Kinetics and Mechanism of Epinephrine Autoxidation in the Presence of Plant Superoxide Inhibitors: A New Look at the Methodology of Using a Model System in Biological and Chemical Research.

Superoxide is the primary active oxygen form produced in living organisms. Because of superoxide anion radical formation during epinephrine oxidation in alkaline medium, this system is offered in some works for antioxidant activity analysis, however, without enough physicochemical justification. Therefore, the task of developing reliable methods for analyzing the superoxide inhibition activity of various objects is very urgent. In this work, a kinetic model of epinephrine autoxidation in an alkaline medium in the presence of antioxidants of plant origin is proposed. The participation of chain reactions with long oxidation chains in this process is revealed. The limiting stage of the process is a one-electron reduction of oxygen by the anionic forms of the phenolic hydroxyls of epinephrine. The appearance of the absorption maximum at a wavelength of 347 nm during epinephrine autoxidation is associated with adrenolutin formation, which is confirmed by HPLC/UV/MS. No adduct formation between phenolic antioxidants and epinephrine oxidation products was found. The complex U-shaped character of epinephrine autoxidation rate dependence on the content of antioxidants in the reaction system was shown. The study of the kinetics of epinephrine autoxidation in the presence of an individual phenolic plant superoxide inhibitor, chlorogenic acid, was carried out for the first time. The inhibitory effect of yarrow, chamomile, and bur beggar-ticks plant extracts in the adrenaline system was examined.

Nerve agent markers screening after accumulation in garden cress (Lepidium sativum) used as a model plant object.

In this research an accumulation of nerve agent markers in garden cress (Lepidium sativum) as a model plant object was studied using LC-QTOF hybrid system. For the determination of methylphosphonic acid and alkyl methylphosphonates, which are specific markers of sarin, soman, VR and VX, simple and sensitive approach was developed. Direct analysis of aqueous extracts on the reversed phase column with polar endcapping allowed to achieve satisfactory retention factor for methylphosphonic acid, which has high polarity and is usually very weakly retained on the ordinary reversed phase columns. Application of the QTOF mass spectrometer with high mass resolution led to the increase in the accuracy of the conducted measurements. The HPLC-HRMS technique developed exclusively for this study has been validated for linearity, limit of detection, limit of quantification, precision, accuracy and matrix effect prior to the analysis of plant extract samples. Hydroponic growth model was employed to examine accumulation of nerve agent markers in garden cress. It was found that after elimination of nerve agent markers from the plant growth medium, garden cress was able to store these substances for at least 5 weeks providing high retrospectivity of the analysis. Moreover, during the cress growth, no metabolization of alkyl methylphosphonates was observed. This allows not only to reveal the fact of nerve agents release into environment, but also to define its type after a long period of time.

Unified strategy for HPLC-MS evaluation of bioactive compounds for quality control of herbal products.

Evaluation of safety, quality and composition of herbal products and food supplements based on botanical ingredients is a matter of serious concern. For screening of botanicals in herbal products multitargeted and group-targeted approaches may be applied. In the group-targeted approach botanicals are characterized by means of an appropriate group of structurally related biomarkers compared with the multitargeted approach where a number of selected analytes are monitored based on a multiple reaction monitoring survey. In this study a unified strategy for quality control of herbal products was developed on the basis of fast ultrasound-assisted extraction, chromatographic separation and mass spectrometric quantification of bioactive compounds. A large list of unique biomarkers were monitored under almost identical chromatographic conditions, while an efficient strategy for HPLC-MS group-targeted analysis was also developed for comprehensive evaluation of chemical composition of botanicals intensively used for herbal product manufacturing. In the latter case, structurally close compounds were determined in a single ion monitoring mode for the characteristic group of fragment ions, allowing fast profiling and quality assessment of the plant material or complex food supplement. The sensitivity of the developed approaches was on the level of 1-50 ng/mL, which is higher than that of existing HPLC-UV quality control methods.