass penetrating from skin into the receiver solution was observed with a penetration rate of 2.2 ng/cm(2)/h for both the low and high doses. The average mass recovery was 81% for the low dose application and 56% for the high dose.

Correlation of hydrolytic degradation with structure for copolyesters produced from glycolic and adipic acids.

Copolyesters based on glycolic acid (G) combined with adipic acid (A) and ethylene glycol (E) were synthesized in different percentage of molar ratios (A: 100-50% and G: 100%) and their hydrolytic degradation was studied and correlated with their structures. According to the DSC, the production of polyesters leads to the formation of copolyesters and not to mixtures of homopolyesters. The crystallites in the copolyesters mainly consist of continuous sequences of ethylene adipate structural units. The hydrolytic degradation of the polyesters was followed by their weight loss during hydrolysis and by the FTIR spectra of the initial polyesters compared with that of the degraded polyesters at equilibrium. The region between 1142 and 800 cm(-1) can be utilized to evaluate the extent of degradation of polyesters after their hydrolysis. The absorption bands at 1142, 1077 and 850 cm(-1) due to the amorphous region decrease after hydrolysis, whereas those at 972, 901 and 806 cm(-1) due to the crystalline region increase. The experimental data of the hydrolytic degradation were fitted with exponential rise to maximum type functions using two-parameter model, which describes very well mainly the initial part of the degradation, and four-parameter model (containing two exponential terms), which is appropriate for fitting the hydrolytic degradation on the entire time period (including the equilibrium). Furthermore, the kinetics of the hydrolytic degradation of the polyesters for the initial time period based on both models results to similar values of the rate constant, k. The synthesized copolyesters of glycolic acid combined with adipic acid and ethylene glycol are soluble in many common organic solvents opposite to PGA, leading to modified biodegradable polyesters and therefore they can be easily processed.

Toxicity of di(2-ethylhexyl)phthalate (DEHP) and di(2-ethylhexyl)adipate (DEHA) under conditions of renal dysfunction induced with folic acid in rats: enhancement of male reproductive toxicity of DEHP is associated with an increase of the mono-derivative.

F344 male rats were given five consecutive weekly subcutaneous injections of folic acid for induction of chronic renal dysfunction and then di(2-ethylhexyl)phthalate (DEHP) or di(2-ethylhexyl)adipate (DEHA) in the diet at a concentration of 0, 6000 or 25,000 ppm for 4 weeks in order to investigate whether male reproductive toxicity of the two chemicals might be enhanced under conditions of renal disease. Control animals also received DEHP or DEHA in the same manner but without folic acid pretreatment. Decreased testicular weights, seminiferous atrophy with vacuolization of sertoli cells and diminished sperm counts were more prominent in rats given folic acid and then 25,000 ppm DEHP as compared to those exposed to DEHP alone. No such reproductive toxicity was evident in rats given 6000 ppm DEHP or either dose of DEHA. An increased concentration of the mono-derivative of DEHP (mono(2-ethylhexyl)phthalate, MEHP) in the blood, testis and urine was considered relevant to the enhanced reproductive toxicity observed with DEHP.

Sites and mechanisms for uptake of gases and vapors in the respiratory tract.

Inhalation is a common route by which individuals are exposed to toxicants. The air contains a multitude of gases and vapors that are brought into the respiratory tract with each breath. Depending upon the physical and chemical characteristics of the toxicant, the respiratory tract can be considered as a target organ in addition to a portal of entry. Sufficient information is not always available on the fate or effects of an inhaled gas or vapor. Two physiochemical principles, water solubility and reactivity, can be used to predict the site of uptake of gases and vapors in the respiratory tract and potential mechanisms for reaction with respiratory tract tissue and absorption into the blood. Four model compounds, formaldehyde, ozone, dibasic esters, and butadiene are discussed as examples of how knowledge of aqueous solubility and chemical reactivity can help toxicologists predict sites and mechanisms by which inhaled gases and vapors interact with respiratory tract tissues.

Biodegradation of poly(ethylene adipate) microcapsules in physiological media.

Spherical reservoir-type microcapsules fabricated using a water/oil/water (W/O/W) double emulsion technique with solvent evaporation and composed of poly(ethylene adipate) (PEAD) blended with 20% poly-epsilon-caprolactone (PCL II) containing a range of bovine serum albumin (BSA) loadings were incubated in Hank's buffer, pH 7.4, newborn calf serum, 1.5% pancreatin and synthetic gastric juice containing 10% pepsin A over 30 days and their percentage weight loss (PWL) and changes in ultrastructural morphology monitored by gravimetry and stereoscan electron microscopy (SEM) respectively. The greatest PWL from microcapsules was observed after incubation in newborn calf serum (NCS) and pancreatin and decreased in the order NCS > pancreatin > synthetic gastric juice > Hank's buffer. Only microcapsules theoretically loaded with 5-20% BSA and incubated in synthetic gastric juice showed a significant increase in PWL with increasing percentage BSA loading. The structural biodegradation of PEAD microcapsules in both Hank's buffer and synthetic gastric juice was minimal whilst the morphological changes observed during incubation in NCS involved pitting of the membrane, some surface erosion and reduction in diameter, followed by microcapsule membrane disruption and loss of reservoir contents. Biodegradation in pancreatin was associated with surface flaking and loss of large fragments of the microcapsule membrane. Only in NCS and pancreatin, where one would expect to see the effects of enzyme activity in addition to simple ester hydrolysis, did biodegradation proceed to the stage where there was a loss of spherical shape and almost total disruption of the microcapsule structure within 30 days.

Metabolism and pharmacokinetics of deuterium-labelled di-2-(ethylhexyl) adipate (DEHA) in humans.

The metabolism and pharmacokinetics of [2H10]di-2-(ethylhexyl) adipate (DEHA) labelled on the ethyl side-chains was determined in six male volunteers. The dose administered was 46 mg [2H10]DEHA given orally. No parent molecule was found in plasma; however, the metabolite [2H5]2-ethylhexanoic acid (EHA) was detected (mean rate of formation: 1.63 +/- 1.19/hr; mean rate of elimination: 0.42 +/- 0.1/hr). Further oxidative metabolism products were detected in urine; the dominant metabolite identified was EHA present as a conjugate and accounted for an average of 8.6% of the administered dose. [2H5]2-Ethyl-5-hydroxyhexanoic acid, [2H5]2-ethylhexanedioic acid, [2H5]2-ethyl-5-keto-hexanoic acid and [2H5]2-ethylhexanol together accounted for a further 3.5% of the dose. The fate of the remainder was not determined.

Deposition of dibasic esters in the upper respiratory tract of the male and female Sprague-Dawley rat.

Inhalation exposure of the male and female rat to high concentrations of a mixture of the dibasic esters dimethyl succinate (DMS), dimethyl glutarate (DMG), and dimethyl adipate (DMA) results in mild olfactory toxicity. This response is thought to be due to the in situ formation of acidic metabolites via nasal carboxylesterases. The current study was designed to provide inhalation dosimetric information for these vapors. Deposition of DMS, DMG, and DMA was measured in the surgically isolated upper respiratory tracts (URT) of ketamine-xylazine-anesthetized male and female rats under constant velocity flow conditions at a flow rate of 100 ml/min. Deposition of acetone was measured in both genders for comparative purposes. URT deposition efficiencies in excess of 98.3% were observed for DMS, DMG, and DMA in animals exposed to each vapor individually. No gender differences in deposition efficiency were observed for these vapors or for acetone. Deposition of DMS, DMG, and DMA was also measured in animals exposed to all three vapors simultaneously. Deposition efficiency under simultaneous exposure conditions ranged between 97.3 and 98.5%. These values were slightly lower (about 1%) than those obtained under individual exposure conditions (p less than 0.0001). The reduced deposition efficiency may have resulted from competitive inhibition of nasal metabolism due to the simultaneous presence of all three carboxylesterase substrate vapors in nasal tissues. If so, inhalation of dibasic ester vapors would be expected to inhibit the uptake of other carboxylesterase substrate vapors without influencing uptake of vapors which are not substrates for this enzyme. Such was observed in studies using DMS, ethyl acetate (the substrate vapor), and isoamyl alcohol (the nonsubstrate vapor). Specifically, simultaneous exposure to DMS markedly inhibited uptake of ethyl acetate without altering uptake of isoamyl alcohol. Gender differences were not observed in URT deposition of any of the six vapors used in the current study, DMS, DMG, DMA, ethyl acetate, isoamyl alcohol, or acetone, suggesting that gender differences in URT deposition may not be widespread among vapors. The high URT deposition efficiencies of the dibasic esters are consistent with the olfactory toxicity resulting from inhalation exposure to these vapors.

The lateral spread of clobetasol 17-propionate in the stratum corneum in vivo.

Radiolabelled clobetasol 17-propionate in two different bases, propylene glycol (PG) and di-n-butyl adipate (BA), was applied to the backs of 10 normal male volunteers, and the application sites protected. After 8 h samples of stratum corneum (SC) were taken from the application site and an adjacent site, and the level of steroid measured. At the application site there were higher concentrations of the PG formulation at the deeper levels of the SC. At the adjacent sites there were higher concentrations of the BA formulation at the superficial levels. The mean radioactivity at the adjacent sites expressed as a percentage of that at the corresponding application sites (+/- SEM) was 7.8 +/- 5.3% for the BA formulation and 3.0 +/- 2.9% for the PG, (P = 0.0002). Total percentage of the applied dose in the skin adjacent to the application site was 11.7 +/- 6.3% for the BA formulation and 5.3 +/- 5.7% for the PG (P less than 0.0002). Clobetasol 17-propionate, therefore, moves laterally to a greater extent in BA than in PG.