Sea anemones of the genus Zoanthus (family Zoanthidae) are commonly found in subtropical or tropical coastal area. These marine invertebrates are usually cultured in aquarium because of its various colors. Z. vietnamensis Pax & Müller, having a pale pink oral disc with black and white tentacles, was collected in north coastal area of Taiwan and identified by its mitochondrial and nuclear sequence-based phylogenies.1 In previous natural product studies, alkaloids, ceramides, steroids, and sphingolipids were regarded as the major components of zoanthid. In our chemical investigation of Z. vietnamensis, four new alkaloids named fomosamines A‒D (1‒4), along with seven known compounds, 7α-hydroxykuroshine A (5), kuroshine A (6), zoanthenamine (7), 3β-hydroxyzoanthenamine (8), 7α-hydroxyzoanthenamine (9), 28-deoxyzoanthenamine (10), and oxyzoanthamine (11) were identified. The structures of all isolated compounds were determined by the interpretation of spectroscopic methods, especially 2D NMR analyses (COSY, HSQC, HMBC, and NOESY). Compound 1 is an oxidized analogue of 28-deoxyzoanthenamine (10) that contains a keto group at the C-11 position. Compound 2 can be characterized as a new kuroshine A type alkaloid with a hemiacetal at C-28. Compounds 3 and 4 are new hydroxy derivatives of kuroshine A (6) and zoanthenamine (7), respectively. All compounds were evaluated by MTT assays for cytotoxicity against MDA-MB-231, A549, HepG2 cancer cell lines.
Keywords: alkaloids; Zoanthus vietnamensis; marine natural products
Reference
[1] Reimer JD, Ono S, Iwama A, Tsukahara J, Maruyama T. Zoolog Sci 2006; 23:755–761.