Phytotoxic Arylethylamides from Limnic Bacteria Using a Screening with Microalgae.

N-Phenylethylamides 1a-1f, were isolated from cultures of three limnic strains GW90a, GW102a and GW73a.Strain GW102a delivered additionally the compound cyclo (isoleucyldehydroalanyl) (2).The structure of these compounds were assigned by a detailed spectral analysis.Due to their potential use as herbicides, various related compounds 1a, 3, 4a and 4b were synthesized.The minimum inhibitory concentration (MIC) against Chlorella vulgaris, Chlorella sorokiniana, Chlorella salina and Scenedesmus subspicatus ranged from 100 to 12.5μg/ml.All these amides were found to be inactive against Mucor miehei, Candida albicans, and some bacteria.Aquatic microorganisms are a rich source of new and biomedically relevant constituents1).We have focussed our efforts to explore the potential of biologically active marine and limnic bacterial extracts for antimicroalgal, antibacterial and antifungal activity2).In the course of this screening, extracts of the limnic strains GW90a, GW 102a and GW73a were shown to possess potent antimicroalgal activity.Fermentation of strain GW90a and separation of the extract afforded four new N-phenylethylamides 1b-1e.From the strain GW102a in addition to the metabolites above, the new compounds 2-methyl-N-(2'-phenylethyl)butyramide (1f) and cyclo (isoleucyldehydroalanyl) (2) were isolated, while another limnic strain GW73a delivered the arylethylamide 1d.Due to their expected biological properties, arylethylamides 1a and 3 as well as their analogues 4a and 4b were synthesized.This paper deals with the taxonomic characterisation of the producing organisms, the production, isolation and synthesis of arylethylamides and analogues, and describes their antimicroalgal activity.