Spectrophotometric Determination of Rifampicin through Chelate Formation and Charge Transfer Complexation in Pharmaceutical Preparation and Biological Fluids

State of the Art on Developments of (Bio)Sensors and Analytical Methods for Rifamycin Antibiotics Determination

This review summarizes the literature data reported from 2000 up to the present on the development of various electrochemical (voltammetric, amperometric, potentiometric and photoelectrochemical), optical (UV-Vis and IR) and luminescence (chemiluminescence and fluorescence) methods and the corresponding sensors for rifamycin antibiotics analysis. The discussion is focused mainly on the foremost compound of this class of macrocyclic drugs, namely rifampicin (RIF), which is a first-line antituberculosis agent derived from rifampicin SV (RSV). RIF and RSV also have excellent therapeutic action in the treatment of other bacterial infectious diseases. Due to the side-effects (e.g., prevalence of drug-resistant bacteria, hepatotoxicity) of long-term RIF intake, drug monitoring in patients is of real importance in establishing the optimum RIF dose, and therefore, reliable, rapid and simple methods of analysis are required. Based on the studies published on this topic in the last two decades, the sensing principles, some examples of sensors preparation procedures, as well as the performance characteristics (linear range, limits of detection and quantification) of analytical methods for RIF determination, are compared and correlated, critically emphasizing their benefits and limitations. Examples of spectrometric and electrochemical investigations of RIF interaction with biologically important molecules are also presented.

Preparation, spectroscopic, characterizations and biological studies of new charge transfer complexes formed between fluconazole drug with various acceptors

Charge transfer complexes developed during the interaction of Fluconazole drug (FLU) as an electron donor with different types of electron acceptors, including σ-type as iodine (I₂), and π-types as 2,3-dinitrosalsylic acid (HDNS), Tetracyanoethylene (TCNE) and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The formed complexes were characterized using various techniques as UV-Vis spectra, Thermal analyses, spectrophotometric measurements, ¹H NMR and FTIR Spectroscopy. It was found that the stoichiometry of all developed complexes was a 1:1 M ratio between fluconazole and acceptors (I₂, HDNS, TCNE and DDQ). The characteristic physical parameters data such as ionization potential (I_D), The oscillator strength (ƒ), formation constant (K_CT), transition dipole moment (μ), free energy (ΔG), and energy of interaction (E_CT) of the formed CT-complexes have also been reported. Eventually, the synthesized complexes were screened for their microbial and antioxidant activities.

UV-Vis, FTIR, 1H, 13C NMR spectra and thermal studies of charge transfer complexes formed in the reaction of Gliclazide with π- and σ-electron acceptors

Charge transfer interactions (CT) between a gliclazide (GLC) donor and a picric acid (PA) π acceptor or iodine σ acceptor, were studied in a chloroform solution and in the solid state. UV-vis spectroscopy elucidated the formation of the complexes, and allowed determination of the stoichiometry, stability constants (K), and thermodynamic quantities (ΔG°, ΔH°, and ΔS°), and spectroscopic properties such as the molar extinction coefficient (ε_CT), oscillator strength (f), transition dipole moment (μ_EN), and ionization potential (I_p). Beer's law was obeyed over the 2-8 and 4-12 μg mL^-1 concentration ranges for GLC with PA (method A) and I₂ (method B), respectively, with correlation coefficients of 0.9986 and 0.9989. The limits of detection (LOD) and limits of quantification (LOQ) have also been reported. The 1:1 stoichiometric CT complexes were synthesized and characterized by FTIR, ¹H, and ¹³C NMR spectroscopy. The results indicated a favorable proton migration from PA to the donor molecule, and an interaction between the NH of GLC and iodine. Thermogravimetric analysis techniques (TGA/DTA) and differential scanning calorimetry (DSC) were used to determine the thermal stability of the synthesized CT complex. The kinetic parameters (ΔG*, ΔH*, and ΔS*) were calculated from thermal decomposition data using the Coats-Redfern method.

Feeling Nature's PAINS: Natural Products, Natural Product Drugs, and Pan Assay Interference Compounds (PAINS)

We have previously reported on classes of compounds that can interfere with bioassays via a number of different mechanisms and termed such compounds Pan Assay INterference compoundS, or PAINS. These compounds were defined on the basis of high-throughput data derived from vendor-supplied synthetics. The question therefore arises whether the concept of PAINS is relevant to compounds of natural origin. Here, it is shown that this is indeed the case, but that the context of the biological readout is an important factor that must be brought into consideration.

A spectrophotometric and thermodynamic study of the charge-transfer complexes of N-aryl-N'-isopropyloxycarbonylsulfamides with DDQ and TCNE

Molecular charge-transfer complexes of three N-aryl-N'-isopropyloxycarbonylsulfamides derivatives with π-acceptors tetracyanoethylene (TCNE), and 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ), were studied by using zero and second order derivative UV spectrophotometry in different solvents at four different temperatures within the range of 20-35 °C. The stoichiometries of the complexes were found to be 1:1 ratio between donors and acceptors using Job's method. The data were analyzed in terms of their stability constant (K), molar extinction coefficient (εCT), thermodynamic standard reaction quantities (ΔG°, ΔH°, ΔS°), oscillator strength (f), transition dipole moment (μEN) and ionization potential (ID). The results show that the stability constant (K) for the complexes was found to be dependant upon the nature of electron acceptor, electron donor, and polarity of used solvents.

Synthesis, spectroscopic investigations, antimicrobial and DNA binding studies of a new charge transfer complex of o-phenylenediamine with 3,5-dinitrosalicylic acid

A charge transfer complex of o-phenylenediamine (OPD) as donor with 3,5-dinitrosalicylic acid (DNSH) as acceptor, was synthesized and characterized by FTIR, (1)H NMR, (13)C NMR, mass spectroscopy, elemental analysis and X-ray crystallography. The structural investigations exhibit that the cation and anion are joined together by strong N(+)H⋯O(-) type hydrogen bonds and stoichiometry of CT complex was found to be 1:1. The CT (charge transfer) complex shows remarkable interaction with Calf thymus DNA, and the CT complex was also screened for its microbial activity such as antimicrobial and antifungal activities. A molecular frame work through H-bonding interactions via n→π(*) transitions between neighboring moieties is found which is responsible for high melting point of resulting CT complex. This has been attributed to the formation of 1:1 CT complex.

Biowaiver monographs for immediate release solid oral dosage forms: rifampicin

Literature data relevant to the decision to allow a waiver of in vivo bioequivalence (BE) testing for the approval of new multisource and reformulated immediate release (IR) solid oral dosage forms containing rifampicin as the only Active Pharmaceutical Ingredient (API) are reviewed. Rifampicin's solubility and permeability, its therapeutic use and index, pharmacokinetics, excipient interactions and reported BE/bioavailability (BA) problems were taken into consideration. Solubility and absolute BA data indicate that rifampicin is a BCS Class II drug. Of special concern for biowaiving is that many reports of failure of IR solid oral dosage forms of rifampicin to meet BE have been published and the reasons for these failures are yet insufficiently understood. Moreover, no reports were identified in which in vitro dissolution was shown to be predictive of nonequivalence among products. Therefore, a biowaiver based approval of rifampicin containing IR solid oral dosage forms cannot be recommended for either new multisource drug products or for major scale-up and postapproval changes (variations) to existing drug products.

Multicomponent kinetic spectrophotometric determination of pefloxacin and norfloxacin in pharmaceutical preparations and human plasma samples with the aid of chemometrics

A spectrophotometric method for the simultaneous determination of the important pharmaceuticals, pefloxacin and its structurally similar metabolite, norfloxacin, is described for the first time. The analysis is based on the monitoring of a kinetic spectrophotometric reaction of the two analytes with potassium permanganate as the oxidant. The measurement of the reaction process followed the absorbance decrease of potassium permanganate at 526 nm, and the accompanying increase of the product, potassium manganate, at 608 nm. It was essential to use multivariate calibrations to overcome severe spectral overlaps and similarities in reaction kinetics. Calibration curves for the individual analytes showed linear relationships over the concentration ranges of 1.0-11.5 mg L(-1) at 526 and 608 nm for pefloxacin, and 0.15-1.8 mg L(-1) at 526 and 608 nm for norfloxacin. Various multivariate calibration models were applied, at the two analytical wavelengths, for the simultaneous prediction of the two analytes including classical least squares (CLS), principal component regression (PCR), partial least squares (PLS), radial basis function-artificial neural network (RBF-ANN) and principal component-radial basis function-artificial neural network (PC-RBF-ANN). PLS and PC-RBF-ANN calibrations with the data collected at 526 nm, were the preferred methods--%RPE(T) approximately 5, and LODs for pefloxacin and norfloxacin of 0.36 and 0.06 mg L(-1), respectively. Then, the proposed method was applied successfully for the simultaneous determination of pefloxacin and norfloxacin present in pharmaceutical and human plasma samples. The results compared well with those from the alternative analysis by HPLC.