https://pubs.rsc.org/en/content/articlepdf/2019/NP/C8NP00092A

Marine natural products.

Fatty acids have been used as qualitative markers to trace or confirm predator-prey relationships in the marine environment for more than thirty years. More recently, they have also been used to identify key processes impacting the dynamics of some of the world's major ecosystems. The fatty acid trophic marker (FATM) concept is based on the observation that marine primary producers lay down certain fatty acid patterns that may be transferred conservatively to, and hence can be recognized in, primary consumers. To identify these fatty acid patterns the literature was surveyed and a partial least squares (PLS) regression analysis of the data was performed, validating the specificity of particular microalgal FATM. Microalgal group specific FATM have been traced in various primary consumers, particularly in herbivorous calanoid copepods, which accumulate large lipid reserves, and which dominate the zooplankton biomass in high latitude ecosystems. At higher trophic levels these markers of herbivory are obscured as the degree of carnivory increases, and as the fatty acids originate from a variety of dietary sources. Such differences are highlighted in a PLS regression analysis of fatty acid and fatty alcohol compositional data (the components of wax esters accumulated by many marine organisms) of key Arctic and Antarctic herbivorous, omnivorous and carnivorous copepod species. The analysis emphasizes how calanoid copepods separate from other copepods not only by their content of microalgal group specific FATM, but also by their large content of long-chain monounsaturated fatty acids and alcohols. These monounsaturates have been used to trace and resolve food web relationships in, for example, hyperiid amphipods, euphausiids and fish, which may consume large numbers of calanoid copepods. Results like these are extremely valuable for enabling the discrimination of specific prey species utilized by higher trophic level omnivores and carnivores without the employment of invasive techniques, and thereby for identifying the sources of energetic reserves. A conceptual model of the spatial and temporal dominance of group-specific primary producers, and hence the basic fatty acid patterns available to higher trophic levels is presented. The model is based on stratification, which acts on phytoplankton group dominance through the availability of light and nutrients. It predicts the seasonal and ecosystem specific contribution of diatom and flagellate/microbial loop FATM to food webs as a function of water column stability. Future prospects for the application of FATM in resolving dynamic ecosystem processes are assessed.

Fatty acid trophic markers in the pelagic marine environment.

2,5-Diketopiperazines: synthesis, reactions, medicinal chemistry, and bioactive natural products.

The hydrophobic nature of lipids provides a convenient means of separating them from other compounds in an aqueous sample matrix. Extraction in nonpolar solvents is universally employed and is the basis of the operational definition of lipids. This approach is used routinely in algal biosynthetic studies in which the fate of a radiolabeled precursor is followed into the lipid pool. By adding 14C bicarbonate to a sample from the field (Wainman and Lean, 1992) or a culture (Rai, 1995) and then later extracting the sample with a water-immiscible organic solvent, the “lipid fraction of carbon fixation” (LFCF) can be determined (Wainman and Lean, 1992). By performing a chromatographic separation before counting, this procedure can be further refined to determine the subclasses in which the 4C ends up (Smith and D’ Souza, 1993). Subfractionation is important when a differentiation between allocation to lipid storage and membrane synthesis is required. The radiolabeling approach is convenient, sensitive, and not prone to contamination. However, many ecological studies are not amenable to this approach, and so chemical analysis of the constituents of lipid extracts has to be performed.

Determination of Total Lipid, Lipid Classes, and Fatty Acids in Aquatic Samples

Among the various biochemical markers, fatty acids or lipid profiles represent a chemically relatively inert class of compounds that is easy to isolate from biological material. Fatty acid (FA) profiles are considered as chemotaxonomic markers to define groups of various taxonomic ranks in flowering plants, trees and other embryophytes. The fatty acid profiles of 2076 microalgal strains from the culture collection of algae of Gottingen University (SAG) were determined in the stationary phase. Overall 76 different fatty acids and 10 other lipophilic substances were identified and quantified. The obtained FA profiles were added into a database providing information about fatty acid composition. Using this database we tested whether FA profiles are suitable as chemotaxonomic markers. FA distribution patterns were found to reflect phylogenetic relationships at the level of phyla and classes. In contrast, at lower taxonomic levels, e.g. between closely related species and even among multiple isolates of the same species, FA contents may be rather variable. FA distribution patterns are suitable chemotaxonomic markers to define taxa of higher rank in algae. However, due to their extensive variation at the species level it is difficult to make predictions about the FA profile in a novel isolate.

/pdf/fatty-acid-profiles-and-their-distribution-patterns-in-34h73ynk1i.pdf

Fatty acid profiles and their distribution patterns in microalgae: a comprehensive analysis of more than 2000 strains from the SAG culture collection

Myrrh and opopanax has been used throughout history in incense and as a perfume. Since Bible times it has been used for the treatment of wounds. The first attempts to identify content compounds were almost 100 years ago. In this review we discuss the present state of knowledge in the chemistry of substances of Commiphora spp.

/pdf/myrrh-commiphora-chemistry-57cbmp1udu.pdf

Myrrh--Commiphora chemistry.

Biologically Active Compounds Of Semi-Metals

Diversity of the fatty acids of the Nostoc species and their statistical analysis

Hirtusneanoside, a new O-deoxyglycoside of a dimeric tetrahydroxanthone, was isolated from the lichen Usnea hirta. Its structure, including the absolute configuration, was determined by means of extensive spectroscopic data (UV, IR, MS, CD, 1D and 2D NMR) and chemical degradation. Hirtusneanoside has a unique structure comprising L-rhamnopyranoside of a tetrahydroxanthone dimer and showed growth inhibitory activities against Gram-positive bacteria.

Tomas Rezanka

Papers

Myrrh--Commiphora chemistry.

Biologically Active Compounds Of Semi-Metals

Diversity of the fatty acids of the Nostoc species and their statistical analysis

Hirtusneanoside, an unsymmetrical dimeric tetrahydroxanthone from the lichen Usnea hirta.

Lipid composition of three macrophytes from the Caspian Sea