Imidazole Alkaloids and Their Zinc Complexes from the Calcareous Marine Sponge Leucetta chagosensis

Abstract

Five new imidazole derivatives (1-5), together with eight related known alkaloids, were isolated from a calcareous marine sponge, Leucetta chagosensis, collected from the South China Sea. Their structures were fully characterized by spectroscopic methods. Structurally, 1 possesses an unusual skeleton featuring imidazole and oxazolone rings linked via a nitrogen atom, whereas 2 bears an intriguing guanylurea-substituted imidazole ring. Compounds 4 and 5 were identified as zinc complexes; they represent the metal complex analogues of naamidine J (6) and pyronaamidine (7), respectively. Among the isolated compounds, 2 and 5 showed significant inhibitory activities toward the LPS-induced production of IL-6 in the human acute monocytic leukemia cell line THP-1, and 7 displayed cytotoxicity against MCF-7, PC9, A549, and breast cancer stem cells (MCF-7-Oct4-GFP) with IC values of 5.2, 5.6, 7.8, and 10 μM, respectively.

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

“…The cytotoxic activities of the new compounds towards three cancer cell lines, HepG2, A549, and PC9 were evaluated by using the previously established CCK‐8 method …”

“…In the course of discovering of structurally diverse metabolites from marine sponges and sponge‐associated microbes, a sample of A. aaptos was re‐collected and subjected to chromatographic purification and two new quinoline alkaloids, aaptolines A ( 1 ) and B ( 2 ) ( Figure ), were isolated and identified. Herein, we report their structural elucidation and biological evaluation.…”

Solvolysis Artifacts: Leucettazoles as Cryptic Macrocyclic Alkaloid Dimers from a Southern Australian Marine Sponge, Leucetta sp.

“…Monomeric 2-aminoimidazoles recovered from Leucetta spp. are attributed a range of biological activities including mammalian cytotoxicity [22] and leukotriene B4 (LTB4) receptor antagonism with possible anti-inflammatory potential [23], and inspired synthetic analogs (i.e., leucettines) that exhibit selective kinase inhibitory activity with potential application against Alzheimer’s disease and Down syndrome [24]. In our hands, the leucettazoles A1 ( 1a ) and B1 ( 2a ) did not exhibit growth inhibitory activity (i.e., half maximal inhibitory concentration (IC 50 ) > 30 μM) against the Gram-negative bacteria Escherichia coli American Type Culture Collection (ATCC) 25922 and Pseudomonas aeruginosa ATCC 10145, the Gram-positive bacteria Staphylococcus aureus ATCC 25923 and Bacillus subtilis ATCC 6633, the fungus Candida albicans ATCC 10231, on human colorectal (SW620) or embryonic kidney (HEK293) carcinoma cells.…”

Efficient Total Synthesis of Lissodendrin B, 2-Aminoimidazole Marine Alkaloids Isolated from Lissodendoryx (Acanthodoryx) fibrosa

“…Therefore, efficient chemical synthesis of marine alkaloids in greater quantities is necessary for their usage in bioactivity studies. 2-aminoimidazole alkaloids, the most commonly investigated representative marine alkaloid, are found primarily in calcareous sponges, especially in the genera Leucetta and Clathrina [2][3][4][5]. These compounds have been extensively studied because of their various biological activities, including anticancer [3][4][5], antimicrobial [2,6], antivirus properties [7,8], P-gp-mediated MDR reversal activity [9] as well as leukotriene B4 receptor [10] and epidermal growth factor (EGF) receptor antagonist activities [11].…”