Oxidation of cashew tree gum exudate polysaccharide with TEMPO reagent

Cashew gum ( CG), an exudate polysaccharide from Anacardium ocidentale trees, was oxidized with TEMPO reagent and the 7product (CGOX) characterized by spectroscopic techniques ( FTIR and NMR), chromatographic analyses ( HPLC and GPC), viscosity measurements and thermal analysis (TGA). The yield of the reaction product was 96%. The uronic acid content in starting gum (7.2 m%) was increased to 36 m%. The degree of oxidation based on free galactose and glucose units was 68%. NMR data show that oxidation occurred preferentially at primary carbons of galactose units. High degradation degree after oxidation was estimated by the difference on the expected and observed eta(CGOX/)eta(CG) ratio. The presence of organic and inorganic impurities in the new polyelectrolyte was detected by TGA. A less thermally stable cashew gum is formed after the oxidation with TEMPO based on initial decomposition temperature and IPDT.