Determination of lipoic acid in biological samples

A new chromatographic method for the determination of cysteine, glutathione, homocysteine and Nɛ-homocysteinyllysine isopeptide in human plasma

Cysteine and glutathione can be applied as therapeutic targets in civilization diseases such as diabetes mellitus and cancers. On the other hand, an elevated concentration of homocysteine, and its metabolites such as homocysteine thiolactone and Nɛ-homocysteinyllysine result in health problems and has been indicated as an independent risk factor for cardiovascular disease and accelerated atherosclerosis. This work describes the first simplified HPLC-UV method that allows simultaneous determination of Nɛ-homocysteinyllysine isopeptide, cysteine, glutathione and homocysteine in human plasma. The assay is based on reversed-phase high performance liquid chromatography with UV detection and simultaneous reduction of disulfide bound with tris(2-carboxyethyl)phosphine and the selective pre-column derivatization of the thiol group with 1-benzyl-2-chloropyridinium bromide. Linearities of the detector responses for plasma samples were observed in ranges: 0.1-10.0 nmol/mL for Nɛ-homocysteinyllysine, 2.0-60.0 nmol/mL for glutathione and homocysteine, 20.0-600.0 nmol/mL for cysteine. The proposed method reduces the number of steps, shortens the total time of sample preparation, and limits the amount of single-use polypropylene laboratory materials.

The Influence of UV Varnishes on the Content of Cysteine and Methionine in Women Nail Plates-Chromatographic Studies

The main purpose of this work was to determine if the use of hybrid nail polishes causes changes in concentration of the most important sulfur amino acids that build nail plate structures, cysteine and methionine. We found that the average contents of cysteine and methionine in studied samples before the use of hybrid manicure were 1275.3 ± 145.9 nmol mg⁻¹ and 111.7 ± 23.8 nmol mg⁻¹, respectively. After six months of hybrid manicure use, the average amount of these sulfur amino acids in studied samples were 22.1% and 36.5% lower in the case of cysteine and methionine, respectively. The average amounts of cysteine and methionine in nail plate samples after the use of hybrid manicures were 992.4 ± 96.2 nmol mg⁻¹ and 70.9 ± 14.8 nmol mg⁻¹, respectively. We also confirmed that in studied women the application of UV light varnishes reduced the thickness of the nail plate, from 0.50 ± 0.12 mm before to 0.46 ± 0.12 mm after the use of the hybrid manicure.

Is ferroptosis involved in ROS-induced testicular lesions in a varicocele rat model?

BACKGROUND

Ferroptosis is an iron-dependent cell death that is distinct from apoptosis. Based on excessive amounts of iron and reactive oxygen species in varicocele (VCL) rats, we hypothesize that ferroptosis might be involved in VCL. In addition, since alpha-lipoic acid (ALA) was shown to have both antioxidant and anti-ferroptotic activity we assessed in the present work the status of ferroptosis in our varicocele model and the protective effect of ALA. To this end, 70 male Wistar rats were divided into 7 groups: control, sham and varicocele groups which were initially sacrificed 2 months after the operation to verify the induction of varicocele. A second batch of the same 3 groups were sacrificed 4 months after varicocele induction to evaluate the effect of ALA supplementation. The parameters measured were chromatin integrity (aniline blue and acridine orange staining), lipid peroxidation (BODIPY staining), testicular morphometry and iron content. In addition, redox (GSH and NADPH) and ferroptosis (Nrf2, Slc7a11, P53 and p-Jnk) markers were evaluated at 2 and 4 months post-operation.

RESULT

The alteration of the spermatic parameters made it possible to verify the induction of the varicocele. Iron accumulated well in the testicles during varicocele and decreased significantly following ALA treatment. Ferroptotic molecular markers at the mRNA and protein levels were not significantly altered. ALA supplementation did not alter NADPH values, but increased GSH levels.

CONCLUSION

Despite the increased accumulation of iron in the testes 2 and 4 months after surgical induction of varicocele, molecular evidence did not demonstrate the involvement of ferroptosis. This could be explained by the mosaic nature of the varicocele affecting some seminiferous tubules and not others which could mask variations in molecular markers. In parallel, our study confirms that ALA stimulates the NRF2 pathway.

A Simplified Method for Simultaneous Determination of α-Lipoic Acid and Low-Molecular-Mass Thiols in Human Plasma

α-Lipoic acid, glutathione, cysteine, and cysteinylglycine can be applied as therapeutic agents in civilization diseases such as diabetes mellitus, cardiovascular diseases, and cancers. On the other hand, a higher concentration of homocysteine can result in health problems and has been indicated as an independent risk factor for cardiovascular disease and accelerated atherosclerosis. Here, the first simplified HPLC-UV assay that enables simultaneous determination of α-lipoic acid and low-molecular-mass thiols in plasma, reduces the number of steps, shortens the total time of sample preparation, and limits the amount of single-use polypropylene laboratory materials is described. The assay is based on reversed-phase high performance liquid chromatography with UV detection and simultaneous reduction of disulfide bound with tris(2-carboxyethyl)phosphine and the selective pre-column derivatization of the thiol group with 1-benzyl-2-chloropyridinium bromide. Linearity in the detector responses for plasma samples were observed in ranges: 0.12-5.0 nmol mL^-1 for α-lipoic acid; 2.0-20.0 nmol mL^-1 for glutathione, cysteinylglycine, and homocysteine; and 40.0-400.0 for cysteine. The LODs for α-lipoic acid and low-molecular-mass thiols were 0.08 and 0.12 nmol mL^-1, respectively, while LOQs were 0.12 and 0.16 nmol mL^-1, respectively. The usefulness of the proposed method has been proven by its application to real samples.

Investigation of lipoic acid - 4-methoxybenzyl alcohol reaction and evaluation of its analytical usefulness

The presented work is aimed to synthesize a new UV active derivative of α-lipoic acid (ALA) by its esterification with 4-methoxybenzyl alcohol (4-MBA, anise alcohol). The formation of ester was confirmed by ¹HNMR, FTIR and UV spectroscopy. The analytical usefulness of the obtained compound for quantification of ALA in food items was examined using HPLC-UV and GC-MS systems. It was found that it is possible to assay ALA in the ester form in the concentration ranges: 5·10^-6-1·10^-4 mol L^-1 by HPLC-UV and 1∙10^-7-5∙10^-5 mol L^-1 by GC-MS techniques. The GC-MS procedure was applied for the determination of ALA in the food samples.

The first method for determination of lipoyllysine in human urine after oral lipoic acid supplementation

Aim: The first method on urinary excreted amounts of lipoyllysine (LLys) after lipoic acid (LA) supplementation was developed and validated. The suggested procedure allowed simultaneous determination of LLys and LA. Methodology & results: After the conversion of analytes into their reduced forms with tris(2-carboxyethyl)phosphine and derivatization via thiol group with 1-benzyl-2-chloropyridinium bromide, separation of analytes derivatives was performed on C18 column using a gradient mobile phase consisting of acetic acid and acetonitrile. The calibration curves for LA and LLys were linear (R² > 0.999) in the range of 0.4-12 μM concentration and all validation results were acceptable, according to the US FDA bioanalytical method guidelines. Conclusion: This method was effectively applied for LA and LLys quantification in human urine after oral LA supplementation.

Application of simultaneous separation and derivatization for the determination of α-lipoic acid in urine samples by high-performance liquid chromatography with spectrofluorimetric detection

To help to clarify therapeutic functions of lipoic acid (LA) in biochemical and clinical practice we have elaborated a fast, simple and accurate HPLC method enabling determination of LA in human urine. The proposed analytical approach includes reduction of LA with tris(2-carboxyethyl)phosphine and simultaneous separation and derivatization of the analyte with butylamine and o-phthaldialdehyde followed by spectrofluorimetric detection at λ_ex  = 340 nm and λ_em  = 440 nm. The assay was performed using gradient elution and the mobile phase containing 0.0025 mol L^-1 o-phthaldialdehyde in 0.0025 mol L^-1 NaOH and acetonitrile. Linearity of the detector response for LA was observed in the range of 0.3-8 μmol L^-1 . Limits of detection and quantification for LA in urine samples were 0.02 and 0.03 μmol L^-1 , respectively. The total analysis time, including sample work-up, was <20 min. The analytical procedure was successfully applied to analysis of real urine samples delivered from six healthy volunteers who received a single 100 mg dose of LA.

Production of Bioactive Compounds by Food Associated Galactomyces geotrichum 38, as Determined by Proteome Analysis

Fried cottage cheese is a dairy product, popular in some parts of Poland. Proteomic analysis of a culture of the mold Galactomyces geotrichum 38 isolated from fried cottage cheese was performed using UHPLC/MS. From the proteins identified, we selected those involved in the biosynthesis of bioactive compounds and those useful in industry. In the G. geotrichum 38 culture, the production quantities of vitamin B₂ (224 μg/L), ergosterol (54.63 mg/kg), and trehalose (0.91 g/L) were determined by HPLC. The identified proteins were also used to prepare a hypothetical fatty acid biosynthesis pathway, and the percentage of individual sphingolipids in the culture was determined. Sphingolipids are also bioactive compounds. During culturing of G. geotrichum 38, the percentage of three sphingolipids increased. The last step of the research was to prepare a model of fried cottage cheese. The mold G. geotrichum 38, used in the process of ripening fried cottage cheese, synthesized vitamin B₂ and erogsterol, which influenced the nutritional value of the product.

Nutritional Interventions for Mitochondrial OXPHOS Deficiencies: Mechanisms and Model Systems

Multisystem metabolic disorders caused by defects in oxidative phosphorylation (OXPHOS) are severe, often lethal, conditions. Inborn errors of OXPHOS function are termed primary mitochondrial disorders (PMDs), and the use of nutritional interventions is routine in their supportive management. However, detailed mechanistic understanding and evidence for efficacy and safety of these interventions are limited. Preclinical cellular and animal model systems are important tools to investigate PMD metabolic mechanisms and therapeutic strategies. This review assesses the mechanistic rationale and experimental evidence for nutritional interventions commonly used in PMDs, including micronutrients, metabolic agents, signaling modifiers, and dietary regulation, while highlighting important knowledge gaps and impediments for randomized controlled trials. Cellular and animal model systems that recapitulate mutations and clinical manifestations of specific PMDs are evaluated for their potential in determining pathological mechanisms, elucidating therapeutic health outcomes, and investigating the value of nutritional interventions for mitochondrial disease conditions.

The issue of HPLC determination of endogenous lipoic acid in human plasma

Lipoic acid (LA) is used extensively as a therapeutic agent for the treatment of various diseases. Many methods have been reported for the determination of LA plasma levels and its metabolites after its supplementation, but available information concerning endogenous plasma levels is still scarce. Studies which directly focused on determining the endogenous plasma levels provided highly controversial results, <4.9 nmol/L or 143.7-197.0 nmol/L. The main aim of this study was to verify the levels of free LA in the plasma of 40 individuals (17 women, 23 men). This group was nonsupplemented with LA and met the conditions for incorporation into the blood donors register. We measured the levels of LA using an HPLC method with very sensitive coulometric detection after previous sample preparation including deproteination and solid-phase extraction with a Phenyl cartridge. Our limit of detection was 1.85 nmol/L and was better than the values reported in studies that directly focused on determining the endogenous plasma levels of LA: 2.4 and 4.9 nmol/L respectively. However, the levels of free LA in the plasma of nonsupplemented voluntary blood donors were not detectable in all cases. The presented results of our study show that endogenous concentrations of LA are <1.85 nmol/L.