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The extracts and melanins of chaga (Inonotus obliquus (Pers.) Pil.) obtained by raw material pretreatment with high-frequency capacitive low-pressure plasma (RF-plasma) under different technological conditions were studied. The advantages of RF-plasma treatment of raw materials in three different plasma-forming media (argon, air, and nitrogen) were shown. In all cases, the modification of the natural particles surface affecting the extraction process was observed. Optimization of the extraction parameters demonstrated that best results (increase of the extractive compounds yield and higher antioxidant capacity) were achieved with the air-based plasma. The surface topology of the melanins under investigation was evaluated by atomic force microscopy (AFM). The difference of melanins structural features by roughness degree, height, and diameter of single particles in relation to the raw material RF-plasma treatment mode was shown that enabled a deeper insight into the nature of fungal melanins. Preliminary RF-plasma treatment of raw material can be recommended for Inonotus obliquus (Pers.) Pil. extraction while producing medications on their basis.

The working conditions of naringin electropolymerization on the glassy carbon electrode modified with multi-walled carbon nanotubes (MWNT/GCE) under the conditions of potentiodynamic electrolysis have been found. The effect of monomer concentration, polarization window, potential scan rate, and number of cycles on the electrochemical properties of the polynaringin-modified electrode has been evaluated using hexacyanoferrate(II) ions as a redox standard. The best results have been observed for the polymeric coverage obtained from 0.20 mM naringin by tenfold potential cycling in the range of 0.2–0.8 V at a scan rate of 75 mV/s in the Britton-Robinson buffer solution, pH 8.0. The surface of the glassy carbon and modified electrodes has been characterized by scanning electron microscopy, cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. The high porosity of the polynaringin layer leads to an increase of the electrode effective surface area in comparison to GCE (8.2 ? 0.3 and 12.6 ? 0.6 mm2 for GCE and polynaringin/MWNT/GCE, respectively). The electrochemical impedance spectroscopy data indicate an increase of the electron transfer rate on the polynaringin-modified electrode in comparison to GCE and MWNT/GCE (6.0 ? 0.5 kΩ vs. 181 ? 5 and 6.8 ? 0.3 kΩ, respectively).

2,2-di(4-tert-octylphenyl)-1-picrylhydrazyl (DTOPPH?) immobilized on the electrode surface has been proposed as a reagent for the evaluation of antioxidant activity (AOA). The electroreduction parameters of DTOPPH? immobilized on glassy carbon electrode (GCE) modified with carbon nanotubes, cerium and tin dioxide nanoparticles dispersed in surfactants have been studied. The best characteristics (system reversibility and maximal reduction currents) have been obtained on the electrode modified with cerium dioxide nanoparticles and cetylpyridium bromide (CPB). The reduction currents of the immobilized DTOPPH? are decreased in the presence of the phenolic antioxidants allowing application of the electrode created for their AOA evaluation. Five minutes have been shown to be enough for the reaction of antioxidants with the immobilized DTOPPH?. AOA evaluation has been performed under conditions of differential pulse voltammetry. ЕC50 parameter for tannin, quercetin, catechin and ferulic acid has been found and compared with that one based on the reaction with 2,2-diphenyl-1-picrylhydrazyl under the same conditions. The approach developed has been applied for the evaluation of AOA in juices and nectars.

Optimization of the RF-plasma treatment modes of chaga raw materials using the Statistica 6.0 software package has been performed. Mathematical design has been carried out to calculate the optimum parameters of RF-plasma treatment using three plasma-forming gases – argon, air, and nitrogen. Plasma treatment of chaga raw materials has been undertaken at the constant parameters: pressure P = 30.0 Pa, anodic current J = 0.7 A, gas consumption G = 0.04 g/s; the variable parameters were power U = 5.0÷7.0 kV and treatment duration at the high-frequency capacitor category of the lowered pressure t = 30÷60 min. Optimization of four key parameters for extraction of chaga raw materials (solid residue, melanin yield, antioxidant activity of both extract and chaga melanin) depending on the chosen plasma-forming gas (argon, air, or nitrogen) has been achieved. The optimum modes of RF-plasma treatment allowing to obtain the extracts and melanin of chaga mushroom with the improved physicochemical and antioxidant characteristics have been calculated.

High-frequency capacitive discharge (RF plasma) at low pressure was used as preliminary stage for the intensification of extraction from natural medicinal raw material. RF-plasma treatment was carried out in two modes differed by the nature of plasma-forming gas. Chaga (Inonotus obliquus (Pers.) Pil.) known as the birch mushroom was selected as a perspective source of raw material. Extraction was carried out in two ways – remaceration and maceration. The analy-sis of chaga extracts and melanins was performed using traditional techniques including determination of physical and chemical, antioxidant and spectral characteristics. The obtained extracts and melanins were compared to the control samples and literature data. RF-plasma treatment of medicinal raw material increased the yield of extractive substances, in particular of the main active component of chaga – melanin. The antioxidant activity of chaga extracts grew, while for melanins it remained at the level similar to that of control samples. The IR spectral characteristics of the studied chaga melanins are similar and agree well with the literature data. Insignificant deviations in the position and intensity of absorption strips were observed for the samples after RF treatment. IR spectra of the studied chaga melanins are similar to those for mushroom melanins, thereby confirming the similarity in their nature. RF-plasma treatment of chaga medicinal raw materials allows to modify them partially. The structural and mechanical properties of melanins modified by RF plasma remain the same.

The oxidation potentials of micellar spice extracts on a glassy carbon electrode modified with cerium dioxide nanoparticles in the Brij®35 micellar medium in phosphate buffer solution have been found. A chronoamperometric approach for evaluation of the antioxidant capacity (AOC) of micellar spice extracts based on the oxidation of their antioxidants under the conditions of potentiostatic electrolysis at 1.1 V has been developed. It has been shown that steady-state electrolysis is attained in 100 s. The AOC has been expressed in gallic acid equivalents recalculated per 1 g of dry spices. The dynamic analytical range of gallic acid was 7.50–2500 μM with the limits of detection and quantification of 2.27 and 7.50 μM, respectively. The approach has been tested on the extracts of 20 spices. Their AOC varied in a wide range (from 109.0 ± 0.2 mg/g for clove to 1.9 ± 0.1 mg/g for caraway) owing to the composition and contents of active components in raw plant materials. Positive correlations have been found between the AOC of spices and their antioxidant activity based on the reaction with 2,2-diphenyl-1-picrylhydrazyl (r = 0.8990 at rcrit = 0.497) and ferric reducing power (r = 0.9066 at rcrit = 0.497).