Agars from Chilean Gelidiaceae

Abstract

Cystocarpic, tetrasporic and vegetative thalli of Gelidium chilense were extracted with water at 95 " C. The contents of 3,6-anhydro-galactose and sulfate group of the hydrocolloids correspond to those of an agar-type polysaccharide. The percentages of 6-O-methyl-galactose and of pyruvic acid ranged between 5.7-6.2% and 0.42-0.54%, respectively. The gel melting and gelation temperatures of Gelidium chilense, G. rex and G. lingulatum agars were determined. A correlation between 6-O-methylgalactose content and gelation temperatures was not observed. It was found by anion-exchange chromatography that 19.8% of tetrasporic and 4.9% of vegetative G. chilense agars are unsulfated polymers. Structural studies on the neutral fraction from tetrasporic G. chilense agar by partial hydrolysis and 'H NMR spectroscopy have shown that it is mainly composed of agarose. Methylation analysis, oxidative hydrolysis and partial hydrolysis, followed by 'H NMR spectroscopy, have shown that the neutral fraction of the agar from tetrasporic Gelidium rex is agarose. The results obtained in this work are compared with previously reported data on studies of agars from Chilean Gelidium species.

Biomedical applications of mesoporous silica particles

“…Agar solution (1% w/w) begins to gel when the solution cools to approximately 35 °C and will not subsequently melt unless the temperature is raised above approximately 80 °C [119]. Additionally, prolonged exposure to temperatures above the melting point degrade the mechanical stability of the agar gel formed once the temperature is lowered [120]. These temperature effects place a practical limit on the number and duration of alternating vortex mixing and sonication treatments that can be applied to the liquid mixture.…”