A solid-phase microextraction gas chromatography-mass spectrometry technique for urinary metabolomics of human samples infected with schistosomiasis-Case of the Okavango Delta, Botswana

We present a GC-MS metabolomics workflow for analyzing metabolites in urine samples infected with schistosomiasis. Schistosomiasis, a neglected tropical disease, affects 85% of the global population, with the majority residing in Sub-Saharan Africa. The workflow utilized in this study involved the utilization of the AMDIS freeware, Metab R for pre-processing, and multivariate statistical classification through partial least squares-discriminant analysis (PLS-DA). This classification aimed to categorize volatile metabolites found in urine samples from humans infected with schistosomiasis. All samples were collected from individuals in Botswana. A solid-phase microextraction-fused silica fiber was used to adsorb volatile metabolites from the urine samples and inserted into the GC-MS injection port for data acquisition. The acquired data were then subjected to AMDIS auto-deconvolution, Metab R pre-processing, and statistical evaluation for metabolite mining. A total of 12 metabolites, including 3-chloropropionic acid and heptadecyl ester with an AMDIS match factor of 96% at an approximated amount of 0.35% and cyclohexylamine with an AMDIS match factor of 100% and approximated amount of 0.39%, were identified. PLS-DA was used for the classification of the metabolites. The method showed good sensitivity and specificity as indicated by the receiver operating characteristic measured by the areas under the curves. Results indicated that metabolomics is a useful tool for mining metabolites because of the variance in metabolite composition of infected and non-infected urine samples.

Untargeted GC-MS metabolomics to identify and classify bioactive compounds in Combretum platypetalum subsp. oatesii (Rolfe) Exell (Combretaceae)

INTRODUCTION

Combretum platypetalum is used in traditional African healing practices against different infections. Unfortunately, no scientific knowledge of its phytochemical composition exists, except for the isolation of two compounds from the leaves. Scientific study has been limited to the leaves only, despite the applications of stems and roots in traditional medicine practice and natural product drug discovery programs.

OBJECTIVE

Omics was applied to identify and classify different volatile and semivolatile bioactive compounds in the leaf, stem, and root parts of C. platypetalum. The thermal stability of the plant constituents at 60-65°C extraction temperature by Soxhlet and maceration at room temperature on the type, class, and concentration of compounds in the leaf was further investigated.

METHOD

A GC-MS untargeted metabolomics approach, automated deconvolution by the Automated Mass Spectral Deconvolution and Identification System (AMDIS) for GC-MS data, preprocessing by Metab R, and multivariate statistical data analysis were employed in this study.

RESULTS

A total of 97 phytoconstituents, including 17 bioactive compounds belonging to the terpenoids, flavonoids, long-chain fatty acids, and other unclassified structural arrangements distributed across C. platypetalum, were identified for the first time. A correlation (r = 0.782; P = 0.000) between Soxhlet and maceration extraction methods relative to resolved chromatographic peak areas of metabolites was established.

CONCLUSION

Findings corroborate the reported bio-investigation of its leaf extracts, its traditional uses, and previous findings from the Combretum genus. The results substantiate the possible applications of C. platypetalum in natural product drug discovery and provide a guide for future investigations.

Mass spectrometry based metabolomics for small molecule metabolites mining and confirmation as potential biomarkers for schistosomiasis - case of the Okavango Delta communities in Botswana

INTRODUCTION

Metabolomics for identifying schistosomiasis biomarkers in noninvasive samples at various infection stages is being actively explored. The literature on the traditional detection of schistosomiasis in human specimens is well documented. However, state-of-the-art technologies based on mass spectrometry have simplified the use of biomarkers for diagnostics. This review examines methods currently in use for the metabolomics of small molecules using separation science and mass spectrometry.

AREA COVERED

This article highlights the evolution of traditional diagnostic methods for schistosomiasis based on inter alia microscopy, immunology, and polymerase chain reaction. An exhaustive literature search of metabolite mining, focusing on separation science and mass spectrometry, is presented. A comparative analysis of mass spectrometry methods was undertaken, including a projection for the future.

EXPERT COMMENTARY

Mass spectrometry metabolomics for schistosomiasis will lead to biomarker discovery for noninvasive human samples. These biomarkers, together with those from other neglected tropical diseases, such as malaria and sleeping sickness, could be incorporated as arrays on a single biosensor chip and inserted into smartphones, in order to improve surveillance, monitoring, and management.

Comparison of Soxhlet and reflux techniques for extraction and characterisation of potential endocrine-disrupting compounds from solid waste dumpsite soil

Landfill leachate contains a myriad of hazardous chemicals; as such, they should always be planned and constructed following approved guidelines. A sample of soil collected from the old quarry designated as the official solid waste disposal site in Maseru, the capital city of Lesotho, was exposed to two extraction techniques, namely Soxhlet and reflux extractions, for characterisation of the potential endocrine-disrupting chemicals in the leachate. Principal component analysis was used to compare the extractability of these chemicals between the two methods, and it revealed that phthalates extract better in Soxhlet than in reflux extraction. Other compounds do not show as much difference. Qualitative analysis of the extracts revealed several compounds of environmental health interest, namely anthracene, bis-di-ethylhexyl-phthalates and di-tert-butylphenol. A review of the literature on some of the annotated compounds was explored for the likely sources thereof. It was discovered that most of the compounds that were identified have plastic origins and are listed as potential endocrine disruptors. The identified compounds were similar to those reported elsewhere in the literature.

Gas chromatography − mass spectral characteristics of six pharmacologically active compounds — analytical performance characteristics on a raw sewage impacted water sample

We have interrogated the characteristics of six pharmacologically active compounds in a hot gas chromatograph injector including some mass spectral characteristics in a quadrupole mass analyzer. The analytes are dimetridazole, metronidazole, chlorpromazine, trimethoprim, sulfamethazine, and dapsone. We have demonstrated the impact of the injector on the conversion efficiency of solvent to vapor in relation to analytes under investigation. The overall analytical performance of key parameters that were scrutinized and tested on a spiked raw sewer water sample using electron ionization (EI), positive chemical ionization (PCI), and negative chemical ionization (NCI) in the full and selected ion monitoring (SIM) scan modes are also presented. These parameters were the instrument detection limits (IDLs), method detection limits (MDLs), linearities, and percent recoveries. Correlation coefficients (R2) were greater than 0.9950 using all ionization and scan modes. Better MDLs were obtained using the SIM mode in all instances. The SIM mode MDLs ranged as follows: EI 0.308–0.711 and PCI 0.656–1.14 mg/L. Extremely good signals were observed in the NCI mode with dimetridazole and metronidazole where MDLs in the SIM mode were estimated to be 0.057 and 0.062 mg/L. Percent relative standard deviations (n = 3) were all less than 5% using EI employing full and SIM scan modes. Recoveries ranged from 55% to 96% in the full scan mode and from 67% to 94% in the SIM mode. Signal losses and ion population ratios in relation to the number of samples, i.e., scan speed and the mass scan range, are also interrogated.

Pre-electrospray ionisation manifold methylation and post-electrospray ionisation manifold cleavage/ion cluster formation observed during electrospray ionisation of chloramphenicol in solutions of methanol and acetonitrile for liquid chromatography-mass spectrometry employing a commercial quadrupole ion trap mass analyser

We have observed unusual mass spectra of chloramphenicol (CAP) in solutions of methanol or acetonitrile showing intense ions at m/z 297, m/z 311, m/z 325 and m/z 339. The observed ions were different from those which are traditionally observed in the full scan ESI mass spectra of CAP with ions of m/z 321, m/z 323 and m/z 325. We have evidence to show that this process starts with offline methylation of CAP in solutions of methanol or acetonitrile to give m/z 339. Investigations using nuclear magnetic resonance (NMR) spectroscopy showed that there is a methylene group somewhere within the CAP molecule but not attached to any of the carbon atoms when the CAP is dissolved in methanol or acetonitrile before infusion into the mass spectrometer. The possible locations of attachment were speculated to be the electronegative atoms apart from the chlorine atoms due to valence considerations. The methylene group is attached to the nitrogen atom and forms a bond as observed in the MS/MS spectra of m/z 297, m/z 311, m/z 325 and m/z 339 which give m/z 183 as the base peak in all cases. Further experiments showed that there is cleavage of the methylated CAP molecule followed by cluster ion formation involving addition of methylene groups to the CAP fragment with m/z 183 to produce ions of m/z including m/z 297, m/z 311, m/z 325 and m/z 339. This process occurs in the mass spectrometer in the region housing the tube lens and is triggered when the ions are accelerated through this region by application of a negative tube lens offset voltage. This region affords collision of the charged droplets with a collision gas in this case nitrogen to strip the droplets of their solvent molecules. Experiments to follow the intensities of m/z 183, m/z 311, m/z 321, m/z 323, m/z 325 and m/z 339 as the tube lens offset voltage was varied were done in which the intensities of m/z 311, m/z 325 and m/z 339 were observed to be at their peak when the tube lens offset voltage was set at -40 V. When the tube lens offset voltage is swung to +40 V, thus decelerating the ions through the capillary skimmer region via the tube lens, the traditionally observed spectra with m/z 321, m/z 323 and m/z 325 were observed.