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. 2019 Jun 5;24(11):2132.
doi: 10.3390/molecules24112132.

Production of Bioactive Compounds from the Sulfated Polysaccharides Extracts of Ulva lactuca: Post-Extraction Enzymatic Hydrolysis Followed by Ion-Exchange Chromatographic Fractionation

Nihal Abou El Azm  1 , Daisy Fleita  2 , Dalia Rifaat  3 , Eric Zadok Mpingirika  4 , Asma Amleh  5 , Mayyada M H El-Sayed  6
Affiliations

Production of Bioactive Compounds from the Sulfated Polysaccharides Extracts of Ulva lactuca: Post-Extraction Enzymatic Hydrolysis Followed by Ion-Exchange Chromatographic Fractionation

Nihal Abou El Azm et al. Molecules. .

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.

Keywords: algae; antioxidant; antitumor activity; enzymatic hydrolysis; ion exchange chromatography; polysaccharides.

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Conflict of interest statement

The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Figures

Figure 1
Figure 1
Illustration of the framework of this study.
Figure 2
Figure 2
(A) Antioxidant activities of the column effluent fractions at different concentrations, along with those of the mother S1 extract and the enzymatically hydrolyzed extract V45. The figure inset shows the activity of ascorbic acid at different concentrations. Sets with the same letters have insignificantly different values at p = 0.05. (B) Relevant IC50 values.
Figure 3
Figure 3
Dose–response curves for fractions S1 on HCT116 cells (A), F4 on HePG2 cells (B), F5 on HePG2 cells (C), F5 on A549 cells (D), and F5 and F8 on MCF7 cells (E). The dose–response curves were used to determine LC50, LC90, and Hill coefficient values.
Figure 4
Figure 4
Evolution of % lethality with concentration for (A) S1 fraction on HCT116 colon cancer cells, (B) F8 fraction on MCF7 breast cancer cells, (C) F4 fraction on HePG2 human hepatocellular carcinoma cells, and (D) F5 fraction on A549, HePG2, and MCF7 cells. The linear parts of the curves are shown in the figure insets.
Figure 5
Figure 5
Hill coefficients for fractions that showed lethality ≥75%. The least Hill coefficient obtained was that of fraction F4 when tested on HepG2 cells while the greatest Hill coefficient was that of fraction F5 when tested on HePG2 cells. Fraction F5 showed significantly higher Hill coefficients (*** p < 0.001) when tested on both HePG2 and A549 cells than on MCF7 cells.
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