Linear diterpenes with anticancer activity from the irish brown alga Bifurcaria bifurcata

Ireland has a coastline of 7,000 km with a habitat rich shoreline. Irish marine flora is particularly very diverse comprising over 500 marine algae (seaweed) species with untapped pharmacological and chemical properties. Bifurcaria bifurcata (order Fucales) is a brown alga found on rocky coasts of the N. E. Atlantic Ocean. It is a well-known source of complex phlorotannins and unique acyclic diterpenoids [1]. In the course of our on-going investigations within the frame of Beaufort Marine Biosdiscovery Research Programme aiming at the identification of novel bioactive metabolites from Irish marine resources [2], we have selected B. bifurcata for in-depth chemical studies due to in vitro anticancer activity of its crude extract against the MDA-MB-231 breast cancer cell line (1.7% cell viability at 100 µg/mL). In this report, we describe the isolation and structural features of a new acyclic diterpenoid acid (1) isolated along with three known linear diterpenes (2-4) by chromatographic techniques including normal and reverse phase flash CC and RP18 HPLC from the chloroform sub-extract of the seaweed. The structure of the new natural product was established by means of extensive 1D and 2D NMR and high resolution MS studies. Compounds 2 and 3 showed strong antiproliferative activity toward MDA-MB-231 tumour cells (1.8% and 2.9% cell viability at 100 µg/mL, respectively).

Acknowledgements: The Beaufort Marine Research Award is carried out under the Sea Change Strategy and the Strategy for Science Technology and Innovation (2006 – 2013), with the support of the Marine Institute, funded under the Marine Research Sub-Programme of the National Development Plan 2007 – 2013.

Keywords: Bifurcaria bifurcata, Seaweed, Linear diterpene, Anticancer

References:

[1] Muñoz, J. et al. (2013) Phytochem. Rev. 12: 407 – 424.

[2] Rae, M. et al. (2013) Phytochem. Rev. 12: 555 – 565.