Semi-synthesis of carboxyl-amino agarose

Chemical modification of biopolymers can produce functionalized molecules with broad applications.Agarose is a polysaccharide extracted from red seaweeds considered a suitable starting material for chemical modification, mainly because of its natural abundance and commercial availability¹,². In this work amino agarose, previously synthetized, was selectively oxidized, in the β-D-galactopiranose units by using 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) and trichloroisocyanuric acid (TCCA) as oxidants, producing an amphoteric and multifunctionalized polysaccharide. The colorimetric method to identify uronic acid³ was
positive and the FT-IR spectrum showed an absorption band at 1596 cm-1, attributed to –COO- group in the β-D-galactopiranosiduronic units. The HSQC NMR spectrum showed the disappearance of correlation at 63.4/3.76 ppm corresponding to C6/H6 of β-D-galactopiranose units and a new correlation was observed at 71.8/4.45 ppm, which was attributed to C4/H4 of galacturonic acid units. These results indicate the complete oxidation of the remaining C6 of the β-D-galactopiranose and the formation of the carboxyl-amino product.