Analysis of Reaction betweenα-Lipoic Acid and 2-Chloro-1-methylquinolinium Tetrafluoroborate Used as a Precolumn Derivatization Technique in Chromatographic Determination ofα-Lipoic Acid

Abstract

The present study offers results of analysis concerning the course of reaction between reduced α-lipoic acid (LA) and 2-chloro-1-methylquinolinium tetrafluoroborate (CMQT). In water environments, the reaction between CMQT and hydrophilic thiols proceeds very rapidly and the resultant products are stable. For the described analysis, optimum reaction conditions, such as concentration of the reducing agent, environment pH, and concentration of the reagent were carefully selected. The spectrophotometric assay was carried out measuring absorbance at λ = 348 nm (i.e., the spectral band of the obtained reaction product). Furthermore, the calibration curve of lipoic acid was registered. It was concluded that the Lambert-Beer law was observed within the range 1–10 μmol L−1. Later, the reaction between LA and CMQT was used as precolumn derivatization in a chromatographic determination of the lipoic acid in the range 2.5–50 μmol L−1. Practical applicability of the designed methods was evaluated by determining lipoic acid in Revitanerv pharmaceutical preparation which contains 300 mg LA in a single capsule. The error of the determination did not exceed 0.5% in relation to the declared value.

Development of Novel Silica-Based Formulation of α-Lipoic Acid: Evaluation of Photo and Thermal Stability of the Encapsulated Drug

“…This may be due to the rupture of the disulfide bond of 1,2-dithiolane ring in LA molecules and formation of dihydrolipoic acid (DHLA) [14][15][16]. According to literature data, DHLA shows the absorption band at 200 nm [49].…”

Molecular “wiring” of plasma amine oxidase: Green and enzyme friendly approaches

“…It was reported as a metal chelator and a chemopreventive agent as well [23]. We correlate the increase in LA uptake in the presence of PLP with the formation of an adduct between PLP and the reduced form of LA [24]. FAD was used in the preliminary study, to test the concept of "wiring" PAO through different routes since we used it successfully to modify two other redox enzymes (both flavoproteins).…”

Least median of squares and iteratively re‐weighted least squares as robust linear regression methods for fluorimetric determination of α‐lipoic acid in capsules in ideal and non‐ideal cases of linearity

“…The analysis methods in the BP and USP are the same and a literature search revealed few reported methods for its analysis. HPLC has been used previously to determine LA in biological fluids by either electrochemical detection or two precolumn derivatization methods followed by UV and fluorescence detection . However, few direct spectrophotometric methods have been reported for LA determination, whereas a gas chromatography/mass spectrometry (GC/MS) method has been reported for LA quantitation …”