OPTIMIZED EXTRACTION OF ANTIOXIDANT AGAR FROM THE Gracilaria domingensis RHODOPHYTA CELL-WALL ULTRASTRUCTURE

Antioxidant potential of Gracilaria domingensis sulfated polysaccharides (GdSPs) has have few explored. This study sequentially extracted and compared structural and antioxidant properties of GdSPs. After tissue digested with papain, in 100mM sodium acetate buffer+(pH 5)+5mM cysteine/EDTA, GdSPs were quantified and analyzed the molecular features (GdSPs-1→3) by agarose/polyacrylamide gels electrophoreses vs. standard glycosaminoglycans stained with toluidine blue or Stains-All; and structurally by infrared. Evaluation of antioxidant effects were in vitro tested by DPPH, total antioxidant capacity (TAC) and ferrous ion chelating methods against BHT, ascorbic acid (AA) and EDTA, respectively. Total yield was 44.82% considering three extractions, but GdSPs-3 was lowest (0.04%±0.01%, p<0.05) within all. GdSPs revealed agaran-structures presenting uronic acid and regularity in charge/size and functional groups along the algal matrix. GdSPs-1/-2 had concentration-dependent antioxidant responses, but there was a preponderance in TAC method, whose inhibitions were 81.57±0.54/72.55±1.37% at 4 mg mL-1, respectively, vs. AA (99.77% inhibition, 0.4 mg mL-1). GdSPs revealed a system of antioxidant agar along the wall-ultrastructure.