Abstract
International comparisons in organic analysis (OA) are organized and coordinated by the Organic Analysis Working Group (OAWG) of the Consultative Committee for Amount of Substance (CCQM). ...OAWG also performs strategic planning and highlights the focus areas and challenges in OA. Realizing well that the amount of organic compounds and potential combinations of analyte-matrix is numerous, the OAWG has developed a systematic approach to the comparisons organizing. This approach allows to comprehensively describe the specifics of each comparison and appropriate features combination allows to cover all relevant aspects of OA. In terms of CMCs submission, recently the new concept has been created suggesting a broader view on the NMIs competence – it is the concept of “Broad Scope Claims” (BCs). BCs allow NMIs to submit CMCs for a wider range of analytes and matrices. In 2021 the OAWG has highlighted the priority areas for activities and promising methods and technologies for the OA for the period up to 2030.
In international comparisons on OA Russia is represented by VNIIM. Since 1998 VNIIM has been taking part in more than 35 comparisons covering various aspects of OA. Each successful comparison is a real and documented confirmation of Russia competence in the relevant OA area. At the moment 89 CMCs are presented in the Database, including 25 BCs.
The paper considers the effects of plant triterpenoid betulin and its derivative betulonic acid on rat liver mitochondria and liposomes. It was found that betulonic acid and, to a lesser extent, ...betulin, activate mitochondrial respiration in states 2 and 4 and inhibit ADP- and DNP-stimulated (uncoupled) respiration. The effect of betulonic acid resulted in a significant decrease of the respiratory control and ADP/O ratios and decrease in Δψ. The effects of both compounds were most pronounced in the case of succinate-fueled mitochondrial respiration. This may include both the possible protonophore effect of betulonic acid and the inhibition of respiratory chain complexes by both compounds. Both agents enhanced H2O2 production in succinate-fueled mitochondria, while betulonic acid exerted an antioxidant effect with NAD-dependent substrates. Betulin was found to induce mitochondrial aggregation, but had no effect on membrane permeability. A similar pattern was found on liposomes. As revealed by the laurdan generalized polarization (GP) technique, betulin increased laurdan GP in lecithin liposomes, indicating a decrease in membrane fluidity. Measurements of GP as a function of fluorescence excitation wavelength gave an ascending line for high concentrations of betulin, which can be interpreted as phase heterogeneity of the lipid/betulin system. High concentrations of betulin (> 60 mol%) was also demonstrated to cause permeabilization of lecithin liposomes. Betulonic acid was much less effective in inducing the aggregation of mitochondria and liposomes and had no effect on membrane permeability. The possible mechanisms of betulin and betulonic acid effect on rat liver mitochondria and liposomes are discussed.
•Betulin and BTA inhibit oxidative phosphorylation in rat liver mitochondria.•Betulin and BTA affect H2O2 production by mitochondria.•Laurdan fluorescence indicates a phase heterogeneity in lipid/betulin (BTA) system.•Betulin and BTA induce aggregation of mitochondria and liposomes.
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