Abstract
A crude methanolic extract of the Indonesian sponge Clathria bulbotoxa showed a potent cytotoxic activity against the human epidermoid carcinoma A431 cells. An investigation of the active components led to the isolation of three new compounds named crambescidins 345 (1), 361 (2), and 373 (3), together with the known related metabolites crambescidins 359 (4), 657 (5), and 800 (6). The structures of the compounds were determined by spectroscopic analysis. These compounds 1–4 that possess a simple pentacyclic guanidine core exhibited moderate cytotoxicity against the A431 cells with the IC50 values of 7.0, 2.5, 0.94, and 3.1 μM, respectively, while the known compounds 5 and 6 that possess a long aliphatic side chain were found to be significantly cytotoxic. On the other hand, in an anti-oomycete activity test against the fungus-like plant pathogen Phytophthora capsici, 1–4 showed a higher activity than that of 5 and 6, suggesting that the long aliphatic side chain plays a significant role for cytotoxicity, but is not effective or suppressive for anti-oomycete activity.
Highlights
Marine sponges are one of the most prolific and the largest sources of novel bioactive compounds among marine organisms [1,2], with more than 200 new compounds reported each year [3]
The active extract was subjected to Phytophthora bioassay-guided fractionation, followed byThe theactive final extract was subjected to bioassay-guided fractionation, followed the final reversed-phase reversed-phase high performance liquid chromatography (HPLC) by to yield six compounds
Previous structure-activity relationship (SAR) studies on the crambescidins and their analogs reported that the presence of the long aliphatic side chain enhanced the cytotoxic effect of the guanidine core [50,51,52,53]
Summary
Marine sponges (phyla Porifera) are one of the most prolific and the largest sources of novel bioactive compounds among marine organisms [1,2], with more than 200 new compounds reported each year [3]. The sponges of the genus Clathria inhemisphere the tropical [13,14] This genus been recognized as an excellent producer of novel secondary metabolites shallow waters and has temperate regions, especially along the cost of the southern hemisphere [13,14]. Exhibiting diverse chemical structures including alkaloids [15,16,17,18,19,20], carotenoids [21,22], peptides [23], This genus has been recognized as an excellent producer of novel secondary metabolites exhibiting sugars [24], terpenoids [25,26], and sterols [27,28,29].
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