Ratiometric fluorescence detection of artemisinin based on photoluminescent Zn-MOF combined with hemin as catalyst

Artemisinin (ART) is a type of frontline drug to treat drug-resistant falciparum malaria. Simple, accurate and selective determination of ART is significant to monitor its clinical pharmaceutical efficacy. Herein, a new ratiometric fluorescence method has been designed for the determination of ART with Zn-MOF as fluorescence reference and hemin as catalyst, respectively. Zn-MOF possesses intrinsic fluorescence at 443 nm owing to 2-aminoterephthalic acid ligand. When o-phenylenediamine (OPD) is mixed with hemin, a weak fluorescent signal at 570 nm ascribed to oxidized product of OPD (oxOPD) is observed. In the presence of ART, hemin can catalyze ART to break its peroxide bridge and release a large number of reactive oxygen species, which effectively oxidize OPD into luminescent oxOPD. Therefore, the fluorescence at 570 nm is enhanced significantly while the fluorescence of Zn-MOF remains basically unchanged. Thus, a ratiometric fluorescence sensing platform has been constructed for the detection of ART. This method exhibits wider linear range (0.15 μM-150 μM) with detection limit of 50 nM. This novel and selective method has been used to detect ART in compound naphthoquinone phosphate tablets.

Detection of ascorbic acid based on its quenching effect on luminol-artemisinin chemiluminescence

We find that luminol can react with artemisinin (ART) to produce chemiluminescence (CL) in the absence of a catalyst and ascorbic acid (AA) can quench luminol-ART CL. Based on its efficient inhibition effect on luminol-ART CL, a new AA detection method is established. The calibration curve for the determination of AA is in the linear range of 5 × 10^-7 M to 1 × 10^-4 M with a detection limit of 50 nM, which is more sensitive than many other reported methods. This CL approach was utilized to detect AA in vitamin C tablets by applying the standard addition method, and the recoveries of 104.0%, 96.8% and 103.4% were obtained, respectively, at concentrations of 1 μM, 5 μM and 10 μM with a RSD value of less than 3.6%. This developed method for AA assay is distinguished by its fastness, reproducibility, easy operation and good selectivity.

A novel and sensitive fluorescent assay for artemisinin with graphene quantum dots based on inner filter effect

The authors describe a novel method for the determination of artemisinin (ART) by using graphene quantum dots (GQDs) as the fluorescent probes. This method is based on the fact that ART can react with p-aminophenylboronic acid (p-ABA) to produce p-aminophenol (p-AP). While in the presence of tyrosinase (TYR), p-AP can be oxidized into 4-amino-1,2-benzoquinone, which effectively quenched the fluorescence of GQDs due to the inner filter effect (IFE). By making use of these reactions, a novel and sensitive fluorescent assay for ART has been developed. The calibration curve for the determination of ART is linear in the range of 0.1-5 μM and 5-55 μM with the detection limit of 33 nM, which is more sensitive than most of other methods. Some common coexisting substances including Ca²⁺, Na⁺, Mg²⁺, K⁺, PO₄^3-, starch, lactose, dextrin, and magnesium stearat have negligible effects on the fluorescence intensity of GQDs-TYR-p-ABA system. Finally, the sensing system was successfully applied to the detection of the compound naphthoquine phosphate tablet samples with satisfactory recoveries. This IFE-based GQDs fluorescence sensing strategy is facile and sensitive for the determination of ART because neither the surface modification nor the linking between the receptor and the fluorophore is required.

A Diol-Based-Matrix Solid-Phase Dispersion Method for the Simultaneous Extraction and Determination of 13 Compounds From Angelicae Pubescentis Radix by Ultra High-Performance Liquid Chromatography

A simple and eco-friendly Diol-based-matrix solid-phase dispersion method (MSPD) was optimized and established to simultaneously extract 13 bioactive compounds (7 coumarins and 6 phenolic acids) in Angelicae Pubescentis Radix (APR) by ultrahigh performance liquid chromatography coupled with photodiode array detector (UHPLC-PDA). Diol was chosen as the dispersing sorbent and methanol solution was used as the elution solvent. The preparation procedures for the MSPD including the types of sorbents, mass ratio of matrix to sorbent, grinding time, type, concentration and volume of elution solvent were investigated. Under the optimal conditions, good recoveries of the 13 target compounds were obtained in the range of 94.8-107% (RSD < 3.22%). The limits of detection (LODs) and limits of quantitation (LOQs) were in the ranges of 0.08-0.12 μg mL^-1 and 0.16-0.24 μg mL^-1, respectively. Compared with the traditional method, it was a green and environmentally friendly technique. The results proved that the established method was successfully applied to the extraction and determination of 13 target bioactive compounds for quality control in APR.

A Simple Method for the Screening and Measurement of Phenols in Dendrobium chrysotoxum by a Miniature Mass Detector Using a Matrix Solid-Phase Dispersion Method

The present study aims at building a miniature mass method for the simultaneous determination of 12 phenols including the subtypes of bibenzyl, phenanthrene, and fluorenone, which was used to evaluate the quality of Dendrobium chrysotoxum. Through the full scan mode, new compounds were elucidated. The new compounds were quantified by carrying out the analysis of the ratio of the standard solution areas to new compound areas versus analyte concentration. The limit of detection (LOD) and limit of quantification (LOQ) for phenols were 0.5 µg/mL-1 µg/mL and 1 µg/mL-2 µg/mL, respectively. Average recoveries of phenols were ranged from 83.2% to 97.5%. Reproducibility represented by the RSD percentage was from 2.3% to 8.7%. The average content of the four analytes, erianin, chrysotobibenzyl, confusarin, and moscatilin, were more than 200 mg/kg, and the content of bibenzyl compounds was found to be the highest in Dendrobium chrysotoxum. Among these bibenzyl compounds, erianin was determined as the typical chemical marker from Dendrobium chrysotoxum. The newly established UPLC with a miniature mass detector method was found to be an appropriate tool for the quality assessment of Dendrobium chrysotoxum.

Simultaneous Extraction and Determination of Compounds With Different Polarities From Platycladi Cacumen by AQ C18-Based Vortex-Homogenized Matrix Solid-Phase Dispersion With Ionic Liquid

This study presented a rapid, simple and environmentally friendly method of employing AQ C₁₈-based vortex-homogenized matrix solid-phase dispersion with ionic liquid (AQ C₁₈-IL-VHMSPD) for the extraction of compounds with different polarities from Platycladi Cacumen (PC) samples by ultra high-performance liquid chromatography with PDA detection. AQ C₁₈ (aqua C₁₈) and ionic liquid ([Bmim]BF₄) were used as the adsorbent and green elution reagent in vortex-homogenized MSPD procedure. The AQ C₁₈-IL-VHMSPD conditions were optimized by studying several experimental parameters including the type of ionic liquid, the type of adsorbent, ratio of sample to adsorbent, the concentration and volume of ionic liquid, grinding time and vortex time. The recoveries of the target compounds were in the range of 96.9-104% with relative standard deviation values no more than 2.8%. The limits of detection and limits of quantitation were in the range of 0.2-1.2 and 1.0-5.4 ng mL^-1, respectively. Compared with the traditional ultrasonic-assisted extraction, the developed AQ C₁₈-IL-VHMSPD method required less sample, reagent and time. It was concluded that the AQ C₁₈-IL-VHMSPD method was a powerful method for the extraction and quantification of the high polarity and low polarity compounds in traditional Chinese medicines samples.

Non-ionic detergent Triton X-114 Based vortex- synchronized matrix solid-phase dispersion method for the simultaneous determination of six compounds with various polarities from Forsythiae Fructus by ultra high-performance liquid chromatography

A simple nonionic detergent - based vortex- synchronized matrix solid-phase dispersion (ND-VSMSPD) method was developed to extract bioactive compounds in Forsythiae Fructus coupled with ultra high-performance liquid chromatography (UHPLC). Nonionic detergent Triton 114 was firstly used as a green elution reagent in vortex- synchronized MSPD procedure. The optimum parameters were investigated to attain the best results, including Florisil as sorbent, 2mL 10% (v/v) nonionic detergent Triton X-114 as the elution reagent, 1:1 of sample/sorbent ratio, grinding for 3min, and whirling for 2min. The recoveries of the six compounds in Forsythiae Fructus were in the range of 95-104% (RSD <4.6%) and the method displayed a good linearity within the range of 0.08-20μgmL^-1 for caffeic acid, 0.6-150μgmL^-1 for forsythoside A, 0.4-100μgmL^-1 phillyrin, 0.2-50μgmL^-1 for quercetin, isorhamnetin and arctigenin (r≥0.999). It was proved that the extraction yields of almost all compounds attained by the established vortex- synchronized MSPD, which required lower sample, reagent and time, were higher than the normal MSPD and the traditional ultrasonic-assisted extraction. Consequently, this developed vortex- synchronized MSPD coupled with simple UHPLC method could be efficiently applies to extract and analyze the target compounds in real Forsythiae Fructus samples.

Sensitive and selective electrochemical detection of artemisinin based on its reaction with p-aminophenylboronic acid

The electrochemical detection of artemisinin generally requires high oxidation potential or the use of complex electrode modification. We find that artemisinin can react with p-aminophenylboronic acid to produce easily electrochemically detectable aminophenol for the first time. By making use of the new reaction, we report an alternative method to detect artemisinin through the determination of p-aminophenol. The calibration curve for the determination of artemisinin is linear in the range of 2 μmol L(-1) to 200 μmol L(-1) with the detection limit of 0.8 μmol L(-1), which is more sensitive than other reported electrochemical methods. The relative standard deviation is 4.83% for the determination of 10 μM artemisinin. Because the oxidation potential of p-aminophenol is around 0 V, the present method is high selective. When 40 μM, 90 μM and 140 μM of artemisinin were spiked to compound naphthoquine phosphate tablet samples, the recoveries are 107.6%, 105.4% and 101.7%, respectively. This detection strategy is attractive for the detection of artemisinin and its derivatives. The finding that artemisinin can react with aromatic boronic acid has the potential to be exploited for the development of other sensors, such as fluorescence artemisinin sensors.

Natural polyhydroxyalkanoate-gold nanocomposite based biosensor for detection of antimalarial drug artemisinin

The worrisome trend of antimalarial resistance has already highlighted the importance of artemisinin as a potent antimalarial agent. The current investigation aimed at fabricating a biosensor based on natural polymer polyhydroxyalkanoate-gold nanoparticle composite mounting on an indium-tin oxide glass plate for the analysis of artemisinin. The biosensor was fabricated using an adsorbing horse-radish peroxidase enzyme on the electrode surface for which cyclic voltammetry was used to monitor the electro-catalytic reduction of artemisinin under diffusion controlled conditions. Electrochemical interfacial properties and immobilization of enzyme onto a polyhydroxyalkanoate-gold nanoparticle film were evaluated, and confirmed by cyclic voltammetry, electrochemical impedance spectroscopy and scanning electron microscopy. The differential pulse voltammetric peak current for artemisinin was increased linearly (concentration range of 0.01-0.08μg mL(-1)) with sensitivity of 0.26μAμg mL(-1). The greater sensitivity of the fabricated biosensor to artemisinin (optimum limits of detection were 0.0035μg mL(-1) and 0.0036μg mL(-1) in bulk and spiked human serum, respectively) could be of much aid in medical diagnosis.

LC-UV/MS quality analytics of paediatric artemether formulations

A highly selective and stability-indicating HPLC-method, combined with appropriate sample preparation steps, is developed for β-artemether assay and profiling of related impurities, including possible degradants, in a complex powder for oral suspension. Following HPLC conditions allowed the required selectivity: a Prevail organic acid (OA) column (250 mm×4.6 mm, 5 μm), flow rate set at 1.5 mL/min combined with a linear gradient (where A=25 mM phosphate buffer (pH 2.5), and B=acetonitrile) from 30% to 75% B in a runtime of 60 min. Quantitative UV-detection was performed at 210 nm. Acetonitrile was applied as extraction solvent for sample preparation. Using acetonitrile-water mixtures as extraction solvent, a compartmental behaviour by a non-solving excipient-bound fraction and an artemether-solubilising free fraction of solvent was demonstrated, making a mobile phase based extraction not a good choice. Method validation showed that the developed HPLC-method is considered to be suitable for its intended regulatory stability-quality characterisation of β-artemether paediatric formulations. Furthermore, LC-MS on references as well as on stability samples was performed allowing identity confirmation of the β-artemether related impurities. MS-fragmentation scheme of β-artemether and its related substances is proposed, explaining the m/z values of the in-source fragments obtained.

Pharmacokinetics and tissue distribution study of scoparone in rats by ultraperformance liquid-chromatography with tandem high-definition mass spectrometry

Scoparone is an important constituent of Yinchenhao (Artemisia annua L.), a famous Chinese medicinal plant, and has several known bioactivities, and displayed bright prospects in prevention and therapy of jaundice and liver disorders. The aim of this study was to investigate the in vivo plasma pharmacokinetic and tissue distribution characteristics of scoparone after oral administration. The levels of scoparone in plasma, and tissues were measured by a rapid and sensitive UPLC-MS/MS method. The biosamples were prepared using methanolic precipitation and the separation of scoparone was achieved on a UPLC HSS T3 column by linear gradient elution using water (containing 0.1% formicacid) and acetonitrile (containing 0.1% formic acid) as the mobile phase at a flow rate of 0.5mL/min The total run time was only 3.9min. Our results successfully demonstrate that this method has excellent and satisfactory selectivity, sensitivity, linearity, precision, accuracy and recovery. The estimated pharmacokinetic parameters (i.e., C(max), AUC and CL), were C(max)=14.67mg/L, AUC=81.15mg*h/L, CL=1.23L/h for scoparone. The pharmacokinetic study found that scoparone was distributed and eliminated rapidly in rats. Tissue distribution showed the highest level was observed in liver, followed by the kidney and spleen; the lower level appeared in the muscle, thyroid, and adrenal. It was not detected in the brain which indicated that scoparone does not cross the blood-brain barrier after oral administration. Our developed method was suitable for the study on pharmacokinetics and tissue distribution of scoparone after oral administration.