UPLC⁻MS/MS Identification of Sterol Sulfates in Marine Diatoms

Cell-Death Metabolites from Cocconeis scutellum var. parva Identified by Integrating Bioactivity-Based Fractionation and Non-Targeted Metabolomic Approaches

Epiphytic diatoms growing in Mediterranean seagrass meadows, particularly those of the genus Cocconeis, are abundant and ecologically significant, even in naturally acidified environments. One intriguing aspect of some benthic diatoms is their production of an unidentified cell-death-promoting compound, which induces destruction of the androgenic gland in Hippolyte inermis Leach, 1816, a shrimp exhibiting protandric hermaphroditism, principally under normal environmental pH levels. The consumption of Cocconeis spp. by this shrimp is vital for maintaining the stability of its natural populations. Although many attempts have been made to reveal the identity of the apoptotic compound, it is still unknown. In this study, we strategically integrated a bioactivity-based fractionation, a metabolomic approach, and two different experimental avenues to identify potential apoptotic metabolites from Cocconeis scutellum var. parva responsible for the sex reversal in H. inermis. Our integrated analysis uncovered two potential candidate metabolites, one putatively identified as a lysophosphatidylglycerol (LPG) (16:1) and the other classified as a fatty acid ester. This is the first time LPG (16:1) has been reported in C. scutellum var. parva and associated with cell-death processes. These candidate metabolites mark substantial progress in elucidating the factors responsible for triggering the removal of the androgenic gland in the early post-larval phases of H. inermis.

Algal blooms in the ocean: hot spots for chemically mediated microbial interactions

The cycling of major nutrients in the ocean is affected by large-scale phytoplankton blooms, which are hot spots of microbial life. Diverse microbial interactions regulate bloom dynamics. At the single-cell level, interactions between microorganisms are mediated by small molecules in the chemical crosstalk that determines the type of interaction, ranging from mutualism to pathogenicity. Algae interact with viruses, bacteria, parasites, grazers and other algae to modulate algal cell fate, and these interactions are dependent on the environmental context. Recent advances in mass spectrometry and single-cell technologies have led to the discovery of a growing number of infochemicals - metabolites that convey information - revealing the ability of algal cells to govern biotic interactions in the ocean. The diversity of infochemicals seems to account for the specificity in cellular response during microbial communication. Given the immense impact of algal blooms on biogeochemical cycles and climate regulation, a major challenge is to elucidate how microscale interactions control the fate of carbon and the recycling of major elements in the ocean. In this Review, we discuss microbial interactions and the role of infochemicals in algal blooms. We further explore factors that can impact microbial interactions and the available tools to decipher them in the natural environment.

Bioactive Molecules from Marine Diatoms and Their Value for the Nutraceutical Industry

The search for novel sources of nutrients is among the basic goals for achievement of sustainable progress. In this context, microalgae are relevant organisms, being rich in high-value compounds and able to grow in open ponds or photobioreactors, thus enabling profitable exploitation of aquatic resources. Microalgae, a huge taxon containing photosynthetic microorganisms living in freshwater, as well as in brackish and marine waters, typically unicellular and eukaryotic, include green algae (Chlorophyceae), red algae (Rhodophyceae), brown algae (Phaeophyceae) and diatoms (Bacillariophyceae). In recent decades, diatoms have been considered the most sustainable sources of nutrients for humans with respect to other microalgae. This review focuses on studies exploring their bio-pharmacological activities when relevant for human disease prevention and/or treatment. In addition, we considered diatoms and their extracts (or purified compounds) when relevant for specific nutraceutical applications.

Phytosterol Profiles, Genomes and Enzymes - An Overview

The remarkable diversity of sterol biosynthetic capacities described in living organisms is enriched at a fast pace by a growing number of sequenced genomes. Whereas analytical chemistry has produced a wealth of sterol profiles of species in diverse taxonomic groups including seed and non-seed plants, algae, phytoplanktonic species and other unicellular eukaryotes, functional assays and validation of candidate genes unveils new enzymes and new pathways besides canonical biosynthetic schemes. An overview of the current landscape of sterol pathways in the tree of life is tentatively assembled in a series of sterolotypes that encompass major groups and provides also peculiar features of sterol profiles in bacteria, fungi, plants, and algae.

Rapid Screening and Quantification of Multi-Class Multi-Residue Veterinary Drugs in Pork by a Modified Quechers Protocol Coupled to UPLC-QOrbitrap HRMS

Background:

A rapid and simple analytical method for the screening and quantification of multi-residues was established by a quick, easy, cheap, effective, rugged and safe (QuEChERS) approach coupled to ultra-performance liquid chromatography and electrospray ionization quadrupole orbitrap high-resolution mass spectrometry (UPLC-Q-Orbitrap HRMS). A total number of 59 veterinary drugs were investigated, which belonged to 12 classes, such as β-agonist, quinolones, sulfonamides, tetracyclines, lincomycin series, triphenylmethane, nitroimidazoles, macrolides, amide alcohols, quinoxalines, steroid hormone and sedatives.

Methods:

The factors which influence the determination of veterinary drugs residues, such as mobile phase, extract solvent, clean up sorbent, and re-dissolved solvent, were optimized by the single factor experiment. The method was sufficiently validated by using the parameters of linearity, sensitivity, accuracy, and repeatability.

Results:

The response of the detector was linear for 59 veterinary drug residues in extensive range (two to three orders of magnitude) with a high coefficient of determination (R2) (0.9995-0.9998). The limit of quantification (LOQ) ranged from 0.1μg/kg to 2.0μg/kg for 59 veterinary drug residues in pork samples. The repeatability was in the range of 1.0%-9.5%. Average recoveries of 59 veterinary drugs at three spiked levels ranged from 53.7%-117.8% with relative standard deviation (RSD) of 1.9%-13.9%. The full MS scan coupled with data-dependent MS/MS mode was applied for screening the target compounds to simultaneously obtain the accurate mass of parent ion and the mass spectrum of fragments. Elemental composition, accurate mass, and retention time and characteristic fragment ions were used to establish a homemade database.

Conclusion:

The ability of the homemade database was verified by analyzing the real pork samples, and the result was satisfactory.

Sulfur-Containing Carotenoids from A Marine Coral Symbiont Erythrobacter flavus Strain KJ5

Erythrobacter flavus strain KJ5 (formerly called Erythrobacter sp. strain KJ5) is a yellowish marine bacterium that was isolated from a hard coral Acropora nasuta in the Karimunjawa Islands, Indonesia. The complete genome sequence of the bacterium has been reported recently. In this study, we examined the carotenoid composition of this bacterium using high-performance liquid chromatography coupled with ESI-MS/MS. We found that the bacterium produced sulfur-containing carotenoids, i.e., caloxanthin sulfate and nostoxanthin sulfate, as the most abundant carotenoids. A new carotenoid zeaxanthin sulfate was detected based on its ESI-MS/MS spectrum. The unique presence of sulfated carotenoids found among the currently known species of the Erythrobacter genus were discussed.