Search

International audience; This study aims to assess for the first time the ability of marine polysaccharides and their derivatives to stimulate natural defenses in olive tree leaves. Alginates, ALSM, and ALCM were isolated from the brown algae Sargassum muticum and Cystoseira myriophylloides, respectively. The OASM and OACM fractions were obtained after radical depolymerization of ALSM and ALCM, respectively. Three sulfated polysaccharides, arabinogalactans (AGB and AGP) and fucoidans (FUCCM) were extracted from the green alga Codium decorticatum and the brown seaweed C. myriophylloides, respectively. The extraction yield of different extracts was in the range of 0.82–32% and the average molecular weight (Mw) varied from 3000 Da to 2173 kDa. The M/G ratios of ALSM and ALCM were 0.87 and 1.12, respectively. FUCCM contained 53% of fucose and 12.83% of sulfates. The AGB and AGP fractions were characterized by the presence of a high degree of sulfation and protein (12–23% (w/w)) and were composed mainly of galactose, glucose, and arabinose. The aqueous saccharide solutions were applied to the leaf discs of the olive tree at 0.5 g/L, 1 g/L, and 2 g/L, for 24 h. These molecules triggered defense responses, by showing a differential capacity to induce the activity of the phenylalanine and tyrosine ammonia-lyase (TAL and PAL), polyphenols, and lignin contents in the leaves of the olive tree. Alginates and their derivatives as well as arabinogalactans exhibited an important induction of TAL activity compared to the PAL. The sulfated polysaccharides were more effective compared to the unsulfated polysaccharides (alginates) which were active at a low concentration. The optimum concentration for most of the studied elicitors was 2 g/L. These results suggest the valorization of these molecules derived from marine biomass as inducers of natural defenses of the olive tree to protect against phytopathogens in the context of sustainable development.

Sulfated glycoproteins extracted for the first time from the Moroccan green seaweed Codium decorticatum were investigated for their ability to induce a natural defense metabolism in the roots and the upper leaves of tomato seedlings. The crude (AGB) and the purified fractions (AGP) were characterized chemically (Colorimetric assays) and structurally (SEC-MALS, GC-EI/MS, ATR-FTIR). The elicitor aqueous solutions (1 g/L) were applied by foliar spray and syringe infiltration into the internodal middle of 45-day-old tomato seedlings. Phenylalanine ammonia-lyase (PAL) activity, polyphenols, and lignin contents were measured in the roots and the leaves after 0 h, 12, 24, 48, and 72 h of treatment. The AGB and AGP extracts contained 37.67% and 48.38% of the total carbohydrates, respectively, and were mainly composed of galactose, glucose, arabinose, and a minor amount of xylose and rhamnose. They were characterized by an important molecular weight (Mw) > of 2000 × 103 g·mol−1 and a high degree of sulfation and protein (12–23% (w/w)), indicating that the extracted polysaccharides could be an arabinogalactan-rich protein present in the cell wall of the green seaweed C. decorticatum. Both crude and purified fractions exhibited an elicitor effect by inducing the PAL activity, the accumulation of phenolic compounds and lignin contents in the roots and the leaves of tomato seedlings. These responses were systemic in both the methods used (injection and foliar spray) and were mobilized throughout tissues that are not directly treated (roots and/or leaves). Regarding the elicitor activities, AGB and AGP presented globally similar patterns, which revealed the importance of crude extracts in the stimulation of plant immunity. These results suggest the new application of sulfated glycoprotein isolated from green seaweed in agriculture as inducers of natural defenses of plants.

Today, an ethnobotanical approach makes sense for identifying new active bioactive chemicals from uses of indigenous plants. Two water-soluble enriched polysaccharide fractions (L-PSPN and S-PSPN) were extracted by hot water extraction from the leaves and seeds of Plantago ciliata Desf. (1798), a Mzab indigenous herb currently used in Algeria by traditional healers. Primary investigation was performed for describing the main structural features of these polysaccharides (pectin- and heteroxylan-like compositions) by using colorimetric assays, FTIR spectroscopy, HPAEC/PAD and GC/MS-EI analyses. Some biological activities were also monitored, such as anticomplement, anti-inflammatory (phagocytic ability, NOX2 and MPO inhibitions) and anti-diabetic (α-amylase and α-glucosidase inhibitions). L-PSPC seems able to moderately modulate innate immune system (IC50 around 100 µg/mL) and contribute to wound-healing processes (IC50 close to 217 vs. 443 µg/mL for sodium heparin). S-PSPC shows some potential as an anti-hyperglycemic (IC50 around 4.7 mg/mL) and anti-inflammatory (IC50 ranging from 111 to 203 µg/mL) agent, as well as other (fiber) psyllium-like polysaccharides extracted from Plantago species.

International audience; Polysaccharides are highly variable and complex biomolecules whose inventory of structures is still very incomplete, as nature still preserves unexplored biotopes. Plants, macroalgae and microalgae are an integral part of the daily life of human being regardless of culture, time, or knowledge development of a country. Natural medicine is an ancestral knowledge widely distributed throughout the world, handed down for centuries from generation to generation by those commonly referred to as “nganga” healers or shamans. It is also called alternative medicine or traditional medicine, and has been associated for millennia to legends. This review gives an emphasis regarding the ethnobotanic approach associated to the structural variability of poly- and oligosaccharides for designing the new polysaccharide-based drugs and hydrocolloids of tomorrow. The guiding thread is to survey the potential of plants (and some macroalgae) from Africa as a source of polysaccharides with original structures and, secondly, to correlate these structures with biological and/or functional properties in particular to address and advance the sustainable development and economic growth of mankind.