Sulfated polysaccharide extracted from the alga Gracilaria domingensis modified with propionic anhydride negatively modulates acute inflammation and experimental hypernociception

Abstract

Sulfated polysaccharides (PLSs) from marine algae represent a broad class of compounds with pharmacological interest, due to their therapeutic properties. PLSs have hydrophilic chains containing various chemical groups of several compositions that differ structurally and in their physicochemical and biological effects. However, this hydrophilic nature of PLSs is also responsible for some limitations in the use of these compounds. To overcome these disadvantages, PLSs can be chemically modified by grafting groups that can give the compound a more hydrophobic nature. In the present study, the PLS from Gracilaria domingensis was modified with propionic anhydride (PLS-AP) and underwent complementary characterizations by scanning electron microscopy, X-ray diffraction, infrared spectral analysis and elemental analysis. The reaction with propionic anhydride increased crystallinity and produced a chemically modified polysaccharide with new carbon, hydrogen and sulfur groups. The new characteristic of the compound may have added interesting properties to PLS, such as increased stability, amphiphilic nature and increased sulfate content, which in red marine algae SPSs produce biological activity. Regarding biological properties, PLS-AP (2.5 mg/kg) significantly reduced paw edema induced by carrageenan, histamine, serotonin, bradykinin and prostaglandin E2, as well as improved microscopic tissue damage criteria. The modified compound was also able to significantly decrease neutrophil migration, myeloperoxidase, and malondialdehyde concentrations and preserved glutathione levels in peritoneal fluid during induced peritonitis. Additionally, in antinociceptive tests, PLS-AP reduced the number of contortions induced by acetic acid and the response time to formalin-induced paw licking. Thus, PLS-AP may be a promising substance to treat inflammatory conditions.