Isolation and Structural Elucidation of Secondary Metabolites from New Zealand Marine Sponge Aaptos confertus

This study reports on the spectroscopy-guided isolation and structural elucidation of secondary metabolites from the New Zealand marine sponge Aaptos confertus. An extraction of the sponge material, followed by several purification steps, led to the isolation of potential new compounds CJP02 20A, CJP02 20C and CJP02 04CB, a known 2,5-diketopiperzine cyclo(L-Phe-L-Pro), and a previously reported 3-((13-methylhexadecyl)oxy)propane-1,2-diol. Corrections to the ¹H NMR data reported for 3-((13-methylhexadecyl)oxy)propane-1,2-diol were also recorded. The relationship between the oceanic climate where a marine organism habituates and its production of secondary metabolites is discussed. The isolation of a diverse range of compounds, either novel or new to the genus, suggests that organisms originating in temperate climates are similar in value to those from tropical climates, where higher rates of predation (and therefore, selective pressure) are thought to produce superior diversity in their secondary metabolic distribution. In addition to the new compounds isolated, the diketopiperazine described is the first reported molecule of that class from the genus Aaptos. The significance of the isolated compounds is discussed, in the context of drug discovery and development. The potential of the branched-chain mono-glycerol ether 3-((13-methylhexadecyl)oxy)propane-1,2-diol as a lipid biomarker for the genus Aaptos was examined, as this compound has only been reported from species of that genera. In addition, it’s potential as an immunomodulatory drug is discussed, including the significance of the ether linkage in contrast to the more common ester linkage. The isolation of the 2,5-diketopiperazine cyclo(L-Phe-L-Pro) new to the genus was shown to support the potential in diversity of climate and geographical distribution. This class of molecule is generated through the shikimate biosynthetic pathway; a metabolic route used by bacteria, fungi and algae. A proposed symbiotic relationship between the sponge Aaptos confertus and a proximal bacteria, fungi or algae exemplifies the value of New Zealand’s diverse and unique marine organisms