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In order to develop innovative methods for the production of bioactive extracts with potential health benefits, enzyme-assisted extraction has been applied for the bioconversion of Ulva armoricana (Ulvales, Ulvophyceae). The extraction yields, chemical composition, the antioxidant and antiviral activities were determined to assess the efficiency of six commercial enzymatic preparations. Endoprotease treatments significantly increased the extraction yields compared to the control. The organic matter, neutral sugar and protein contents were increased in all extracts compared to an extraction with water, up to 2.0-fold, 2.7-fold and 1.75-fold, respectively. The samples prepared by a multiple-mix of glycosyl-hydrolases and an exo-β-1,3(4)-glucanase revealed activities against herpes simplex virus type-1 at the median effective concentration (EC 50 ) of 373.0 ± 20.7 and 320.9 ± 33.6 μg/ml, respectively. These activities were correlated to high amounts of rhamnose, uronic acids and sulfate groups which are the main constituents of ulvans. Free radical scavenging capacity at medium inhibition concentrations (IC 50 ) of 1.8 and 12.5 mg/ml was shown for the extracts produced with endo-protease treatments and 6.0 mg/ml for the sample resulting from the extraction with the multiple-mix of glycosylhydrolases. This study reports the antiviral and antioxidant activities of Ulva armoricana extracts produced by enzyme-assisted extraction. Rhodophyta [1] and Chlorophyta [2], but the most widespread are caused by the 52 Chlorophyta species, such as those within the genus Ulva Linnaeus [3]. During the last 53 few decades, the coasts of Brittany (France) have suffered from significant green tides 54 mainly constituted of non-attached populations of Ulva armoricana and Ulva rotundata 55 (Ulvophyceae) [2]. Many studies have addressed the ecological and environmental 56 consequences of green tides which include uncoupled biogeochemical cycles, decreased 57water transparency, degradation of the intertidal environment, reduced biodiversity, 58 hypoxia or anoxia, destruction of the marine coastal habitat (e.g., seagrass beds) and 59 economic losses to marine industries [3]. However, these seaweed beachings also 60 represent a huge algal biomass which could be exploited, for applications as plant 61 elicitors, in animal health and in feed [4,5,6]. 62At this time, harvesting of these seaweeds remains the most cost-effective way to obtain 63 a high tonnage of biomass. However, as the resource is unpredictable, aquaculture can 64 be an alternative in order to ensure its availability and improve the quality and 65 homogeneity of the resource. 66 Over the last few years, there has been more investigations in the research into new 67 bioactive natural molecules and valuable metabolites from seaweeds having an 68 economic impact [4,7]. Several biological activities such as antiviral [6], antibacterial 69 [8], antioxidant [9], anticoagulant [10] and antitumoral [11] have been identified in red 70 (Rhodophyta) and brown (Phaeophyta) algae but few s...

International audienceProliferations of green, brown and red algae appear in shallow sandy bays in North Brittany (France), and they represent a real economic constraint for the affected communities. In addition to the nuisance for residents and tourist activity, the communities must carry out systematic collection. The collected algae are spread on agricultural land spreading or composted, but these solutions reach their limits rapidly, bringing little added value to the collected algae. Seaweeds are potentially excellent sources of bioactive metabolites that could represent useful leads in the development of new functional ingredients in pharmaceutical and cosmetic industries. The aim of this study was to propose the use of an enzyme-assisted extraction as a tool to improve the extraction efficiency of antiviral compounds from three invasive French seaweeds. We selected the red Solieria chordalis, the green Ulva sp. and the brown Sargassum muticum as models for these experiments. In comparison with water extraction at 50 °C for the same time of treatment, enzymatic hydrolysis increased the yields. The data suggest the potential of enzymatic hydrolysis for producing active fractions in the function of the algal biomass, the behaviour of the cell wall, the selectivity and the action of the enzyme. Enzymatic hydrolysis appeared less effective for polyphenol recovery, but was a promising softer technique for recovering proteins, neutral sugars, uronic acids and sulphate groups. The solvent-free process, higher extraction rate and higher yields, coupled to time-saving and lower cost, make this method economical and sustainable. By using a cell viability assay, all hydrolysate fractions tested were shown to be non-toxic to Vero cells. After 3 days of treatment, no microscopically visible alteration of normal cell morphology was observed even at 500 μg mL−1. S. chordalis extracts have an effective antiviral activity with EC50 between 23.0 and 101.1 μg mL−1 at a multiplicity of infection of 0.001 ID50/cells; 100 % and 98 % cellular protection were obtained for 500 μg mL−1 of hydrolysate extracts carbohydrase C3 and blank, respectively. Other extracts from S. chordalis inhibited viral production less effectively