Isolation and Purification of a Neuroprotective Phlorotannin from the Marine Algae Ecklonia maxima by Size Exclusion and High-Speed Counter-Current Chromatography

Phlorotannins are polyphenolic metabolites of marine brown algae that have been shown to possess health-beneficial biological activities. An efficient approach using a combination of high-speed counter-current chromatography (HSCCC) and size exclusion chromatography with a Sephadex LH-20 has been successfully developed for the isolation and purification of a neuroprotective phlorotannin, eckmaxol, from leaves of the marine brown algae, Ecklonia maxima. The phlorotannin of interest, eckmaxol, was isolated with purity >95% by HSCCC using an optimized solvent system composed of n-hexane-ethyl acetate-methanol-water (2:8:3:7, v/v/v/v) after Sephadex LH-20 size exclusion chromatography. This compound was successfully purified in the quantity of 5.2 mg from 0.3 kg of the E. maxima crude organic extract. The structure of eckmaxol was identified and assigned by NMR spectroscopic and mass spectrometric analyses. The purification method developed for eckmaxol will facilitate the further investigation and development of this neuroprotective agent as a drug lead or pharmacological probe. Furthermore, it is suggested that the combination of HSCCC and size exclusion chromatography could be more widely applied for the isolation and purification of phlorotannins from marine algae.