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A sensitive wall-jet/thin-layer amperometric electrochemical detector (ECD) coupled to high-performance liquid chromatography (HPLC) was developed for simultaneous determination of guanine (G) and adenine (A). The analytes were detected at a glassy carbon electrode (GCE) and the HPLC−ECD calibration curves showed good linearity ( R 2 >0.997) under optimized conditions. Limits of detection for G and A are 0.6 nM and 1.4 nM ( S / N =3), respectively, which are lower than those obtained with an UV–vis detector and a commercial electrochemical detector. We have successfully applied this HPLC−ECD to assess the contents of G and A in hydrochloric acid-digested calf thymus double-stranded DNA. In addition, we compared in detail the analysis of G and A by cyclic voltammetry (CV) and by the HPLC−ECD system on both bare GCE and electroreduced graphene oxide (ERGO) modified GCE. We found that the adsorption of G and A on the electrode surfaces can vary their anodic CV peaks and the competitive adsorption of G and A on the limited sites of the electrode surfaces can cause crosstalk effects on their anodic CV peak signals, but the HPLC−ECD system is insensitive to such electrode-adsorption and can give more reliable analytical results. [ABSTRACT FROM AUTHOR]

Wall-jet/thin-layer amperometric electrochemical detection (ECD) coupled with high-performance liquid chromatography (HPLC) was used here for the simultaneous analysis of dopamine (DA) and homovanillic acid (HVA) at a glassy carbon electrode. Compared with the conventional thin-layer mode and wall-jet mode, the presented wall-jet/thin-layer ECD has the advantages of enhanced capture of electroactive DA and HVA on the working electrode to give enhanced responses and more convenient washing/refreshment of the working electrode surface. Under optimized conditions, the HPLC-ECD calibration curves show good linearity from 0.01 to 100 μM for DA and HVA, and the limits of detection (LODs) obtained were 1.1 nM for DA and 0.7 nM for HVA which are lower than those obtained with an UV-vis detector and a commercial electrochemical detector. The method was tested on human urine with satisfactory results. The balance of response-signal, signal-background and noise level for our HPLC-ECD system is also discussed. In addition, a demethylation electrooxidation mechanism for HVA is suggested through potentiostatic bulk electrolysis, electrospray ionization-mass spectrometry, fluorescent spectrophotometry and cyclic voltammetry studies. [ABSTRACT FROM AUTHOR]

Aconitum carmichaelii is widely used in traditional Chinese medicine clinics as a bulk medicinal material. It has been used in China for more than two thousand years. Nevertheless, the stems and leaves of this plant are usually discarded as non-medicinal parts, even though they have a large biomass and exhibit therapeutic properties. Thus, it is crucial to investigate metabolites of different parts of Aconitum carmichaelii and explore the relationship between metabolites and toxicity to unleash the utilization potential of the stems and leaves. Using plant metabolomics, we aim to correlate different metabolites in various parts of Aconitum carmichaelii with toxicity, thereby screening for toxicity markers. This endeavor seeks to offer valuable insights for the development of Aconitum carmichaelii stem and leaf-based applications. UHPLC-Q-Orbitrap MS/MS-based plant metabolomics was employed to analyze metabolites of the different parts of Aconitum carmichaelii. The cardiotoxicity and hepatotoxicity of the extracts from different parts of Aconitum carmichaelii were also investigated using zebrafish as animal model. Toxicity markers were subsequently identified by correlating toxicity with metabolites. A total of 113 alkaloids were identified from the extracts of various parts of Aconitum carmichaelii , with 64 different metabolites in stems and leaves compared to daughter root (Fuzi), and 21 different metabolites in stems and leaves compared to mother root (Wutou). The content of aporphine alkaloids in the stems and leaves of Aconitum carmichaelii is higher than that in the medicinal parts, while the content of the diester-diterpenoid alkaloids is lower. Additionally, the medicinal parts of Aconitum carmichaelii exhibited cardiotoxicity and hepatotoxicity, while the stems and leaves have no obvious toxicity. Finally, through correlation analysis and animal experimental verification, mesaconitine, deoxyaconitine, and hypaconitine were used as toxicity markers. Given the low toxicity of the stems and leaves and the potential efficacy of aporphine alkaloids, the stems and leaves of Aconitum carmichaelii hold promise as a valuable medicinal resource warranting further development. [Display omitted] • A. carmichaelii stems and leaves: more aporphine, fewer DDAs than medicinal parts. • A. carmichaelii stems and leaves show no apparent toxicity, but medicinal parts do. • The mesaconitine, deoxyaconitine, and hypaconitine were screened as toxicity markers. • Exploring A. carmichaelii waste for medicinal resources holds potential. [ABSTRACT FROM AUTHOR]