Synthesis, structure elucidation, and determination of polyhalogenated N-methylpyrroles (PMPs) in blue mussels

Abstract

Polyhalogenated N-methylpyrroles (PMPs) are halogenated natural products (HNPs) recently detected in seagrass, blue mussels, and other marine organisms. In this study, we synthesized 2,3,4,5-tetrachloro-N-methylpyrrole (Cl-MP), 2,3,4,5-tetrabrominated-N-methylpyrrole (Br-MP, aka TBMP), and mixed tetrahalogenated (Cl and Br) N-methylpyrrole congeners. Use of one- and two-dimensional H andC NMR verified the structures of isolated/enriched 3,4-dibromo-2,5-dichloro-N-methylpyrrole (3,4-Br-2,5-Cl-MP), 2,3,4-tribromo-5-chloro-N-methylpyrrole (2,3,4-Br-5-Cl-MP), and 3-bromo-2,4,5-trichloro-N-methylpyrrole (3-Br-2,4,5-Cl-MP). GC/EI-MS and GC/ECNI-MS mass spectra of the five PMPs were studied with regard to fragmentation pattern and individual responses which were strongly affected by the presence (or absence) of Br in α-position(s). Quantitative solutions of the synthesized standards were used to determine the elution order of isomers and to quantify PMPs in selected blue mussel samples (Mytilus sp.) from the European Atlantic coast (Spain, France), the North Sea (the Netherlands, Germany) and Baltic Sea (Germany). PMPs were detected in all samples and the concentrations ranged between 0.6 and 52 μg/kg lipids with Br-MP being the most abundant representative of this substance class.

Marine natural products

“…637,638 A series of halogenated N-methylpyrroles were synthesised and used as standards to quantify their presence in European Atlantic, North Sea and Baltic Sea specimens of Mytilus sp. 639 Exposure to okadaic acid has been found to reduce the antioxidant and non-specic immune responses of bay scallops Argopecten irradians. 640 Feeding of a dinophysitoxin-producing microalga (Prorocentrum foraminosum) to Gray's mussel (Crenomytilus grayanus) led to accumulation of dinophysitoxin-1 in the digestive gland and gills while dinophysitoxin-3 levels were highest in the digestive gland.…”