Abstract
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.
Highlights
Phlorotannins are the major phloroglucinol-derived polyphenols of wide occurrence among marine brown algae, and these have been extensively investigated for various biological activities such as antioxidant, anticancer, anti-inflammatory, anti-allergic, antidiabetic, antihypertensive, and neuroprotective effects [1,2,3,4]
Due to the large amounts of pigments and other unknown polyphenols contained in the crude ethanolic extract of E. maxima, it is difficult to separate and isolate 1 with high purity by high-speed counter-current chromatography (HSCCC) in ethanolic extract of E. maxima, it is difficult to separate and isolate 1 with high purity by HSCCC in one step
An efficient method relying on HSCCC after size exclusion chromatography on Sephadex LH-20 was used to preparative separation of eckmaxol (1) from the leaves of E. maxima in a lossless two chromatic step procedure
Summary
Phlorotannins are the major phloroglucinol-derived polyphenols of wide occurrence among marine brown algae, and these have been extensively investigated for various biological activities such as antioxidant, anticancer, anti-inflammatory, anti-allergic, antidiabetic, antihypertensive, and neuroprotective effects [1,2,3,4]. The leaves of E. maxima are frequently used as source materials for producing alginate, animal feed, nutritional supplements, fertilizers, and for preparation of different medications, including alpha-glucosidase inhibitors applied for the treatment of diabetes mellitus [5,6]. Eckmaxol (1; Figure 1) is a recently reported phlorotannin obtained from the ethyl acetate extract of E. maxima as described in our previous study. This phlorotannin possesses many beneficial properties, including protection against Aβ oligomer induced neurotoxicity in SH-SY5Y cells in vitro [7]. Additional material is required to further investigate the functions of 1 in mammalian systems for the development of this compound as a new pharmacological probe or potential drug lead for treating Alzheimer’s disease
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