Chemical profiling and rare brominated Aplysinopsins in invasive Tubastraea spp. from the southwestern Atlantic

The sun corals Tubastraea coccinea and T. tagusensis are among the most prolific invasive species in the Southwestern Atlantic. Their adaptability has been associated with a specialized chemical repertoire, yet detailed chemical profiling of these invasive populations remains scarce. In this study, we employed high-resolution LC-MS/MS and 1D/2D NMR (600 MHz) to characterize the secondary metabolism of Tubastraea spp. collected along the Brazilian coast. Our analytical approach led to the annotation of 23 alkaloids, primarily brominated aplysinopsins and rare dimeric derivatives. Among these, six compounds were unequivocally identified by NMR, including isoplysin A and a 6-bromo-2′,4′-dimethyl-1′,8-dihydroaplysinopsin analogue. The chemical profile of T. tagusensis exhibited a distinct metabolic diversity compared to T. coccinea , which coincides with the higher Relative Abundance Index (RAI) observed for this species in monitoring studies. While these brominated alkaloids are potential candidates for allelochemical functions, our findings highlight a high degree of chemical plasticity in invasive populations. This study establishes a molecular baseline for Tubastraea and underscores the importance of integrating chemical markers into the study of invasive marine holobionts.