Polyclonal Murine and Rabbit Antibodies for the Bile Acid Isolithocholic Acid

Re-assessment of monoclonal antibodies against diclofenac for their application in the analysis of environmental waters

The non-steroidal anti-inflammatory drug (NSAID) diclofenac (DCF) is an important environmental contaminant occurring in surface waters all over the world, because, after excretion, it is not adequately removed from wastewater in sewage treatment plants. To be able to monitor this pollutant, highly efficient analytical methods are needed, including immunoassays. In a medical research project, monoclonal antibodies against diclofenac and its metabolites had been produced. Based on this monoclonal anti-DCF antibody, a new indirect competitive enzyme-linked immunosorbent assay (ELISA) was developed and applied for environmental samples. The introduction of a spacer between diclofenac and the carrier protein in the coating conjugate led to higher sensitivity. With a test midpoint of 3 μg L-1 and a measurement range of 1-30 μg L-1, the system is not sensitive enough for direct analysis of surface water. However, this assay is quite robust against matrix influences and can be used for wastewater. Without adjustment of the calibration, organic solvents up to 5%, natural organic matter (NOM) up to 10 mg L-1, humic acids up to 2.5 mg L-1, and salt concentrations up to 6 g L-1 NaCl and 75 mg L-1 CaCl2 are tolerated. The antibody is also stable in a pH range from 3 to 12. Cross-reactivity (CR) of 1% or less was determined for the metabolites 4'-hydroxydiclofenac (4'-OH-DCF), 5-hydroxydiclofenac (5-OH-DCF), DCF lactam, and other NSAIDs. Relevant cross-reactivity occurred only with an amide derivative of DCF, 6-aminohexanoic acid (DCF-Ahx), aceclofenac (ACF) and DCF methyl ester (DCF-Me) with 150%, 61% and 44%, respectively. These substances, however, have not been found in samples. Only DCF-acyl glucuronide with a cross-reactivity of 57% is of some relevance. For the first time, photodegradation products were tested for cross-reactivity. With the ELISA based on this antibody, water samples were analysed. In sewage treatment plant effluents, concentrations in the range of 1.9-5.2 μg L-1 were determined directly, with recoveries compared to HPLC-MS/MS averaging 136%. Concentrations in lakes ranged from 3 to 4.4 ng L-1 and were, after pre-concentration, determined with an average recovery of 100%.

Total glycosides contribute to the anti-diarrheal effects of Qiwei Baizhu Powder via regulating gut microbiota and bile acids

Qiwei Baizhu Powder (QWBZP) is a traditional Chinese medicine formula for treating diarrhea induced by various causes. It elicits an anti-diarrheal effect by regulating the gut microbiota (diversity, structure, and abundance). However, the contribution of different components in the QWBZP decoction to this effect remains unclear. In this study, we used the QWBZP decoction as a reference standard to investigate the effects of total glycosides (TGs) extracted from QWBZP decoction on the gut microbiota and bile acid metabolism in mice with antibiotic-associated diarrhea (AAD). The results of 16S rRNA gene sequencing and liquid chromatography-mass spectrometry (LC-MS) analysis showed that the effect of total glycosides of Qiwei Baizhu Powder (QWBZP-TG) on specific intestinal bacteria and bile acids was similar to that of the QWBZP decoction, but the intensity of this effect was more significant in the case of QWBZP-TG. The QWBZP decoction and QWBZP-TG promoted the proliferation of Lactobacillus and inhibited the growth of Proteus, Clostridium, Eubacterium, Facklamia, and Escherichia in AAD mice. They also increased the levels of deoxycholic acid and beta-muricholic acid and decreased those of taurocholate acid, tauro-alpha-muricholic acid, and tauro-beta-muricholic acid in AAD mice. Lactobacillus was the key bacterial genus responding to QWBZP-TG. Thus, this study provides novel insights into the bioactive components of QWBZP and their contribution to its effects.

Enzyme-linked immunosorbent assay (ELISA) for the anthropogenic marker isolithocholic acid in water

Bile acids are promising chemical markers to assess the pollution of water samples with fecal material. This study describes the optimization and validation of a direct competitive enzyme-linked immunosorbent assay for the bile acid isolithocholic acid (ILA). The quantification range of the optimized assay was between 0.09 and 15 μg/L. The assay was applied to environmental water samples. Most studies until now were focused on bile acid fractions in the particulate phase of water samples. In order to avoid tedious sample preparation, we undertook to evaluate the dynamics and significance of ILA levels in the aqueous phase. Very low concentrations in tap and surface water samples made a pre-concentration step necessary for this matrix as well as for wastewater treatment plant (WWTP) effluent. Mean recoveries for spiked water samples were between 97% and 109% for tap water and WWTP influent samples and between 102% and 136% for WWTP effluent samples. 90th percentiles of intra-plate and inter-plate coefficients of variation were below 10% for influents and below 20% for effluents and surface water. ILA concentrations were quantified in the range of 33-72 μg/L in influent, 21-49 ng/L in effluent and 18-48 ng/L in surface water samples. During wastewater treatment the ILA levels were reduced by more than 99%. ILA concentrations of influents determined by ELISA and LC-MS/MS were in good agreement. However, findings in LC-ELISA experiments suggest that the true ILA levels in concentrated samples are lower due to interfering effects of matrix compounds and/or cross-reactants. Yet, the ELISA will be a valuable tool for the performance check and comparison of WWTPs and the localization of fecal matter input into surface waters.