Aaptolines A and B, Two New Quinoline Alkaloids from the Marine Sponge Aaptos aaptos

Abstract

Two new quinoline alkaloids, aaptolines A and B, were isolated from the marine sponge Aaptos aaptos. Their structures were determined by HR-ESI-MS data, NMR analysis, and X-ray crystallography. Structurally, aaptoline A is characterized as having a quinoline skeleton fused with a 1,4-dioxane motif at the C(7)À C(8) position, whereas aaptoline B possessed an intriguing 1H-pyrrolo[2,3-g]quinoline moiety. The cytotoxic assay of these compounds showed no cytotoxicity towards HepG2, A549, and PC9 cancer cell lines and had IC 50 values greater than 20 μM.

Synthesis of Proposed Structure of Aaptoline B via Transition Metal-Catalyzed Cycloisomerization and Evaluation of Its Neuroprotective Properties in C. Elegans

“…Furthermore, based on preceding literature in which the peaks observed at about 125 and 145 ppm were designated as C-9 and C-10 carbon adjacent to nitrogen atom, respectively [16][17][18], the peak at δ 144.7 was assigned as carbons at C-10. Through two-dimensional NMR analysis, we were also able to assign the 13 C-NMR peak of C-9 (δ 120.8) that could not be assigned in the previous study [4]. Overall, our assignment of 1 seems to be more reasonable compared to the previous report.…”

“…However, the NMR spectra of 1 differed from those reported when using the same deuterated solvent (CDCl 3 ). Significant differences were observed in both the 1 H and 13 C NMR spectra of our synthetic sample compared to those of the isolated product [4]. To precisely confirm the structure of synthetic 1, we employed two-dimensional NMR analysis (700 MHz, CD 3 OD; see the Supplementary Materials).…”

“…Aaptoline B (1) has been reported as a pyrroloquinoline alkaloid isolated from the marine sponge Aaptos aaptos by a Chinese research group [4]. Structurally, as shown in Figure 1, 1 is characterized by a unique 7H-pyrrolo [2,3-h]quinoline skeleton embedded with privileged scaffolds, such as indole and quinoline.…”

New Bioactive Polyacetylenes from the Marine Sponge Petrosia sp.

“…In our continuing research for unique and biologically active natural products from marine sponges, [18–21] chemical investigation of a marine sponge of genus Petrosia resulted in the isolation of three new polyacetylenes with vicinal diol, pellynols P–R ( 1 – 3 ), and one known polyacetylene, pellynol H ( 4 ) ( Figure 1). Herein, the details of isolation, structure elucidation, and cytotoxicity of these polyacetylenes are reported.…”

Synthesis of Proposed Structure of Aaptoline A, a Marine Sponge-Derived 7,8-Dihydroxyquinoline, and Its Neuroprotective Properties in C. elegans

“…Aaptoline A ( 1 ) was originally reported as a natural 7,8-dihydroxyquinoline alkaloid isolated from the marine sponge Aaptos suberitoides by Kudo et al in 2014 [ 8 ]. Notably, a Chinese research group also recently appointed a different 7,8-hydroxyquinoline alkaloid derived from Aaptos aaptos as aaptoline A [ 9 ]. 1 was expected to have therapeutic properties against neurodegenerative diseases, particularly PD, because of the 8-hydroxyquinoline and catecholamine moieties in its chemical structure ( Figure 1 ).…”