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Abstract

Chemical communication in nematodes, such as the model organism Caenorhabditis elegans, is modulated by a variety of glycosides based on the dideoxysugar L-ascarylose. Comparative ascaroside profiling of nematode exometabolome extracts using a GC-EIMS screen reveals that several basic components including ascr#1 (asc-C7), ascr#2 (asc-C6-MK), ascr#3 (asc- DC9), ascr#5 (asc-ωC3), and ascr#10 (asc-C9) are highly conserved among the Caenorhabditis. Three novel, side chain hydroxylated ascaroside derivatives were exclusively detected in the distantly related C. nigoni and C. afra. Molecular structures of these speciesspecific, putative signaling molecules were elucidated by NMR spectroscopy and confirmed by total synthesis and chemical correlations. Biological activities were evaluated using attraction assays. The identification of (ω)- and (ω – 2)-hydroxyacyl ascarosides demonstrates how GC-EIMS-based ascaroside profiling facilitates the detection of novel ascaroside components and exemplifies how species-specific hydroxylation of ascaroside aglycones downstream of peroxisomal β-oxidation increases the structural diversity of this highly conserved class of nematode signaling molecules.