Selective determination of trace 17β-estradiol in dairy and meat samples by molecularly imprinted solid-phase extraction and HPLC

Molecularly imprinted solid-phase extraction (MISPE) combined with HPLC were used to detect trace 17β-estradiol (E2) in different dairy and meat samples. E2 imprinted mono-dispersed microspheres prepared by modified precipitation polymerisation method were used as MISPE sorbents. Under optimum MISPE and HPLC conditions, trace (0.116–0.461 nmol kg⁻¹) E2 in different dairy and meat samples can be detected accurately using UV detector when large amount of sample (500 g) was analysed. Recoveries of E2 from spiked (0.1–5 nmol kg⁻¹) milk, yogurt, beef, pork and chicken were higher than 74.18%, 71.92%, 67.21%, 64.20% and 65.93%, respectively with RSDs less than 8.38%. MISPE can enrich E2 selectively, which is helpful to have better HPLC separation and higher recoveries than C18 SPE. MISPE combined with HPLC-UV are reliable methods to determine trace E2 in dairy and meat samples with high accuracy and repeatability.  

Selectivity of molecularly imprinted solid phase extraction for sterol compounds

MIPs (molecularly imprinted polymers) for 17β-estradiol were prepared using 2-(trifluoromethyl) acrylic acid (TFMAA) as functional monomer and trimethylolpropane trimethacrylate (TRIM) as cross-linker by precipitation polymerisation. Data from HPLC system were calculated, and separation properties of several MIPs were reported. MISPEs (molecularly imprinted solid phase extractions) were performed with MIPs as sorbent, and absorption properties of the MISPEs prepared by UV irradiation initiating polymerisation at a ratio of 1/4 (17β-estradiol/TFMAA) for 17α-estradiol, 17β-estradiol, 4-androstene-3, 17-dione and progesterone investigated by detecting filtrates at each stage of sampling, washing and elution. Elution trials proved that addition acid or alkali reagents might affect retention of the MISPE and CSPE (control/no molecularly imprinted solid phase extraction) for 17β-estradiol. A competition test implicates that the MISPE has the strongest specific retention and enrichment for progesterone. In the actual experiment for 17β-estradiol with extracting solution of milk powder as samples, the MISPE showed better selectivity and enrichment property than C18 and CSPE, and the recovery on the MISPE was up to 85.5%.  

Short communication: Heat treatment and souring do not affect milk estrone and 17β-estradiol concentrations

The aim of our study was to establish whether heat treatment and souring of milk affect its estrone (E1) and 17β-estradiol (E2) concentrations. Milk samples were collected from 10 Holstein cows in late pregnancy. Concentrations of E1 and E2 were measured in milk samples that were previously heated to 70 and 95°C for 5 min. Additionally, E1 and E2 concentrations were determined in the same milk samples after 2 d of spontaneous souring at room temperature, and these samples were compared with E1 and E2 levels in raw, unprocessed milk. Concentrations of both hormones were determined by commercial ELISA kits. Concentrations of E1 in unprocessed and processed milk (milk heated to 70 and 95°C and soured milk) were (mean ± SE) 47.25 ± 4.16, 44.84 ± 3.47, 41.00 ± 4.55, and 44.92 ± 3.91 pg/mL, respectively. Concentrations of E2 in the same milk samples were 36.11 ± 10.01, 32.46 ± 9.88, 31.78 ± 9.56, and 31.43 ± 8.00 pg/mL, respectively. Concentrations of E1 and E2 in heat-treated milk did not differ significantly from those in unprocessed milk. Similarly, E1 and E2 concentrations in soured milk did not differ significantly from those in unprocessed milk samples. These results indicate that E1 and E2 are stable in milk and that milk processing (heating and souring) does not influence their degradation. Therefore, E1 and E2 concentrations are expected to be similar between commercial full-fat milk and the raw milk from which it was produced.  

HPLC法测定鸭胚蛋中游离性激素的研究

研究确立了樱桃谷SM3型鸭胚蛋中的游离性激素17β-雌二醇、丙酸睾酮的测定方法。用甲醇提取鸭胚蛋匀浆液中的17β-雌二醇、丙酸睾酮,再经高效液相色谱仪进行定性、定量分析。该方法线性范围为0.05～3.50μg/mL,标准曲线线性关系良好,其回归方程和相关系数分别为17β-雌二醇y=2278.8x+31.46,R~2= 0.999 9,丙酸睾酮y=925.32x-14.812,R~2=0.9996;检测限为17β-雌二醇2.7ng,丙酸睾酮3.4ng;回收率在89.1%～94.6%之间,相对标准偏差<2.3%。该方法操作简便快捷,有较好的回收率和准确度,适合大量的检测胚胎类保健食品中的游离性激素。  

Confirmation of the progesterone receptor as an efficient marker of treatment with 17β-estradiol in veal calves

Under current European Union legislation the use of anabolic steroids in food-producing livestock is banned because of their long-term adverse effects on human health. We examined the expression profile of the immunohistochemical marker progesterone receptor in veal calves’ sex accessory glands following experimental administration of anabolic compounds. The aim was to confirm the accuracy of the immunohistochemical approach in the detection of the over-expression of the progesterone receptor induced by the administration of sexual steroids at low levels (17β-estradiol and nandrolone alone or in combination). A total of 217 male veal calves were randomly divided into four groups: group A (104 calves) treated with 17β-estradiol (5 mg/head; 4 weekly injections); group B (20 calves) treated with nandrolone (50 mg/head; 4 weekly injections); group C (20 calves) treated with the association of the two steroids (5 mg estradiol + 50 mg nandrolone; 4 weekly injections); and group K (73 calves) kept as a control. All the sexual accessory glands were collected at the slaughterhouse (15 days after the last administration) and subjected to immunohistochemical staining with anti-progesterone receptor antibody. All the calves treated with 17β-estradiol alone or in association with nandrolone (groups A and C) showed strong positivity, while nandrolone-treated calves and controls (groups B and K) gave negative results to the immunohistochemical investigation. The statistical analysis showed that the progesterone receptor is a significant predictor of 17β-estradiol treatment alone or in association with nandrolone (p < 0.001): the immunohistochemical study resulted in 100% sensitivity (CI = 95%: 97.1–100%) and specificity (CI = 95%: 95.1–100%) for prostate and 99% sensitivity (CI = 95%: 95.6–100%) and 100% specificity (CI = 95%: 95.1–100%) for bulbo-urethral glands. The data confirm that this innovative biological approach offers a reliable tool to enhance the efficacy of the histological test to detect illegal treatments with estrogens alone or in association with androgens.  

Estrone and 17β-estradiol concentrations in pasteurized-homogenized milk and commercial dairy products

Some individuals fear that estrogens in dairy products may stimulate growth of estrogen-sensitive cancers in humans. The presence of estrone (E₁) and 17β-estradiol (E₂) in raw whole cow's milk has been demonstrated. The objectives of this study were to determine if pasteurization-homogenization affects E₂ concentration in milk and to quantify E₁ and E₂ concentrations in commercially available dairy products. The effects of pasteurization-homogenization were tested by collecting fresh raw milk, followed by pasteurization and homogenization at 1 of 2 homogenization pressures. All treated milks were tested for milk fat globule size, percentages of milk fat and solids, and E₂ concentrations. Estrone and E₂ were quantified from organic or conventional skim, 1%, 2%, and whole milks, as well as half-and-half, cream, and butter samples. Estrone and E₂ were quantified by RIA after organic solvent extractions and chromatography. Pasteurization-homogenization reduced fat globule size, but did not significantly affect E₂, milk fat, or milk solids concentrations. Estrone concentrations averaged 2.9, 4.2, 5.7, 7.9, 20.4, 54.1 pg/mL, and 118.9 pg/g in skim, 1%, 2%, and whole milks, half-and-half, cream, and butter samples, respectively. 17β-Estradiol concentrations averaged 0.4, 0.6, 0.9, 1.1, 1.9, 6.0 pg/mL, and 15.8 pg/g in skim, 1%, 2%, whole milks, half-and-half, cream, and butter samples, respectively. The amount of fat in milk significantly affected E₁ and E₂ concentrations in milk. Organic and conventional dairy products did not have substantially different concentrations of E₁ and E₂. Compared with information cited in the literature, concentrations of E₁ and E₂ in bovine milk are small relative to endogenous production rates of E₁ and E₂ in humans.  

17Beta-estradiol and estrone concentrations in plasma and milk during bovine pregnancy

Estrone (E₁) and 17β-estradiol (E₂) are present in milk, but the mechanism(s) that regulate their appearance in milk are not known. The objectives of this study were to determine the impact of stage of pregnancy on the concentrations of E₁ and E₂ in plasma and milk and to determine the correlations between plasma and milk E₁ and E₂ and with milk components throughout pregnancy. Blood and milk samples were collected from 13 cows every 28 d throughout pregnancy. The E₁ and E₂ were quantified in plasma and milk using RIA after organic solvent extractions and Sephadex LH-20 column chromatography. Plasma E₁ concentrations averaged 0.8, 16.9, and 41.8 pg/mL in trimesters 1, 2, and 3, respectively. The respective E₁ concentrations in milk averaged 0.6, 7.9, and 27.1 pg/mL. The E₂ concentrations in plasma averaged 0.5, 0.9, and 2.0 pg/mL; milk E₂ averaged 0.3, 0.9, and 5.0 pg/mL. Plasma and milk E₂ concentrations were greater in trimester 3 compared with trimesters 1 and 2. The E₁ concentrations in milk were significantly correlated with plasma E₁ concentrations (r = 0.77), percentage of milk fat (r = 0.50), and milk yield (r = −0.43). The E₂ concentrations in milk were significantly correlated with plasma E₂ concentrations (r = 0.93), percentage of milk protein (r = 0.63), and milk yield (r = −0.57). The milk-to-plasma ratio of E₂ increased from 0.4 during trimester 1 to 2.2 in trimester 3, which suggested that the mechanism(s) regulating the appearance of E₂ in milk may change over the course of pregnancy.