Short communication

Gas chromatographic/mass spectrometric profiling of luteolin and its metabolites in rat urine and bile

Although most of the composite based electrocatalysts for determination of luteolin has been developed, the unsatisfactory limit of detection (LOD) and narrow linear range originated from the unstable interface among each component limit their further application. Herein, a SnO₂ quantum dots modified glass carbon electrode (SnO₂ QDs/GCE) is developed for selective detection of luteolin. The electrochemical behavior of luteolin on SnO₂ QDs/GCE indicates that the redox process involves participating of two-electrons/double-protons. The big specific surface area of SnO₂ QDs provides sufficient active sites for the redox reaction of luteolin. On this bases, an ultra-low LOD of 0.25 nM as well as a large linear range of 0.1–1200 nM is obtained for detection of luteolin. Besides, the influence of several coexisting compounds and common ions on the detection of luteolin was evaluated, and no obvious interference was found. Finally, the SnO₂ QDs/GCE electrode achieves accurate detection of luteolin in actual samples including orange, lemon and carrot juices. This work provides new strategy for the determination of luteolin in complex systems.

As a common antioxidant and antimicrobial agent in plants, luteolin has a variety of pharmacological activities and biological effects, the ability to specifically bind proteins and thus inhibit novel coronaviruses and treat asthma. Here, Co doped nitrogen-containing carbon frameworks/MoS₂−MWCNTs (Co@NCF/MoS₂−MWCNTs) nanocomposites have been synthesized and successfully applied to electrochemical sensors. X-ray photoelectron spectroscopy, scanning electron microscopy and X-ray diffraction were used to examine the morphology and structure of the samples. Meanwhile, the electrochemical behavior of Co@NCF/MoS₂−MWCNTs was investigated. Due to its excellent electrical conductivity, electrocatalytic activity and adsorption, it is used for the detection of luteolin. The Co@NCF/MoS₂−MWCNTs/GCE sensor can detect luteolin in a linear range from 0.1 nM to 1.3 μM with a limit of detection of 0.071 nM. Satisfactory results were obtained for the detection of luteolin in natural samples. In addition, the redox mechanism and electrochemical reaction sites of luteolin were investigated by the scan rate of CV curves and density functional theory. This work demonstrates for the first time the combination of ZIF-67-derived Co@NCF and MoS₂−MWCNTs as electrochemical sensors for the detection of luteolin, which opens a new window for the sensitive detection of luteolin.

Electrochemical determination of luteolin is vital to food industry owing to its bioactive properties such as anti-viral, anti-ulcer. However, bare electrode of traditional electrochemical sensors generally have narrow linear range and low sensitivity, which sets limit on their practical application. Accordingly, a new nano-architecture fabricated with Ag doped CoNi-bimetal metal–organic frameworks (Ag-CoNi-MOF) is developed as a material for electrochemical determination of luteolin. The introduction of Ag to three-dimensional (3D) flower-like hierarchical structure greatly increases specific surface area and electrical conductivity, which subsequently provides more excellent active sites for luteolin oxidation. Under optimal conditions, Ag-CoNi-MOF sensor presents a broader linear response to luteolin concentration of 0.002 – 1.0 μM with the detection limit as low as 0.4 nM (S/N = 3). Ag-CoNi-MOF has good anti-interference according to compared amperometric current response of luteolin within different organic analytes and metal ions. Finally, the sensor platform is implemented directly to determine luteolin in human urine for evaluation of its practical application. In general, Ag-CoNi-MOF sensors fabricated perform larger linear range with high sensitivity and anti-interference properties, which can be used as a potential material for electrochemical determination of luteolin.

A novel electrochemical sensor was constructed based on three-dimensional NiO@Ni-MOF nanoarrays modified Ti mesh (NiO@Ni-MOF/TM). NiO nanoarrays were firstly produced on conductive TM using hydrothermal and carbonization method, and then Ni-MOFs were directly grown on the surface of NiO nanoarrays through self-template strategy. The morphology and structure of the prepared materials were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The as-prepared NiO@Ni-MOF/TM was used as electrochemical sensor for investigating electrochemical behaviors of luteolin flavonoid. The composite electrode combined the excellent enrichment ability of Ni-MOF, high catalysis of NiO nanoarrays with the superior electronic conductivity of TM substrate, enabling ultra-sensitive detection towards luteolin with a low limit of detection (LOD) of 3 pM (S/N = 3). Besides, with favorable stability and selectivity, the fabricated sensor was applied in the determination of luteolin in actual samples with satisfactory results.

In this work, a novel core-shell structured magnetic covalent organic frameworks (denoted as Fe₃O₄@TAPB-DMTP-COFs (TAPB, 1,3,5-tris(4-aminophenyl)benzene; DMTP, 2,5-dimethoxyterephaldehyde) was fabricated via a facile step-by-step assembly approach. The resulting material was characterized by transmission electron microscopy, powder X-ray diffraction, Fourier transform-infrared spectroscopy, X-ray photoelectron spectroscopy and voltammetric methods. Fe₃O₄@TAPB-DMTP-COFs was further coated on the surface of glassy carbon electrode to construct an electrochemical sensor for the determination of luteolin. TAPB-DMTP-COFs with highly ordered porous structure not only provide more active sites, but also avoid the aggregation of Fe₃O₄. Meanwhile, Fe₃O₄ magnetic nanoparticles can obviously accelerate the electron transport. Under the optimal conditions, the method displayed low detection limit (0.0072 μmol L⁻¹), wide linear range (0.010–70 μmol L⁻¹), and good recoveries (98.5–102.0%). Moreover, there are no significant effects from the interferents. The feasibility of this method was applied to trace luteolin in chrysanthemum tea and carrot. We consider this COFs-based porous material would become one of the most promising materials in electrochemical sensor.

A simple and sensitive electrochemical sensor based on graphene quantum dots (GQDs) and gold nanoparticles (GNPs) nanocomposite modified glassy carbon electrode (GQDs/GNPs/GCE) was developed for the determination of luteolin. The GQDs/GNPs/GCE was prepared by electrodeposition method, and characterized by scanning electron microscopy and electrochemical impedance spectroscopy. The GQDs/GNPs nanocomposite showed excellent synergistic electrochemical activity for the oxidation of luteolin. Compared to bare GCE, the GQDs/GNPs/GCE resulted in a 16-fold increase in the oxidation current of luteolin in phosphate buffer at pH 5.0. Using the differential pulse voltammetry method, the dependence of the oxidation current vs. concentration was found to be linear from 1 × 10⁻⁸ to 1 × 10⁻⁵ M with a regression coefficient of 0.997, and the detection limit of luteolin was 1.0 nM (S/N = 3). The recovery was between 98.8% and 101.4% in peanut hull samples. This strategy might enable more opportunities for the electrochemical determination of luteolin in practical applications.