Palythine–threonine, a major novel mycosporine-like amino acid (MAA) isolated from the hermatypic coral Pocillopora capitata

Using a high-resolution reverse-phase liquid chromatography method we found that the tissues of the hermatypic coral Pocillopora capitata (collected in Santiago Bay, Mexico) contain a high diversity of primary and secondary mycosporine-like amino acids (MAAs) typical of some reef-building coral species: mycosporine–glycine, shinorine, porphyra-334, mycosporine–methylamine–serine, mycosporine–methylamine–threonine, palythine–serine, palythine and one additional novel predominant MAA, with an absorbance maximum of 320 nm. Here we document the isolation and characterization of this novel MAA from the coral P. capitata. Using low multi-stage mass analyses of deuterated and non deuterated compounds, high-resolution mass analyses (Time of Flight, TOF) and other techniques, this novel compound was characterized as palythine–threonine. Palythine–threonine was also present in high concentrations in the corals Pocillopora eydouxi and Stylophora pistillata indicating a wider distribution of this MAA among reef-building corals. From structural considerations we suggest that palythine–threonine is formed by decarboxylation of porphyra-334 followed by demethylation of mycosporine–methylamine–threonine.