An on-line coupling of nanofibrous extraction with column-switching high performance liquid chromatography - A case study on the determination of bisphenol A in environmental water samples.

Polyamide 6 nanofiber polymers were used as modern sorbents for on-line solid phase extraction (SPE) coupled with liquid chromatography. The on-line SPE system was tested for the determination of bisphenol A in river water samples. Polyamide nanofibers were prepared using needleless electrospinning, inserted into a mini-column cartridge (5 × 4.6mm) and coupled with HPLC. The effect of column packing and the amount of polyamide 6 on extraction efficiency was tested and the packing process was optimized. The proposed method was performed using a 50-µL sample injection followed by an on-line nanofibrous extraction procedure. The influence of the washing mobile phase on the retention of bisphenol A during the extraction procedure was evaluated. Ascentis® Express C18 (10cm × 4.6mm) core-shell column was used as an analytical column. Fluorescence detection wavelengths (λex = 225nm and λem = 320nm) were used for identification and quantification of Bisphenol A in river waters. The linearity was tested in the range from 2 to 500µgL-1 (using nine calibration points). The limits of detection and quantification were 0.6 and 2µgL-1, respectively. The developed method was successfully used for the determination of bisphenol A in various samples of river waters in the Czech Republic (The Ohre, Labe, Nisa, Úpa, and Opava Rivers).

Effect of aqueous extract and anthocyanins of calyces of Hibiscus sabdariffa (Malvaceae) in rats with adenine-induced chronic kidney disease.

OBJECTIVES: The aim of this work was to assess the possible beneficial effects of aqueous extracts of Hibiscus sabdariffa L. calyces and anthocyanins isolated therefrom in an adenine-induced chronic kidney disease (CKD) model. METHODS: Rats were orally given, for 28 consecutive days, either adenine alone or together with either aqueous extract of H. sabdariffa calyces (5 and 10%) or anthocyanins (50, 100 and 200 mg/kg of anthocyanin concentrate). For comparative purposes, two groups of rats were given lisinopril (10 mg/kg). KEY FINDINGS: When either H. sabdariffa aqueous extract or the anthocyanins isolated from it was administered along with adenine, the adverse effects of adenine-induced CKD were significantly lessened, mostly in a dose-dependent manner. The positive effects were similar to those obtained by administration of lisinopril. CONCLUSIONS: The results obtained show that both H. sabdariffa and its anthocyanins could be considered as possible promising safe dietary agents that could be used to attenuate the progression of human CKD. This could have added significance as H. sabdariffa tea is widely consumed in many parts of Africa and Asia and is thus readily available.

Preparation and Validated Analysis of Anthocyanin Concentrate from the Calyces of Hibiscus sabdariffa.

Extracts of Hibiscus sabdarnffa calyces have been shown to have various medicinal properties, some of which have been reported to be due to anthocyanins present in the calyces. To study whether these claims are valid, it is necessary to produce an extract with a high anthocyanin content and to have available a method to identify and quantify the individual compounds in the product. A method of extraction and purification has been developed based on a polyamide column chromatographic purification step. Using this method, anthocyanin concentrates were produced containing from 57 to 64% of delphinidin-3- sambubioside plus cyanidin-3-sambubioside. A rapid, efficient and validated HPLC analytical method was developed and used for the analysis of the anthocyanin concentrate.

Carbonyl reduction of warfarin: Identification and characterization of human warfarin reductases.

Warfarin is a widely used anticoagulant and, unfortunately, is a drug that is commonly implicated in serious adverse events including fatalities. Although several factors, including the metabolism of warfarin via CYP450, have been reported to affect the safety and efficacy of warfarin therapy, the wide variance in the warfarin dosage in patients has not been completely clarified. In addition to the oxidative metabolism of warfarin mediated by CYP450, reductive metabolism is involved in warfarin biotransformation. However, the reductive metabolism of warfarin has been largely unexplored and deserves further investigation. We studied warfarin reduction by human liver fractions and found a 9-fold higher velocity of warfarin reduction in the cytosol than in microsomes (Vmax=77.2 vs. 8.7pmol/mgprotein/min, respectively). Furthermore, of nine recombinant cytosolic carbonyl reducing enzymes tested for their ability to reduce warfarin, AKR1C3 and CBR1 were identified as warfarin reductases and their kinetic parameters were determined. The internal clearance of warfarin was 3 orders of magnitude higher with AKR1C3 than with CBR1 (CLint=65.922 vs. 0.070µl/mgprotein/min, respectively). This is the first time that warfarin reducing enzymes in human liver subcellular fraction have been identified. Moreover, we have described the chiral aspects of warfarin reduction using an HPLC method that enabled the detection of individual warfarin alcohol stereoisomers. Cytosol and AKR1C3 exhibit the stereoselective metabolism of (R)-warfarin to preferentially form (SR)-warfarin alcohol as the primary in vivo metabolite of warfarin. On the other hand, microsomes and CBR1 preferentially reduce (S)-warfarin to form (RS)-warfarin alcohol and (SS)-warfarin alcohol, respectively.