Polycyclic aromatic hydrocarbons in teas using QuEChERS and HPLC-FLD.

Polycyclic aromatic hydrocarbons (PAHs) are food-processing contaminants considered to be carcinogenic and genotoxic. Due to its drying process stage, teas may be contaminated with PAHs. The aim of the study was to validate an analytical method involving QuEChERS and HPLC-FLD for the determination of PAH4 in teas and evaluate the contamination levels in 10 different types of teas from Brazil. Recoveries varied from 54% to 99% and relative standard deviations from 1% to 21%. Limits of detection and quantification were from 0.03 to 0.3 µg/kg and 0.1 to 0.5 µg/kg, respectively. Mate tea presented the highest PAH levels, with PAH4 varying from 194 to 1795 µg/kg; followed by black (1.8-186 µg/kg), white (24-119 µg/kg), and green teas (3.1-92 µg/kg). Teas with lowest PAH4 were strawberry, lemongrass, peppermint, and boldo. Only trace levels of PAHs were detected in tea infusions, so apparently it would not affect PAH intake by Brazilian population.

Metabolism of an Alkylated Polycyclic Aromatic Hydrocarbon 5-Methylchrysene in Human Hepatoma (HepG2) Cells.

Exposure to polycyclic aromatic hydrocarbons (PAHs) in the food chain is the major human health hazard associated with the Deepwater Horizon oil spill. C1-chrysenes are representative PAHs present in the crude oil and have been detected in contaminated sea food in amounts that exceed their permissible safety thresholds. We describe the metabolism of the most carcinogenic C1-chrysene regioisomer, 5-methylchrysene (5-MC), in human HepG2 cells. The structures of the metabolites were identified by HPLC-UV-fluorescence detection and LC-MS/MS. 5-MC-tetraol, a signature metabolite of the diol-epoxide pathway, was identified as reported previously. Novel O-monosulfonated-5-MC-catechol isomers and O-monomethyl-O-monosulfonated-5-MC-catechol were discovered, and evidence for their precursor ortho-quinones was obtained. The identities of O-monosulfonated-5-MC-1,2-catechol, O-monomethyl-O-monosulfonated-5-MC-1,2-catechol, and 5-MC-1,2-dione were validated by comparison to authentic synthesized standards. Dual metabolic activation of 5-MC involving the formation of bis-electrophiles, i.e., a mono-diol-epoxide and a mono-ortho-quinone within the same structure, bis-diol-epoxides, and bis-ortho-quinones is reported for the first time. Evidence was also obtained for minor metabolic conversion of 5-MC to form monohydroxylated-quinones and bis-phenols. The identification of 5-MC-tetraol, O-monosulfonated-5-MC-1,2-catechol, O-monomethyl-O-monosulfonated-5-MC-1,2-catechol, and 5-MC-1,2-dione supports metabolic activation of 5-MC by P450 and AKR isozymes followed by metabolic detoxification of the ortho-quinone through interception of redox cycling by COMT and SULT isozymes. The major metabolites, O-monosulfonated-catechols and tetraols, could be used as biomarkers of human exposure to 5-MC resulting from oil spills.

Semi-preparative gas chromatographic separation of all-trans-perhydrotriphenylene enantiomers on a chiral cyclodextrin stationary phase.

Enantiomers of all-trans-perhydrotriphenylene (PHTP) were separated by gas chromatography using heptakis(6-O-tert.-butyldimethylsilyl-2,3-di-O-methyl)-beta-cyclodextrin (TBDMS-beta-CD) as the chiral selector. Conditions for semi-preparative separations were established using a 2 m x 2 mm I.D. packed column and subsequently extended to a 1.8 m x 4 mm I.D. column which enabled separations on a mg scale. The column packing was TBDMS-beta-CD dissolved in SE-54 coated on Chromosorb P AW-DMCS 80-100 mesh. Optimization of the chromatographic conditions (oven temperature, carrier gas flow, and column load) with respect to better efficiency and peak retention resulted in a system capable of separating up to 10 mg of the racemate per day. Purities of separated enantiomers were determined by capillary gas chromatography. Yields and purities of the fractions obtained by single- and double-step separations are compared. Highly enriched enantiomers with purities of up to 99.6% (99.2% ee) were obtained by a single separation step.

Selective covalent binding of the active sulfate ester of the carcinogen 5-(hydroxymethyl)chrysene to the adenine residue of calf thymus DNA.

5-(Hydroxymethyl)chrysene (5-HCR) sulfate, an active metabolite of the carcinogen 5-HCR, bound significantly in a covalent manner to the purine bases of calf thymus DNA through its 5-methylene carbon with loss of a sulfate anion when incubated at pH 7.4 and 37 degrees C. From the DNA were isolated two purine base adducts by high-pressure liquid chromatography, and they were identified as N6-[(chrysen-5-yl)methyl]adenine and N2-[(chrysen-5-yl)methyl]guanine with the corresponding synthetic specimens. The purine base adducts, appearing in the ratio 1 to 27 for guanine to adenine in the chromatogram, accounted for about 60% of the total covalent binding of 5-HCR sulfate to the DNA. 5-HCR sulfate also reacted specifically with the exocyclic amino groups of the purine bases of 2'-deoxyadenosine 5'-phosphate and 2'-deoxyguanosine 5'-phosphate at much lower rates than did with those of calf thymus DNA. Denaturing the DNA by heating followed by rapid cooling, covalent binding of 5-HCR sulfate to it markedly decreased with the increasing ratio of N2-guanine to N6-adenine adducts (1:3.6). These results strongly suggest that secondary structure of DNA has an influence on the covalent binding of 5-HCR sulfate and that intercalation of the sulfate ester into DNA base pairs plays an important role in its preferential binding to N6 of the adenine residue of native DNA.