Fig. 4: Novel apratoxin reference spectra obtained using the nearest neighbor suspect spectral library.

a Apratoxin cluster in a molecular network created from Moorena bouillonii crude extracts. The reference spectral library hits are shown by the blue squares (b). The purple and pink diamond nodes represent matches to the nearest neighbor suspect spectral library, with the purple diamonds matching the MS/MS spectra shown for which structures could be proposed (c). The white nodes are additional MS/MS spectra within the apratoxin molecular family that remained unannotated, even when including the suspect library. b Reference MS/MS spectra and molecular structures of known apratoxins. c MS/MS spectra and structural hypotheses for four novel apratoxin suspects. All four apratoxin suspects were derived from the tropical marine benthic filamentous cyanobacterium Moorena bouillonii, which is known to produce apratoxins (MSV000086109 [https://doi.org/10.25345/C52475]).