Determination of Tryptophan Metabolites in Serum and Cerebrospinal Fluid Samples Using Microextraction by Packed Sorbent, Silylation and GC–MS Detection

Abstract

Indole-containing acids—tryptophan metabolites—found in serum and cerebrospinal fluid (CSF) samples of patients with diseases of the central nervous system (CNS) were determined with the use of microextraction by packed sorbent (MEPS) followed by silylation and gas chromatography–mass spectrometry (GC–MS) analysis. MEPS with the following silylation led to the reproducible formation of derivatives with an unsubstituted hydrogen ion in the indole ring, the chromatographic peaks of which are symmetric and can be used for GC–MS analysis without additional derivatization. The recoveries of analytes at the limit of quantitation (LOQ) levels were 40–80% for pooled CSF and 40–60% for serum. The limit of detection (LOD) and LOQ values were 0.2–0.4 and 0.4–0.5 µM, respectively, for both CSF and serum. The precision (the reproducibility, RSD) value of less than 20% and the accuracy (the relative error, RE) value of less than ±20% at the LOQ concentrations meet the Food and Drug Administration (FDA) recommendations. Linear correlations for all analytes were determined over a potentially clinically significant range of concentrations (0.4–10 µM for serum, R2 ≥ 0.9942, and 0.4–7 µM for CSF, R2 ≥ 0.9949). Moreover, MEPS significantly reduced the matrix effect of serum compared to liquid–liquid extraction (LLE), which was revealed in the example of reducing the amount of cholesterol and its relative compounds.

Simultaneous determination of serum tryptophan metabolites in an older Chinese population

“…Changes in TRP metabolism are associated with neurodegenerative disorders among older adults. Pautova et al (2020) used microextraction with a packed sorbent followed by N , O ‐bis(trimethylsilyl)trifluoroacetamide derivatization and developed a GC–MS method for identifying IAA, IPA, and 13 other indolic acids in serum. Their reported LOQ values for IAA and IPA were 70 and 75 ng/ml, respectively, and the total run time was 27 min.…”

Chemical Composition and Antioxidant, Anti-Inflammatory, and Enzyme Inhibitory Activities of an Endemic Species from Southern Algeria: Warionia saharae

“…GC–MS analysis is the most suitable technique to assess plant extracts′ lipophilic profile [ 34 , 35 ]. It requires, in some cases, a derivatization procedure to convert many secondary metabolites to volatile derivatives [ 36 ], and silylation is the most recent derivatization procedure [ 37 , 38 ]. The GC–MS analysis of the hydromethanolic extract of W. saharae allowed the identification of four families of compounds: sugars (214.735 µg/mg), alcohols (128.520 µg/mg), carboxylic acids and esters (124.6 µg/mg), and fatty acids (11.364 µg/mg).…”

Gut Microbiota‐Derived Indole Derivatives Alleviate Neurodegeneration in Aging through Activating GPR30/AMPK/SIRT1 Pathway

“…Gut microbiota metabolized Trp to indole and its derivatives, and further transported into blood to potentially across the bloodbrain barrier to play neuroprotective effects in brain. [44,45] Previous study has reported that the mean concentrations of IAA, IPA, and ILA in serum of healthy adults are 1.3, 1.0, and 0.15 μm, respectively. [11] In this study, we determined the concentrations of IAA and IPA in serum of aging mice by HPLC-MS/MS, the results showed that the levels of IAA and IPA were increased after intervention of IAA or IPA (Table S3).…”