Influence of ortho group in rhodamine B hydrazide based Schiff base for selective recognition of Cu2+ and Fe3+ ions: A mechanistic approach by DFT and colorimetric studies

Herein we have implemented a computational approach in designing sensor molecules for the selective recognition of Cu²⁺ and Fe³⁺ ions. Seven rhodamine B hydrazide-based Schiff base derivatives were designed and analysed their chemosensing properties against Cu²⁺ and Fe³⁺ ions in ethanol solution theoretically. The theoretical calculations revealed that the selective recognition of Cu²⁺ and Fe³⁺ ions takes place via spirolactam ring-opening and there is a pivotal role of ortho substituents and N-heteroatoms. The two best chemosensors were synthesised and used for the detection of Cu²⁺ and Fe³⁺ ions by colorimetric methods.

Time progression and regional expression of brain oxidative stress induced by obstructive jaundice in rats

BACKGROUND

Obstructive jaundice induces oxidative changes in the brain parenchyma and plays significant role in clinical manifestations of hepatic encephalopathy. We aim to study the progression of the brain oxidative status over time and the differences of its pattern over the hemispheres, the brainstem and the cerebellum. We use an experimental model in rats and measuring the oxidative stress (OS) specific biomarkers protein malondialdehyde (PrMDA) and protein carbonyls (PrC = O).

RESULTS

Hyperbilirubinemia has been confirmed in all study groups as the result of common bile duct obstruction. We confirmed increase in both PrMDA and PrC = O biomarkers levels with different type of changes over time. We also confirmed that the oxidative process develops differently in each of the brain areas in study.

CONCLUSIONS

The present study confirms the progressive increase in OS in all brain areas studied using markers indicative of cumulative protein modification.

Protein carbonyl determination by a rhodamine B hydrazide-based fluorometric assay

A new fluorometric assay is presented for the ultrasensitive quantification of total protein carbonyls, and is based on their specific reaction with rhodamine B hydrazide (RBH), and the production of a protein carbonyl-RBH hydrazone the fluorescence of which (at ex/em 560/585 nm) is greatly enhanced by guanidine-HCl. Compared to the fluorescein-5-thiosemicarbazide (FTC)-based fluorometric assay, the RBH assay uses a 24-fold shorter reaction incubation time (1 h) and at least 1000-fold lower protein quantity (2.5 µg), and produces very reliable data that were verified by extensive standardization experiments. The protein carbonyl group detection sensitivity limit of the RBH assay, based on its standard curve, can be as low as 0.4 pmol, and even lower. Counting the very low protein limit of the RBH assay, its cumulative and functional sensitivity is 8500- and 800-fold higher than the corresponding ones for the FTC assay. Neither heme proteins hemoglobin and cytochrome c nor DNA interfere with the RBH assay.

Determination of malondialdehyde in biological fluids by high-performance liquid chromatography using rhodamine B hydrazide as the derivatization reagent

Malondialdehyde (MDA) is a biomarker for lipid peroxidation, and studies of sensitive and selective analytical methods for it are very important for pathological research. The aim of this work was to develop and validate a novel HPLC method for the quantification of MDA in biological fluids using rhodamine B hydrazide (RBH) as the derivatization reagent. After pretreatment and derivatization in acid medium at 50 °C for 40 min, the RBH-derivatized MDA was separated on a Kromasil C18 column at 25 °C and detected by a fluorescence detector at excitation wavelength of 560 nm and emission wavelength of 580 nm. The results showed linearity in the range of 0.8-1500.0 nM with a detection limit of 0.25 nM (S/N = 3). The recovery of MDA from plasma and urine was 91.50 to 99.20%, with a relative standard deviation range of 1.45 to 3.26%. In comparison to other methods reported for the determination of MDA, the proposed method showed superiority in simplicity, more sensitivity, shorter derivatization time, and less interference. The developed method was applied to quantification of MDA in human biological fluids collected from five volunteers with a concentration range of 24.62-245.00 nM.