A marine-derived strain of Dichotomomyces cejpii produces the new compounds emindole SB beta-mannoside (1) and 27-O-methylasporyzin C (2), as well as the known indoloditerpenes JBIR-03 (3) and emindole SB (4). Indole derivative 1 was found to be a CB2 antagonist, while 2 was identified as the first selective GPR18 antagonist with an indole structure. Compound 4 was found to be a nonselective CB1/CB2 antagonist. The new natural indole derivatives may serve as lead structures for the development of GPR18- and CB receptor-blocking drugs.

SummaryMyxobacteria are famous for their ability to produce most intriguing secondary metabolites. Till recently, only terrestrial myxobacteria were in the focus of research. In this review, however, we discuss marine-derived myxobacteria, which are particularly interesting due to their relatively recent discovery and due to the fact that their very existence was called into question. The to-date-explored members of these halophilic or halotolerant myxobacteria are all grouped into the suborder Nannocystineae. Few of them were chemically investigated revealing around 11 structural types belonging to the polyketide, non-ribosomal peptide, hybrids thereof or terpenoid class of secondary metabolites. A most unusual structural type is represented by salimabromide from Enhygromyxa salina. In silico analyses were carried out on the available genome sequences of four bacterial members of the Nannocystineae, revealing the biosynthetic potential of these bacteria.

Natural products from fungi, especially Ascomycota, play a major role in therapy and drug discovery. Fungal strains originating from marine habitats offer a new avenue for finding unusual molecular skeletons. Here, the marine-derived fungus (strain 749) was found to produce the azaphilonoid compounds acetosellin and 5',6'-dihydroxyacetosellin. The latter is a new natural product. The biosynthesis of these polyketide-type compounds is intriguing, since two polyketide chains are assembled to the final product. Here we performedC labeling studies on solid cultures to prove this hypothesis for acetosellin biosynthesis.

Review: [85 refs.