2,3-Seco-2,3-dioxo-lyngbyatoxin A from a Red Sea strain of the marine cyanobacterium Moorea producens

Abstract

Chemical investigation of the organic extract of a Red Sea strain of the cyanobacterium Moorea producens has afforded 2,3-seco-2,3-dioxo-lyngbyatoxin A (1). Five known compounds including lyngbyatoxin A (2), majusculamides A and B (3 and 4), aplysiatoxin (5) and debromoaplysiatoxin (6) were also isolated. Their structures were elucidated by using HR-FAB-MS, 1D and 2D NMR analyses. The compounds were evaluated for antiproliferative activity against HeLa cancer cells. Lyngbyatoxin A (2) showed potent activity, with an IC₅₀ of 9.2 nM, while 5 and 6 displayed modest activity with IC₅₀ values of 13.3 and 3.03 μM, respectively. In contrast, compounds 1, 3 and 4 were inactive, with IC₅₀ values greater than 50 μM. The lack of cytotoxicity for 2,3-seco-2,3-dioxo-lyngbyatoxin A (1) demonstrates that the indole moiety in lyngbyatoxin (2) is essential for its cytotoxicity, and suggests that detoxification of 2 may be carried out by biological oxidation of the indole moiety to yield 1.

Keywords::

• Red Sea cyanobacterium
• Moorea producens
• 2,3-seco-2,3-dioxolyngbyatoxin A
• lyngbyatoxin
• HeLa cells
• antiproliferative activity

Acknowledgements

The authors also gratefully acknowledge the Science and Technology Unit, King Abdulaziz University for technical support. The award from the President's Council Research Excellence (to SLM) is also acknowledged. We are thankful to Lauren Holmgren for her technical assistance.

Additional information

Funding

This project was supported by the NSTIP strategic technologies program in the Kingdom of Saudi Arabia-Project No. (11-BIO1555-03).