Current Analytical Chemistry - Volume 20, Issue 2, 2024

Metal-organic frameworks (MOFs), a crystalline material, are a new type of inorganicorganic hybrid material. MOFs are of great interest to researchers in chemistry and material science due to their various chemical and physical properties, and features include their remarkable surface area, high porosity, flexibility, structural variety, flexibility, extreme porosity, a large surface area, augmented adsorption/desorption kinetics, biocompatibility and functional tunability. MOFs are multi-dimensional crystals and have extended net-like frameworks from molecular building units such as inorganic metal nodes and organic linkers. The structurally diverse MOFs have found applications in chemical sensing and several other fields, such as energy applications, biomedicine, and catalysis. Numerous researchers from other fields have been drawn to this topic by the intrinsic potential to absorb gas molecules, which has led to the applications of gas storage and heterogeneous catalysis. Because of their low framework density, open metal sites for interaction, adjustable pore size, fast response with high sensitivity and selectivity, and real-time monitoring, luminescent metalorganic frameworks, or LMOFs, have piqued the interest of a large scientific community as a promising candidate for sensor applications. A number of characteristics, including non-toxicity, biodegradability, and reasonably priced, varied functionality, are important factors in the use of MOFs in chemo- and biosensing. MOFs can be very promising candidates as selective and sensitive chemosensors for the detection of cations, anions, small molecules, gases and explosives. In this manuscript, we address recent research advances in the use of metal-organic-framework-based luminescent sensors for detecting some small molecules and various metal ions in aqueous biological and environmental samples. A wide range of materials may be reached in the emerging field of synthetic and material chemistry, thanks to the capacity to change the pore size and chemically functionalize its nature without changing its architecture.

An immediate and precise diagnosis is required due to the COVID-19 outbreak. Labelfree electrochemical biosensors show promise as potentially valuable instruments for detecting COVID-19. These biosensors are distinguished by their lack of complexity, high speed, sensitivity, and relatively low cost. The precise COVID-19 biomarkers may be recognized without labeling or amplification by detecting the electrical signal created by direct contact between the target analyte and the identification element positioned on the electrode surface. This can be done by placing the electrode in contact with the target analyte, which will amplify the signal. It has been shown that using gold screen printed electrodes, also known as Au SPE, is beneficial when used as an electrode material in label-free electrochemical biosensors. This review study examines and contrasts the performance of several label-free electrochemical biosensors that use Au SPE to detect COVID-19. The merits and limitations of each biosensor will also be discussed. These biosensors use recognition components like DNA, RNA, antibody, aptamer, and MIP and depend on various indicators, such as viral RNA, viral protein, and host antibody. In addition, an analysis of the difficulties and possibilities that may present within this burgeoning subject is carried out. This includes the enhancement of sensor selectivity and stability, optimizing sensor manufacture and design, integrating the sensor with portable readout equipment, and validating the sensor's effectiveness via the use of genuine clinical samples. It can be reasoned out that label-free electrochemical biosensors that make use of gold screen-printed electrodes (Au SPE) have a significant amount of potential for the detection of COVID-19. However, further study is required to address various difficulties, improve their dependability, and broaden the range of applications for these technologies.

Background: Oxidative damage to biological molecules is mainly caused by free radicals produced in the body. Natural antioxidants can prevent the resulting oxidative stress. For this purpose, particularly grapes and grape products, which contain vitamins and polyphenolic substances with high antioxidant activity, are used.

Methods: In the present study, the content of vitamins C and E, beta-carotene, and some flavonoids (+)-catechin, quercetin, and trans-resveratrol) in the composition of 19 brands of red wines that are produced in Armenia, was determined by HPLC. Vitamins C, E, beta-carotene, as well as flavonoids manufactured by Sigma-Aldrich were used as standards.

Results: The amounts of vitamin E and beta-carotene were below the sensitivity threshold of the method, and the content of vitamins C and flavonoids varied over a wide range (vitamins C 2.15- 56.1, (+)-catechin 0-620.3; quercetin 0-10.55; trans-resveratrol 0-5.89 mg/L).

Conclusion: The chromatographic analysis of vitamins and flavonoids allowed us to investigate not only the content of useful substances that make up red wines but also to identify counterfeit products. In this study, wines presented directly to retailers were analyzed since the task was both to determine vitamins and flavonoids and to identify counterfeits. The results of our study showed that among all the selected wine brands, there were no samples that, in terms of their properties, would not meet the required parameters.

Introduction: Cherry-red tobacco is a flue-cured variant that possesses a distinctive “sticky rice” flavor, which is highly valued by the tobacco industry. However, the value of cherryred tobacco is dubious due to the possible health risks associated with tobacco-specific nitrosamines (TSNAs).

Objective: This study aimed to investigate the chemical origin of the “sticky rice” flavor and to assess the potential health hazards of TSNAs.

Methods: An optimized untargeted analysis with gas chromatography-mass spectrometry and a targeted analysis with liquid chromatography-tandem mass spectrometry were conducted.

Result: Over one hundred compounds were identified and quantified. Cherry-red tobacco and the normal control showed significant differences in forty-three of these compounds. Pyridine alkaloids and their derivatives constituted the main difference. Nornicotine, a demethylated product of nicotine in cherry-red tobacco, was confirmed to be pyrolyzed to 3-ethylpyridine, 3-methylpyridine, and other homologues, and transferred to the smoke during smoking. The smoke of cherry-red tobacco was found to contain much higher levels of N’-nitrosonornicotine, a TSNA derived from nornicotine, than that of normal flue-cured tobacco, while the levels of the other detected TSNAs were lower. The two types of tobacco had similar total amounts of the four TSNAs.

Conclusion: The pyrolysis of nornicotine into 3-ethylpyridine and its homologues during smoking may be the main cause of the “sticky rice” flavor of cherry-red tobacco. The level of TSNAs does not reflect the difference in health risk between cherry-red tobacco and the control.

Background: Rutin is a natural flavonol that showed excellent antiglycation activity with an IC50 value of 294.5 ± 1.5 μM. In the current study, three selected plant species of Euphorbia, i.e., Euphorbia helioscopia, Euphorbia larica, and Euphorbia wallichii, were analyzed for the quantification of rutin. Methods: The quantification was done through a newly developed method of Emission spectroscopy coupled with Partial Least Square Regression (PLSR) and UV-visible spectroscopy as a parallel cross-validation method. Results: The spectroscopic results indicated the highest rutin concentration in the roots of E. helioscopia (11.25 mg/100 g) followed by roots of E. wallichii (9.93 mg/100 g), leaves of E. helioscopia and the whole plant of E. larica (9.41 mg/100 g). The leaves of E. wallichii (8.66 mg/100 g) were found to contain the lowest concentration of rutin among all the tested samples. Conclusion: The present method is one of the simple, robust, and non-destructive methods to carry out the quantitative estimation of rutin in plants.

Background: Scutellariae Radix, one of the most widely used herbs in Traditional Chinese Medicine, exhibits various biological activities due to its chemical components, which stand out for a number of flavonoids. In this study, Ultrasound-assisted aqueous two-phase extraction (UAATPE) was employed for the first time to obtain a high extraction rate and high purity of flavonoids from Scutellariae Radix.

Methods: The Box-Behnken response surface method (RSM) was utilized to optimize the extraction conditions with the application of the new aqueous two-phase system (ATPS) composed of ethanol and ammonium sulfate. The major influence factors, including ethanol concentration, ammonium sulfate concentration, liquid-to-solid ratio, sonication time, and extraction temperature, were investigated by the single-factor experiment. The compositional characterization of flavonoids was characterized with HPLC-UV. Scanning electron microscopy (SEM) was applied to research the surface morphology of raw material. Furthermore, the bioactivities of the extract obtained by UA-ATPE were studied in vitro.

Results: The optimal extraction conditions were as follows: the ethanol content was 26.12% (w/w), the ammonium sulfate content was 20.02% (w/w), the liquid-to-solid ratio was 40 mL/g, the sonication time was 5 min with the ultrasonic power of 250 W, and the operating process was performed at room temperature. Compared with the traditional extraction methods, UA-ATPE exhibited higher extraction efficiency and better extraction selectivity. The DPPH and ABTS radical scavenging tests showed that enriched products possessed strong antioxidant activity.

Conclusion: The study confirmed that the developed method of UA-ATPE could be used as an efficient, eco-friendly, and low-consumption method for the extraction and purification of flavonoids from Scutellariae Radix.