Università degli studi di Modena e Reggio Emilia

Despite several publications have dealt with natural products from specific marine invertebrate groups, such as nudibranchs, cnidarians and sponges, describing their structure and biological activity, some groups of organisms remain poorly studied, including marine annelids. Isolation and characterization of chemical substances from polychaetes have just started out. Furthermore, chemical and ecological investigations not always are brought forward together. In this study, the inflammatory compound complanine was detected in the fireworm Hermodice carunculata through spectrometric analyses. An analogue of this molecule was found both in the dorsal chaetae directly involved in defence against predators, in the digestive apparatus and in exposed palatable tissues. These findings support a synergy between the stinging and fragile notochaetae and complanine-related compounds, that needs to be injected through mechanical injury to display its effects.

Eight betaine-derived novel compounds were found in extracts of the Mediterranean stinging fireworm Hermodice carunculata. The identification of their structures relies on 1D and 2D NMR (Fig. 1-3) and HPLC-ESI/HRMS spectra. Two types of terminal ammonium portions A and B and a series of different alkyl chains were identified (Fig. 4a,b). Their matching provides the structures of uncharacterized secondary metabolites, named carunculines, and their related isomers. These molecules differ from already known trimethylammonium inflammatory compounds (i.e. complanines) isolated from another amphinomid species, for the structures of the terminal ammonium groups (Fig. 4c) [1]. Carunculine anatomical distribution within H. carunculata was assessed by screening through HPLC-ESI/HRMS (Fig. 5, Table 1): their occurrence was revealed in all the body parts analyzed, both involved in predator-prey interactions [2], and mainly in the digestive apparatus. The results achieved reveal an array of different novel compounds from a chemically unknown species, improving knowledge on Marine Animal Products with chemical and biological potential for bioprospection [3]. Overall, these data reinforce the necessity of studying poorly-investigated taxa to expand knowledge on animal venom biology, their mechanisms of action and exploitation as promising source of drug molecules

Increasing evidence in the field of bioprospection fosters the necessity of studying poorly investigated poisonous marine invertebrates to expand knowledge on animal venom biology. Among marine annelids, amphinomid fireworms are notorious for their bearded trunk equipped with a powerful stinging capacity. Here, a methodological workflow based on analytical chemistry techniques (compound isolation followed by mass spectrometry and spectroscopy analyses) was applied to gain new insights, leading to the identification and structural elucidation of an array of natural products from Mediterranean specimens of Hermodice carunculata. Eight betaine-derived unprecedented compounds, named "carunculines", were detected, bearing two terminal ammonium groups tri-and disubstituted at the Cα (A, B) and a series of different alkyl chains (I-VIII). The mixture of chemicals was found in all the body parts of H. carunculata, supporting a mechanism of action triggered by their vehiculation inside the dorsal chaetae, and subsequent injection when chaetae break off on contact. Preliminary investigations to understand adaptive features were also performed, showing a trend in carunculine abundance that fits into the evolutionary history of these worms. These findings shed light on the chemical ecology of amphinomids, giving reasons for the success of H. carunculata in benthic environments and providing promising novel metabolites for biotechnological implications.