Freshwater plants synthesize sulfated polysaccharides: heterogalactans from Water Hyacinth (Eicchornia crassipes)

Abstract

Sulfated polysaccharides (SP) are found mainly in seaweeds and animals. To date, they have only been found in six plants and all inhabit saline environments. Furthermore, there are no reports of SP in freshwater or terrestrial plants. As such, this study investigated the presence of SP in freshwaters Eichhornia crassipes, Egeria densa, Egeria naja, Cabomba caroliniana, Hydrocotyle bonariensis and Nymphaea ampla. Chemical analysis identified sulfate in N. ampla, H. bonariensis and, more specifically, E. crassipes. In addition, chemical analysis, FT-IR spectroscopy, histological analysis, scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDXA), as well as agarose gel electrophoresis detected SP in all parts of E. crassipes, primarily in the root (epidermis and vascular bundle). Galactose, glucose and arabinose are the main monosaccharides found in the sulfated polysaccharides from E. crassipes. In activated partial thromboplastin time (APTT) test, to evaluate the intrinsic coagulation pathway, SP from the root and rhizome prolonged the coagulation time to double the baseline value, with 0.1 mg/mL and 0.15 mg/mL, respectively. However, SP from the leaf and petiole showed no anticoagulant activity. Eichornia SP demonstrated promising anticoagulant potential and have been selected for further studies on bioguided fractionation; isolation and characterization of pure polysaccharides from this species. Additionally in vivo experiments are needed and are already underway.

Keywords: biological activities; freshwater; sulfated galactan.

Figure 1

Electrophoresis of sulfated polysaccharides from E. crassipes. Aliquots of approximately 5 μL (250 μg) of Eicchonia polysaccharides or (5 μg) glycosaminoglycans were applied in agarose gel (10 × 7.5 cm, and 0.2 cm thick) prepared in 0.05 M 1,3-diaminopropane-acetate buffer pH 9.0, and subjected to electrophoresis at 110 V/cm for 60 min. Gels were then held in 0.1% cetyltrimethylammonium bromide for 2 h and dried. Polysaccharides were stained with 0.1% toluidine blue in a solution containing 50% ethanol and 1% acid acetic, in water, for 15 min. Gels were then de-stained using the same solution, without toluidine blue. R—root; Ri—rizhome; Pet—petiole; L—leaf; CS—chondroitin sulfate; DS—dermatan sulfate; HS—heparan sulfate; Or—origin.

Figure 2

Sulfated polysaccharide localization in different regions of the E. crassipes determined by histological analysis. Optical microscopy images of the root (A), rhizome (B) petiole (C) and leaf (D) of the E. crassipes showed differences in the staining intensity from toluidine blue represented by the arrows.

Figure 3

Scanning electron microscopy from E. crassipes root. Arrow, arrowhead, and asterisk indicate the points of collection of data for analysis of energy-dispersive X-ray analysis (EDXA). Arrow—epidermis; arrowhead—cortex; asterisk—vascular bundle.