Characterization and mapping of secondary metabolites of Streptomyces sp. from caatinga by desorption electrospray ionization mass spectrometry (DESI-MS).

The discovery of new secondary metabolites is a challenge to biotechnologists due to the emergence of superbugs and drug resistance. Knowledge about biodiversity and the discovery of new microorganisms have become major objectives; thus, new habitats like extreme ecosystems have become places of interest to research. In this context, caatinga is an unexplored biome. The ecosystem caatinga is a rich habitat for thermophilic microbes. Its high temperature and dry climate cause selective microbes to flourish and become established. Actinobacteria (Caat 1-54 genus Streptomyces sp.) isolated from the soil of caatinga was investigated to characterize and map its secondary metabolites by desorption electrospray ionization mass spectrometry imaging (DESI-MSI). With this technique, the production of bioactive metabolites was detected and associated with the different morphological differentiation stages within a typical Streptomyces sp. life cycle. High-resolution mass spectrometry, tandem mass spectrometry, UV-Vis profiling and NMR analysis were also performed to characterize the metabolite ions detected by DESI-MS. A novel compound, which is presumed to be an analogue of the antifungal agent lienomycin, along with the antimicrobial compound lysolipin I were identified in this study to be produced by the bacterium. The potency of these bioactive compounds was further studied by disc diffusion assays and their minimum inhibitory concentrations (MIC) against Bacillus and Penicillium were determined. These bioactive metabolites could be useful to the pharmaceutical industry as candidate compounds, especially given growing concern about increasing resistance to available drugs with the emergence of superbugs. Consequently, the unexplored habitat caatinga affords new possibilities for novel bioactive compound discovery. Graphical Abstract ᅟ.

Correction: Rapid determination of the tumour stroma ratio in squamous cell carcinomas with desorption electrospray ionization mass spectrometry (DESI-MS): a proof-of-concept demonstration.

Correction for 'Rapid determination of the tumour stroma ratio in squamous cell carcinomas with desorption electrospray ionization mass spectrometry (DESI-MS): a proof-of-concept demonstration' by Michael Woolman et al., Analyst, 2017, 142, 3250-3260.

New bioanalytical method for the quantification of (-) - hydroxycitric acid in human plasma using UPLC-MS/MS and its application in a Garcinia cambogia pharmacokinetic study.

A new, rapid, selective and sensitive UPLC-MS/MS method was developed and validated for the quantification of (-) - hydroxycitric acid (HCA) in human plasma, using DL-malic acid-2,3,3-d3 as internal standard (IS) and simple protein precipitation for the sample preparations. HCA is a highly polar compound make challenging its determination in biological fluids. A specific chromatography column Acquity UPLC HSS T3 (100 × 2.1 mm, 1.8 µm), eluted with mobile phase composed of acetonitrile/ammonium hydroxide 0,1 % (15:85, v/v) were applied for the HCA quantification. The bioanalytical method showed high-throughput achieving as fast chromatographic run as 1 min per sample. No matrix effect was observed with excellent mean chromatographic peak areas ratio of 0.98 ± 0.07 and CV% of 7.17 from normal, lipemic and hemolyzed plasma lots. Calibration curves range was linear at 0.05-10 µg/mL, presenting adequate mean correlation coefficient great than 0.99. Excellent intra-assay and inter-assay precision were achieved, ranging from 5.02-12.01 % (CV%) as well as great intra- and inter-assay accuracy from 0.29-9.20 % (RE%). UPLC-MS/MS bioanalytical method was efficiently applied to the HCA pharmacokinetic study analyzing more than 670 plasma samples.