Abstract
This paper describes a novel combined post-extraction process for obtaining bioactive compounds from the aqueous high molecular weight sulfated polysaccharides (SPs) extracts of the green algae, Ulva lactuca. After extracting the SPs, they were enzymatically hydrolyzed then the hydrolysate (V45) was fractionated into eight different molecular weight fractions (F1–F8) using ion exchange chromatography. Crude SPs together with V45 and (F1–F8) were examined for their carbohydrate, protein, and sulfate contents. In addition, their degree of polymerization (DP) was estimated and they were characterized by Fourier Transform Infrared Spectroscopy (FTIR). Fractions S1, F4, F5, and F8 showed promising antioxidant and antitumor activities in vitro. In particular, the remarkable antitumor activity of F5 on three types of cancer cell lines could be attributed to its comparable contents of protein, carbohydrate, and sulfate, in addition to its comparable contents of rhamnose and glucuronic acid, and the same for glucose and arabinose. F5 also possessed the highest Hill coefficient among the four promising fractions indicating a higher degree of cooperativity in ligand binding. Other influencing factors including DP, composition, and type of characteristic functional groups were also discussed. The implications of this work could potentially benefit the industries of food supplements and pharmaceuticals.
Highlights
In the past decades, marine seaweeds have gained much interest as wealthy resources of bioactive compounds
As a follow up to our previous work where we showed that enzymatic hydrolysis improves the biological activity of crude extracts, we propose for the first time, to the best of our knowledge, a novel combined process of post-extraction hydrolysis followed by ion exchange column fractionation of algal sulfated polysaccharides (SPs)
We investigate the effect of the enzymatic hydrolysis and anion exchange chromatographic purification on the 2,2-diphenyl-1-picrylhydrazyl (DPPH) antioxidant and antitumor activities of the collected mother fraction (S1), the enzymatically-hydrolyzed fraction (V45), and the eight column effluent fractions (F1–F8)
Summary
Marine seaweeds have gained much interest as wealthy resources of bioactive compounds. Sulfated polysaccharides (SPs) extracted from algal species have shown various biological and physiological activities. As commonly known by “sea lettuce”, is an edible green seaweed from which the SPs, ulvans, are extracted. Not all ulvans are water soluble; the insoluble ones resemble cellulose [1]. Their molecular weight ranges from 189 to 8200 KDa and they are composed of units of mono or disaccharides such as rhamnose, xylose, and iduronic or glucuronic acid. The most abundant unit is ulvan biouronic acid with sulfate at C3 where the acid unit could be either glucuronic or iduronic acid [2]
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