Bioassay-guided fractionation approach for determination of protein precursors of proteolytic bioactive metabolites from macroalgae

International audienceIn the last decades, an upsurge in the occurrence of chronic diseases caused by hypertension and oxidative stress has been observed. The objective of this research was to isolate and characterize groups of antioxidant and anti-hypertensive natural bioactive peptides originating from hydrolyzed proteins of the red seaweeds Solieria chordalis and Palmaria palmata, the green seaweed Ulva lactuca and the brown seaweed Saccharina longicruris. Enzymatic hydrolysis by trypsin and chymotrypsin was performed in order to release bioactive algal peptides. Three antioxidant assays, 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric ion reducing antioxidant power (FRAP) and oxygen radical absorbance capacity (ORAC), were used to determine the activity of seaweed peptides. Angiotensin-converting enzyme (ACE) inhibition assay was used to evaluate the anti-hypertensive potential. Additionally, liquid chromatography-tandem mass spectrometry (LC-MS/MS) analyses and database searches allowed for protein identification, indicating where these bioactive peptides originated from. Fractions of red seaweeds, especially S. chordalis, produced by chymotrypsin and trypsin hydrolysis, exhibited higher in vitro antioxidant and ACE inhibitory activities than the parent proteins. Size exclusion chromatography highlighted two groups of bioactive peptides: (i) peptides with molecular weight (MW) between 1,400 and 3,200 Da displaying antioxidant activities and (ii) smaller peptides (MW <1,000 Da) displaying both antioxidant and ACE inhibitory activities. LC-MS/MS analyses of the antioxidant subfractions of P. palmata and S. chordalis were performed, and several peptide sequences were elucidated, using tandem mass spectrometry. Of all identified peptides of S. chordalis, 61 and 43 % came from the hydrolysis of ribulose-1, 5-biphosphate carboxylase/oxygenase (RuBiSCo) enzymes. Phycoerythrin, elongation factors, photosystems and cytochrome oxidase clusters represented between 3 and 14 % of identified peptides in S. chordalis fractions. This is the first time, to the author’s knowledge, that distinction between several groups of bioactive peptides, within seaweed protein hydrolysates, has been reported. In addition, proteins of origin were also identified

Carrageenan from Solieria chordalis (Gigartinales): Structural analysis and immunological activities of the low molecular weight fractions

International audienceThe investigations reported here are about a carrageenan extracted from the abundant red alga, Solieria chordalis (Gigartinales) settled along the coasts of Brittany. Its structural features were characterized by GC―MS, 13C NMR and FTIR spectroscopies. The structural components of this polysaccharide are mainly a (DA2S-G4S)-type structure in association with methylated-L-carrageenan, pyruvated α-carrageenan and the minor precursor, v-carrageenen, in small amounts. The relative molecular weight of the native polysaccharide was estimated by LP-GPC as 913 kDa. The low molecular weight fractions (below 20 kDa) obtained by free-radical depolymerization and mild-acid hydrolysis presented substitution patterns similar to those of the native polysaccharide. These fractions proved to be devoid of direct cytotoxicity on Daudi (human Burkitt's lymphoma), Jurkat (human leukaemic T-cell lymphoblast) and K562 (human chronic myelogenous leukaemia) cells lines. On the other hand, they showed great immunostimulating properties: enhancement of neutrophil phagocytosis, cytotoxicity by natural killer cells, antibody-dependent cell cytotoxicity and stimulation of lymphocyte proliferation. Further to these investigations, it could be worth using the low molecular weight fractions of carrageenan from the red alga, S. chordalis, in immunotherapeutic approaches to cancer treatment

Concise review of the genus Solieria J. Agardh, 1842

International audienceSolieria spp. (Solieriaceae, Gigartinales, Rhodophyta) can be found in various habitats ranging from the marine environment to low-salinity estuarine environments. Of the commercially exploited carrageenophytes, some of the most abundant belong to the Solieriaceae family as, Kappaphycus, Eucheuma and Solieria. The supply of these seaweeds is ensured by their mastered culture and by large quantities of stranded wild seaweeds which are harvested. Rich in carrageenans, i.e., in linear sulfated galactans, these red macroalgae are widely used for their gelling, thickening, and stabilizing properties in food, cosmetic, or pharmaceutical industries. In addition, Solieria spp. provide scientific potential as a model for the development of cultures in Integrated Multitrophic Aquaculture (IMTA), for innovation in extraction and purification processes and in biorefineries to access to bioactive compounds. The genus Solieria was described using the species Solieria chordalis as the type species in 1842. Today, this species is found in large quantities on the beaches of the western Atlantic just like Solieria filiformis found on the other side of the Ocean on some beaches in Mexico. Due to its abundance, several scientific teams from France and from Mexico study these algae with high potential in nutrition, health and for environmental applications. Eight other species of the genus Solieria have been inventoried, the last one in 2018. Nevertheless, their abundance is lower as well as the number of scientific studies mentioning them. Therefore, in this review, we focus on the biology, ecophysiology, biochemical composition, and applications of Solieria spp. based mainly on the two species widely studied, namely Solieria chordalis and Solieria filiformis