Antibacterial Properties of Fucoidans from the Brown Algae Fucus vesiculosus L. of the Barents Sea.

Olga N Ayrapetyan,Yury A Skorik,Ekaterina D Obluchinskaya,Irina M Lapina,Anna A Kulminskaya,Dmitry V Lebedev,Elena V Zhurishkina

doi:10.3390/biology10010067

Abstract

Simple SummaryThe continuous emergence of new pathogenic strains of bacteria resistant to antibiotics highlights the importance of search for the new natural sources of antimicrobial compounds. Fucoidans, sulfated polysaccharides from the cell walls of brown algae, attract the attention of many researchers due to their wide range of biological activities. Being natural and practically non-toxic, they are considered as a promising antimicrobial component that could, where possible, replace the use of strong chemical antiseptics and modern antibiotics. Natural fucoidans are polydisperse polysaccharides whose composition can vary greatly depending on the species, habitat, as well as on the way of purification. In this work, we investigate the structure and antibacterial properties of fucoidans from the brown algae Fucus vesiculosus gathered in the littoral of the Barents Sea. These fucoidans appear to have a significant bacteriostatic effect on the growth of four tested bacterial strains. Such an effect was more pronounced for crude fucoidan samples that did not undergo additional steps of purification.Fucoidans, sulfated polysaccharides found in cell walls of brown algae, are considered as a promising antimicrobial component for various applications in medicine and the food industry. In this study, we compare the antibacterial properties of two fractions of fucoidan from the brown algae Fucus vesiculosus gathered in the littoral of the Barents Sea and sampled at different stages of purification. The crude fraction of fucoidan was isolated from algae by extraction with aqueous ethanol and sonication. The purified fraction was obtained by additional treatment of the crude fraction with a solution of calcium chloride. The structural features of both fractions were characterized in detail and their antibacterial effects against several Gram-positive and Gram-negative bacteria were compared by photometry, acridine orange staining assay, and atomic force microscopy. Fucoidan inhibited growth in all of the above microorganisms, showing a bacteriostatic effect with minimum inhibitory concentrations (MIC) in the range between 4 and 6 mg/mL, with E. coli being the most sensitive to both fractions. Changes in the chemical composition after treatment of the crude fraction with a solution of calcium chloride led to a decrease in the content of sulfates and uronic acids and diminished antibacterial activity.

Highlights

Solving the problem of the continuous emergence of new pathogenic strains of bacteria resistant to antibiotics is one of the greatest challenges for modern medicine
Preparation of fucoidans: The thalli of F. vesiculosus L. collected in the autumn hydrological period (September 2018) in the Zelenetskaya Bay of the Barents Sea were used as raw material
Crude fucoidan F was isolated from F. vesiculosus brown algae of the Barents Sea by extraction with 5% ethanol solution at pH 4 and ultrasonic treatment according to a previously described patented method [20]

Summary

Introduction

Solving the problem of the continuous emergence of new pathogenic strains of bacteria resistant to antibiotics is one of the greatest challenges for modern medicine. Antibiotic-resistant infections cause about 700,000 deaths each year and, according to some forecasts, the global mortality rate from resistant bacteria could rise up to 10 million per year [1,2]. To reverse this trend requires design of new chemical antimicrobial substances, and an intensive search for new natural antimicrobial agents that could alleviate the current dependence of the modern medicine on traditional antibiotics. Various preparations containing fucoidans as a biologically active component are being developed for medical use, for example, in wound dressings [5,6]. The use of ultrasonic micronization of fucoidan as a food ingredient for the preparation of lactic acid products has been recently reported [7]

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