Isolation and synthesis of acmellonate, a new unsaturated long chain 2-ketol ester from Spilanthes acmella.

Paracress (Spilanthes acmella) is commonly used as a spice, e.g., in Madagascar. To get more information about the taste active compounds, Jambu oleoresin produced from Spilanthes acmella and extracts prepared directly from the plant were fractionated and the fractions were analysed and evaluated by tasting. In addition to the long known tingling compounds (2E,6Z,8E)-deca-2,6,8-trienoic acid N-isobutyl amide (spilanthol) and (2E,6Z,8E)-deca-2,6,8-trienoic acid N-(2-methylbutyl) amide, as a minor constituent also the new 2-ketol ester (7Z,9E)-2-oxo-undeca-7,9-dienyl 3-methylbut-2-enoate (acmellonate) was isolated. The structure of the latter compound was verified by total synthesis of the ketol ester via the reaction of tris(trimethylsilyloxy)ethene and (6Z,8E)-deca-6,8-dienoic acid chloride and subsequent classical esterification. Acmellonate shows a weak tingling and numbing effect on the tongue and contributes only to a small extend to the overall flavour of Jambu.

Protein sequences indicate that turtles branched off from the amniote tree after mammals.

The phylogenetic relationships among the major groups of amniote vertebrates remain a matter of controversy. Various alternatives for the position of the turtles have been proposed, branching off either before or after the mammals. To discover the phylogenetic position of turtles in relation to mammals and birds, we have determined cDNA sequences for the eye lens proteins alpha A- and alpha B-crystallin of the red-eared slider turtle (Trachemys scripta elegans). In addition, databases were searched for turtle protein sequences, for which mammalian, avian, and outgroup orthologs were available. All sequences were analyzed by three phylogenetic tree reconstruction methods (neighbor-joining, maximum parsimony, and maximum likelihood). Including the alpha-crystallins, 7 out of 12 proteins support a sister-group relation of turtles and birds with all 3 methods. For each of the other five proteins no topology was consistently preferred by the three approaches. Analyses of the combined amino acid data (1,695 aligned sites) also give extremely strong evidence that turtles are nearer to birds, indicating that mammals branched off before the divergence between turtles and birds occurred.