Occurrence and fate studies (sunlight exposure and stable carbon isotope analysis) of the halogenated natural product MHC-1 and its producer Plocamium cartilagineum

Naturally Occurring Organohalogen Compounds-A Comprehensive Review

The present volume is the third in a trilogy that documents naturally occurring organohalogen compounds, bringing the total number-from fewer than 25 in 1968-to approximately 8000 compounds to date. Nearly all of these natural products contain chlorine or bromine, with a few containing iodine and, fewer still, fluorine. Produced by ubiquitous marine (algae, sponges, corals, bryozoa, nudibranchs, fungi, bacteria) and terrestrial organisms (plants, fungi, bacteria, insects, higher animals) and universal abiotic processes (volcanos, forest fires, geothermal events), organohalogens pervade the global ecosystem. Newly identified extraterrestrial sources are also documented. In addition to chemical structures, biological activity, biohalogenation, biodegradation, natural function, and future outlook are presented.

Marine natural products

Covering: 2020This review covers the literature published in 2020 for marine natural products (MNPs), with 757 citations (747 for the period January to December 2020) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1407 in 420 papers for 2020), together with the relevant biological activities, source organisms and country of origin. Pertinent reviews, biosynthetic studies, first syntheses, and syntheses that led to the revision of structures or stereochemistries, have been included. A meta analysis of bioactivity data relating to new MNPs reported over the last five years is also presented.

Fast isolation of the environmentally relevant halogenated natural product MHC-1 by means of countercurrent chromatography

Environmentally relevant halogenated natural products (HNPs) are frequently similarly high concentrated in marine biota as major anthropogenic persistent organic pollutants (POPs). The lack of widely available reference standards, however, hampers the in-depth research of several HNPs. For instance, (1R,2S,4R,5R,1'E)-2-bromo-1-bromomethyl-1,4-dichloro-5-(2'-chloroethenyl)-5-methylcyclohexane (MHC-1), which is produced by species referred to the red seaweed Plocamium cartilagineum has not yet been synthesized due to its complex structure and stereochemistry. For this reason, we aimed to establish a method for fast isolation of mg-amounts of MHC-1 from its natural producer based on countercurrent chromatography (CCC). Five biphasic solvent systems were tested and finally, the solvent system acetonitrile/n-hexane/toluene (9:9:2, v/v/v) was selected for the separations due to its suitable partition coefficient of MHC-1 (K_U/L = 0.52). n-Hexane extracts of dried P. cartilagineum were directly injected into the CCC system. Four subsequent CCC runs from three samples of Plocamium cartilagineum (two from Heligoland, Germany and one from Brittany, France) could be performed with high reproducibility. Together, the main fraction provided ~16 mg MHC-1 in a purity of >97% according to GC/FID, GC/ECNI-MS and NMR analysis. This amount could be used to prepare ~1600 quantitative standard solutions of MHC-1. The high MHC-1 content in the seaweed sample collected at Brittany indicated that this area was another hotspot of MHC-1.

Naturally occurring organobromine compounds (OBCs) including polybrominated dibenzo-p-dioxins in the marine sponge Hyrtios proteus from The Bahamas

Halogenated natural products (HNPs) were identified from organic extracts of the marine sponge Hyrtios proteus from The Bahamas using gas chromatography with electron capture negative ion mass spectrometry and non-targeted gas chromatography with electron ionization mass spectrometry. The HNPs found have similar properties to anthropogenic persistent organic pollutants (POPs). Two ortho-methoxy brominated diphenyl ethers (MeO-BDEs) 2'-MeO-BDE 68 and 6-MeO-BDE 47 were the most abundant compounds. Fourteen other MeO-BDEs were detected along with several polybrominated dibenzo-p-dioxins (PBDDs) (1,3,7-triBDD, 1,3,6,8-tetraBDD and 1,3,7,9-tetraBDD) and MeO-PBDDs. Further analysis of a higher trophic level octopus (Octopus maya) from the same FAO fishing area showed that the major HNPs detected in Hyrtios proteus were also predominant. Moreover, HNPs were more than 30-fold higher in abundance than the major POPs in the octopus, i.e., polychlorinated biphenyls. Hence, Caribbean marine organisms, including those potentially used for food, harbor relatively high concentrations of HNPs.

High levels of halogenated natural products in large pelagic fish from the Western Indian Ocean

Concentrations, profiles and muscle-liver distribution of halogenated natural products (HNPs) and anthropogenic persistent organic pollutants (POPs) were investigated in five large pelagic fish species and one smaller planktivore fish species from the Western Indian Ocean. Analysis of swordfish muscle from the Seychelles revealed the predominance of HNPs, with the highest concentrations found for 2'-methoxy-2,3',4,5'- tetraBDE (2'-MeO-BDE 68 or BC-2), 6-methoxy-2,2',4,4'- tetraBDE (6-MeO-BDE 47 or BC-3) and 2,3,3',4,4',5,5'-heptachloro-1'-methyl-1,2'-bipyrrole (Q1), along with varied contributions of further HNPs. The mean concentration of ∑HNPs (330 ng/g lw) was one or two orders of magnitude higher than ∑DDTs (60 ng/g lw) and ∑PCBs (6.8 ng/g lw). HNPs (BC-2, BC-3 and Q1) were also predominant in individual samples of three tropical tuna species from the Seychelles and from other regions of the Western Indian Ocean (Mozambique Channel, off Somalia and Chagos Archipelago). Non-targeted gas chromatography coupled with electron capture negative ion mass spectrometry operated in the selected ion monitoring mode (GC/ECNI-MS-SIM) analysis of one swordfish sample indicated low abundance of rarely reported HNPs (three hexachloro-1'-methyl-1,2'-bipyrrole (Cl₆-MBP) isomers and pentabromo-1,1'-dimethyl-2,2'-bipyrroles (Br₅-DBP)) but no further abundant unscreened polyhalogenated compounds.