Objective. Aminothiols (glutathione (GSH), cysteinylglycine (CG)) may play an important role in the pathogenesis of coronavirus disease 2019 (COVID-19), but the possible association of these indicators with the severity of COVID-19 has not yet been investigated. Methods. The total content ( t ) and reduced forms ( r ) of aminothiols were determined in patients with COVID-19 ( n = 59 ) on admission. Lung injury was characterized by computed tomography (CT) findings in accordance with the CT0-4 classification. Results. Low tGSH level was associated with the risk of severe COVID-19 ( tGSH ≤ 1.5   μ M , mild vs. moderate/severe: risk   ratio   RR = 3.09 , p = 0.007 ) and degree of lung damage ( tGSH ≤ 1.8   μ M , CT < 2 vs. CT ≥ 2 : RR = 2.14 , p = 0.0094 ). The rGSH level showed a negative association with D-dimer levels ( ρ = − 0.599 , p = 0.014 ). Low rCG level was also associated with the risk of lung damage ( rCG ≤ 1.3   μ M , CT < 2 vs. CT ≥ 2 : RR = 2.28 , p = 0.001 ). Levels of rCG ( ρ = − 0.339 , p = 0.012 ) and especially tCG ( ρ = − 0.551 , p = 0.004 ) were negatively associated with platelet count. In addition, a significant relationship was found between the advanced oxidation protein product level and tGSH in patients with moderate or severe but not in patients with mild COVID-19. Conclusion. Thus, tGSH and rCG can be seen as potential markers for the risk of severe COVID-19. GSH appears to be an important factor to oxidative damage prevention as infection progresses. This suggests the potential clinical efficacy of correcting glutathione metabolism as an adjunct therapy for COVID-19.

Objective. S-Adenosylmethionine (SAM) and S-adenosylhomocysteine (SAH) are indicators of global transmethylation and may play an important role as markers of severity of COVID-19. Methods. The levels of plasma SAM and SAH were determined in patients admitted with COVID-19 ( n = 56 , mean   age = 61 ). Lung injury was identified by computed tomography (CT) in accordance with the CT0-4 classification. Results. SAM was found to be a potential marker of lung damage risk in COVID-19 patients ( SAM > 80   nM ; CT3,4 vs. CT 0-2: relative ratio (RR) was 3.0; p = 0.0029 ). SAM / SAH > 6.0 was also found to be a marker of lung injury (CT2-4 vs. CT0,1: RR = 3.47 , p = 0.0004 ). There was a negative association between SAM and glutathione level ( ρ = − 0.343 , p = 0.011 ). Interleukin-6 (IL-6) levels were associated with SAM ( ρ = 0.44 , p = 0.01 ) and SAH ( ρ = 0.534 , p = 0.001 ) levels. Conclusions. A high SAM level and high methylation index are associated with the risk of lung injury in patients with COVID-19. The association of SAM with IL-6 and glutathione indicates an important role of transmethylation in the development of cytokine imbalance and oxidative stress in patients with COVID-19.

A rapid and selective method has been developed for highly sensitive determination of total cysteine and homocysteine levels in human blood plasma and urine by capillary electrophoresis (CE) coupled with liquid–liquid extraction. Analytes were first derivatized with 1,1′‐thiocarbonyldiimidazole and then samples were purified by chloroform–ACN extraction. Electrophoretic separation was performed using 0.1 M phosphate with 30 mM triethanolamine, pH 2, containing 25 μM CTAB, 2.5 μM SDS, and 2.5% polyethylene glycol 600. Samples were injected into the capillary (with total length 32 cm and 50 μm id) at 2250 mbar*s and subsequent injection was performed for 30 s with 0.5 M KОН. The total analysis time was less than 9 min, accuracy was 98%, and precision was <2.6%. The LOD was 0.2 μM for homocysteine and 0.5 μM for cysteine. The use of liquid–liquid extraction allowed the precision and sensitivity of the CE method to be significantly increased. The validated method was applied to determine total cysteine and homocysteine content in human blood plasma and urine samples obtained from healthy volunteers and patients with kidney disorders.

A new approach has been developed for the direct determination of reduced (glutathione [GSH]) and oxidized (glutathione disulfide [GSSG]) GSH in whole blood by means of capillary electrophoresis. Its features include GSH‐stabilizing sample preparation, the use of an internal standard, and pH‐mediated stacking. Blood stabilized with acid citrate and K3EDTA was treated with acetonitrile with N‐ethylmaleimide, and then the analytes were extracted with diethyl ether. The total analysis time was 8 min using a 50‐µm (i.d.) by 32.5‐cm (eff. length) silica capillary. The background electrolyte was 0.075‐M citrate Na pH 5.8 with 200‐µM cetyltrimethylammonium bromide and 5‐µM sodium dodecyl sulfate, and the separation voltage was −14 kV. The quantification limit (S/N = 15) of the method was 1.5 µM for GSSG. The accuracy levels of GSH and GSSG analysis were 104% and 103%, respectively, and between‐run precision levels were 2.6% and 3.2%, respectively. Analysis of blood samples from healthy volunteers (N = 24) showed that the levels of GSH and GSSG and the GSH/GSSG ratio in the whole blood were 1.05 ± 0.14 mM, 3.9 ± 1.25 µM, and 256 ± 94, respectively. Thus, the presented approach can be used in clinical and laboratory practice.

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