Current Analytical Chemistry - Volume 16, Issue 2, 2020

Background: A simple, rapid and efficient method for the determination of curcumin and other polyphenols in turmeric and curry samples was here developed. The method relied on sample extraction with methanol and extract analysis by liquid chromatography with diode array detection (HPLC-DAD). Methods: The separation of components was carried out in reversed-phase mode using an elution gradient based on 0.1% (v/v) formic acid aqueous solution and acetonitrile as the components of the mobile phase. Chromatograms were recorded at 420 nm for specific monitoring of curcumin and related compounds. Results: Extraction and separation conditions were optimized by experimental design and multicriteria response functions. Figures of merit were established under the selected experimental conditions. In general, repeatability of peak areas were better than 0.4%, detection limits were below 0.006 mg L-1 and quantitative recoveries expressed as a percentage were about 100 ± 2. The method was applied to quantify curcuminoids in commercial samples. It was found that apart from curcumin, demethoxycurcumin and bisdemethoxycurcumin, other related molecules also occurred in the samples. In this regard, a tentative elucidation of possible unknown curcuminoids was attempted by liquid chromatography coupled to mass spectrometry. Conclusion: Differences in the compositional profiles among samples were encountered to be relevant, so that the resulting HPLC-DAD data was exploited for chemometric characterization of turmeric and curry samples. Samples were successfully discriminated according to matrix types, species varieties and origins.

Background: Medicinal plants consist a rich source of natural pharmacologically active compounds. The aim of the current work, was the study and optimization of the extraction conditions of phenolic constituents from important medicinal and aromatic plants, id. Sideritis raeseri, Sideritis scardica and Origanum vulgare, implementing microwave assisted extraction technique. Methods: Optimization was based on various parameters affecting extraction procedure, such as the duration of microwave radiation, the ratio of plant material mass to the solvent, the type and the concentration of the solvent. Results: The results revealed that 10 min of microwave radiation provided the maximum extraction yield of the phenolic constituents. The ratio of the plant material mass and the solvent had minor effect to the extraction efficiency. Conclusion: The examined solvents provided an extraction yield of phenolic constituents following the order: EtOH < MeOH < H2O < MeOH:H2O (80:20, v/v) < EtOH:H2O (60:40, v/v), in the case of Sideritis raeseri and Sideritis scardica and the order: H2O < MeOH:H2O (80:20, v/v) < EtOH:H2O (60:40, v/v) < MeOH < EtOH in the case of Origanum vulgare.

Background: Reactive oxygen species are formed through the electron transfer reactions in the mitochondria and chloroplasts and rapidly converted to H2O2.Therefore, H2O2 as a more stable ROS can be considered as an indicator of cellular stress and it can be used in a steady state to monitor intracellular stress level. In this regard, the increasing use of various nanoparticles, most of which are associated with biological systems, are essential to be studied for their possible adverse effects. We measured the concentration of hydrogen peroxide in samples collected before and after the treatment with silver nanoparticles by a novel method and optimized this method for the living tissue. Methods: In this study, we evaluated the endogenous H2O2 production from Pyricularia oryzae tissue under normal and stress conditions (such as after treatment with nanoparticles) by spectrophotometric assay. The method used is based on instant reaction of hydrogen peroxide with vanadium pentoxide in sulfuric acid solution, forming a peroxovanadate complex that has a maximum absorption at 454 nm. This method was also compared with other methods. Results: The results of this method compared with other methods in the same tissue showed that the method is simple, inexpensive and more efficient, and the complex is stable for several hours and can be used for a variety of H2O2 concentrations. Also, the detection range of the mentioned method equals with high-sensitivity methods such as available commercial kits. Furthermore, this method can also measure higher values of H2O2. Conclusion: The optimized methods for measuring the H2O2 concentration with vanadium pentoxide in sulfuric acid solution by the colorimetric method are simple, efficient, rapid, accurate, cost-effective and do not have problems of other methods. The measurements using this method in Pyricularia oryzae under oxidative stress showed that the created oxidative stress caused by the use of silver nanoparticles increased H2O2 in fungal tissue. H2O2 is the SOD reaction product that is later decomposed by CAT. This method is able to measure H2O2 in different ranges and under normal and stress conditions which are indicative of antioxidant defense. Therefore, we recommend it to the researchers in similar conditions.

Background: Molecularly imprinted polymers (MIPs) are utilized in the separation of a pure compound from complex matrices. A stable template-monomer complex generates MIPs with the highest affinity and selectivity for the template. In this investigation, degradation of Poly(ethylene terephthalate) PET afforded the (E)-4-(2-cyano-3-(dimethylamino) acryloyl) benzoic acid (4) (TAM) which used TAM as template which interacts with Methacrylic Acid (MAA) monomer, in the presence of CH3CN as progen. The TAM-MMA complex interactions are dependent on stable hydrogen bonding interaction between the carboxylic acid group of TAM and the hydroxyl group of MMA with minimal interference of porogen CH3CN. The DFT/B3LYP/6-31+G model chemistry was used to optimize their structures and frequency calculations. The binding energies between TAM with different monomers showed the most stable molar ratio of 1:4 which was confirmed through experimental analysis. Methods: The present work describes the synthesis of (E)-4-(2-cyano-3-(dimethylamino) acryloyl) benzoic acid (4) (TAM) from PET waste and formation of molecularly imprinted polymer from TAM with the methacrylic acid monomer. The optimization of molecular imprinted was stimulated via DFT/B3LYP/6-31G (d). The imprinted polymer film was characterized via thermal analysis, pore size, FT-IR and scanning electron microscopy. Results: The most stable molecularly imprinted polymers (MIPs) showed binding energy of TAM(MMA4)=-2063.456 KJ/mol with a small value of mesopores (10-100 Å). Also, the sorption capability of TAM-MIPs showed 6.57 mg/g using STP-MIP-9VC. Moreover, the average pore size ranged between 0.2-1 nm with the BET surface about 300 m2/g. Conclusion: The proposed TAM exhibited a high degree of selectivity for MMA in comparison with other different monomers through hydrogen bond interaction, which was thermally stable, good reproducibility and excellent regeneration capacity and elucidated in the computational study and analytical analysis.

Background: Nanocomposites are of great interest due to their competency to show multifunctional properties. They have been recently given much attention due to their credibility to offer the synergistic feature of organic material with those of inorganic constituents. Different types of nanocomposites have been prepared to date and are being used for different applications. The delivery of drugs in the human body at a particular site was one of the major problems in the medicinal field. The nanocomposite formulations can be used to provide controlled release and they can be combined with ligands for targeted drug delivery. Applications of the nanocomposites as ion exchangers are also increasing at a faster rate. Due to this, they help in the softening of the water. They can also be easily recharged by washing them with a solution containing a high concentration of sodium ions. In the present paper, we have worked on the synthesis and applications of the polysorbate/ironmolybdophosphate (PS/FMP) nanocomposite. Methods: Polysorbate/ironmolybdophosphate (PS/FMPS) was synthesized by co-precipitation method in the presence of polysorbate. The material was well characterized using X-ray diffraction (XRD) analysis, Fourier transform infrared spectroscopy, (FTIR) scanning transmission microscopy (SEM), and transmission electron microscopy (TEM). Physicochemical properties of material were studied in detail. Drug delivery behavior of polysorbate/ironmolybdophosphate was investigated by using methylcobalamin as a test drug. Results: The polysorbate/ironmolybdophosphate nanocomposite show enhanced Na+ ion exchange capacity of 2.1 meq/g. It has been revealed that PS/FMP nanocomposite was thermally stable as it retained the ion exchange capacity of 40.4 % at 400°C. An optimum concentration of sodium nitrate (eluent) was found to be 1.0 M for the complete removal of H+ ions from the PS/FMP column. The optimum volume of sodium nitrate (eluent) was found to be 230 mL. The FTIR spectra showed the changes in intensities of characteristic peaks in PS/FMP and in drug loaded on PS/FMP nanocomposite. The characteristic peak at 1043-1061 cm-1 was observed for ionic phosphate stretching, 560-567 cm-1 for iron group and 959 cm-1 due to molybdate present in the material. The additional peak at 3390 cm-1 and 1711 cm-1 were due to -OH and C=O stretching due to the presence of these groups in the structure of polysorbate. The peak present at 430 cm-1 might be due to the presence of Co-O stretching of methylcobalamin. The XRD results confirmed the semicrystalline structure of FMP and PS/FMP. Scanning electron micrographs results revealed the beaded surface of FMP changes to fibrous surface in case of PS/FMP nanocomposite. The TEM images indicate the appearance of smooth surfactant layer on the surface of FMP. The size of the nanocomposite is between 10- 70 nm. The drug loading efficiency and encapsulation efficiency were found to be 35.2%. and 60.4%, respectively. The cumulative drug release of methylcobalamin was studied for the PS/FMP nanocomposite. The order of drug release was found to be pH 9.4 (54.6%) > pH 7.4 (46.4%) > saline (pH 5.7) (36.2%) > pH 2.2 (33.9%). The release at pH 9.4 was higher. As the pH of medium changes from acidic to basic i.e. 2.2 - 9.4, there is an appreciable increase in drug release from the PS/FMP nanocomposite due to the presence of more OH- ions resulting in neutralization of cationic nanocomposite and thus increasing the rate of drug release by ion exchange process and matrix deterioration. Conclusion: The novel nanocomposite PS/FMP has been synthesized by a simple co-precipitation method. The increase in Na+ ion exchange capacity for nanocomposite is due to the binding of organic part (Polysorbate) with inorganic ironmolybdophosphate. The physiochemical properties of PS/FMP were found to be superior. Fourier transform infrared spectra of PS/FMP and drug loaded PS/FMP confirmed the formation of materials. The SEM results indicated the surface of synthesized FMP is bead-like appearance whereas the beaded surface of FMP changes to fibrous surface on the addition of polysorbate thus indicated the fabrication of nanocomposite. The cumulative drug release of methylcobalamin was studied and the order of drug release was found to be pH 9.4 > pH 7.4 > saline (pH 5.7) > pH 2.2. Thus PS/FMP is a promising multifunctional nanocomposite.

Background: A stability indicating high-performance thin layer chromatography (HPTLC) method was developed for the evaluation of fisetin (FIS) in active pharmaceutical ingredient (API) and marketed capsule formulation in accordance with the ICH guidelines. Methods: The mobile phase combination toluene: ethyl acetate: formic acid: methanol (3: 5.5: 1: 0.5 v/v/v/v) was optimized with the aid of AQbD approach. The absorbance mode at 254 nm was chosen for densitometric analysis as it gives a compact spot of FIS at Rf value of 0.74. Results: The R2 value obtained from the linear regression equation of calibration plots made by taking the spot in the concentration range of 100-1400 ng/spot was found to be 0.9993. The observed LOD and LOQ value was found to be 29.8 ng/spot and 98.5 ng/spot, respectively. The exposure of FIS to various stress conditions revealed the fact that the drug is stable in photochemical and dry heat stress conditions without any degradation. The drug-exposed to acidic, alkaline and oxidative stress was found to be degraded into different degradation products with the highest degradation was found in alkaline stress. All degradation products were observed to be fairly separated from well-resolved parent peak of FIS. Conclusion: The developed HPTLC method have shown well-resolved peaks and also shown good recovery in the compound FIS as well as FIS formulation.

Background: The available data concerning aqueous dissociation constant of mupirocin (sparingly soluble drug) are scarce. In this study, chromatographic, surfactant based potentiometric concept and spectrophotometric method were used for determination of the aqueous pKa value of mupirocin. Methods: Different approaches were used for estimation of the aqueous pKa value from the apparent pKa values obtained at four ACN concentrations, ranging from 22% to 30%. The potentiometric determination of the pKa value of mupirocin was performed using different concentration of Tween 80 as a surfactant. Results: The aqueous pKa value of mupirocin, determined for the first time by reverse-phase liquid chromatography method, was found to be 4.76. The obtained value was confirmed by potentiometric method (4.85). It was found that Tween 80 increases the pKa values. The linear relationship between the apparent pKa values and the surfactant concentrations was used as an approach for estimation of the aqueous pKa value. Both methods gave similar values for aqueous pKa which correspond with the theoretically obtained pKa value (4.88) using Pallas computer program. It was found that mupirocin gives pH-indipendent spectra, thus spectrophotometric method is not applicable for determination of pKa of this compound. Conclusion: This comprehensive approach used for the pKa determination enable us to obtained reliable results for the aqueous pKa value of mupirocin. The linear relationship between the pKa values and the nonionic surfactant concentrations could be used as a reliable and simple approach for determination of aqueous pKa value of sparingly soluble drugs.

Background: Volatile compounds in fish sauce may vary due to the species of fish, ingredients, processing period, temperature, and even the preference of people in each area. It is necessary to study a method of distinguishing the origins of fish sauce. The aims of this paper are to introduce a method to classification of fish sauce origin by means of electronic nose fingerprint and gas chromatography- mass spectrometry of volatile compounds and the two artificial neural networks are used to predict the origins of fish sauce. Methods: Headspace sampling-solid phase microextraction combined with gas chromatography-mass spectrometric analysis and electronic nose were used to analysze volatile compounds in different origins of fish sauce, and these dates predicted the origins of fish sauce by artificial neural networks. Results: 94 volatile compounds were identified by Automatic mass spectral deconvolution and identification system, out of which 44 are from Guangdong, 53 from our laboratory, 51 from Vietnam, 47 and 45 from Thailand. Then electronic nose was applied to identify the origin of fish sauce, and the data were analyzed using principal component analysis and load analysis. The fish sauce from different origin can be classified well on the PCA plot. Lastly, two artificial neural networks are used to predict the origins of fish sauce, and the accuracy rates of radial basis and gradient descent both are 93.33%. Conclusion: That illustrates that we can provide a quick method to distinguish fish sauce products of different origins. These results indicated that the combinations of multiple analysis and identification methods could make up the limitations of a single method, enhance the accuracy of identification, and provide useful information for product development.

Background: The total antioxidant capacity of yam food grown in southern African regions was investigated by a polyglycine-glassy carbon modified electrode. The modified electrode was fabricated using glycine solution on glassy carbon electrode by electrodeposition method. The proposed modified electrode is found to be nearly 3.15-fold more sensitive than the bare electrode. For the measurement of the total antioxidants of yam, differential pulse stripping voltammetry (DPSV) was employed with standard quercetin compound. Methods: The total antioxidant capacity of yam was deduced by DPSV and cyclic voltammetry (CV) methods. The basic parameters for the stripping technique such as pH, accumulation time and accumulation potential were optimized as 20 s, 200 mV and a pH of 3 Britton-Robinson (B-R) buffer solutions in 0.5 mg quercetin/L, respectively. Results: In the optimization condition, the linear working range was determined between 5.0 μg/L and 80.0 μg/L for the quercetin. The detection (LOD) and quantification (LOQ) limits of quercetin were found to be 0.39 μg/L and 1.39 μg/L on the modified electrode by DPSV, respectively. The procedure was also applied to natural yam samples and total antioxidant capacity of 0.1 kg of yam was determined as 96.15 ± 0.85 μg/L of equivalent quercetin at 95% confidence level with the relative standard deviations of 0.88%. Conclusion: Sensitive and selective voltammetric method was developed for the determination of total antioxidant capacity in yam. Moreover, the modified polyglycine-glassy carbon electrode was constructed more selectively for quercetin. As a result, a simple, sensitive and rapid new voltammetric method for the determination of antioxidants has been developed using the modified electrode.

Objective: In order to test real direct applicability for analytical purposes, a small and simple direct methanol (or ethanol) catalytic, enzymatic or non-enzymatic fuel cell (DMFC) was used for the analysis of ethanol-based pharmaceutical tinctures; a detailed experimental study was conducted on five different pharmaceutical tinctures available at drugstores. Results: The results obtained using both enzymatic and non-enzymatic devices were compared with those obtained by analyzing the same pharmaceutical samples with a conventional catalase biosensor. Finally, the results were compared with the nominal values provided by manufacturing firms. Conclusion: The correlations between the different experimental and nominal values considered were good in general or satisfactory and the applied statistical tests (f-test and t-test) were also very comforting. At the end of the study, the use of enzymatic DMFC proved to be better than non- enzymatic DMFC devices, because it requires shorter analysis times.