AOAC SPDS Mid Year 2016

Existing Methods • Colorimetric Assay by Red Dye – Alizarin Red

– Gu et al ., Binding interaction between aloe polysaccharide and  alizarin red by spectrophotometry and its analytical application.  Carbohydrate Polymers. 2010 , 80 , 115–122.

O OH

OH

+

Aloe polysaccharides

- Na +

SO 3

O alizarin red

• Complex of alizarin red with polysaccharides and assayed  at 325nm and 516nm

Existing Methods • Colorimetric Assay of Acetyl Groups of Polysaccharides – Aloe Products for Food Raw Material, Chinese National Standard,  QB/T 2489 2007

O O Fe /3

O

O

1/3Fe 3+

NH 2 OH

OH

R

N H

N H

O

Ferric - Acethydroxamic Acid Complex

Acetohydroxamic Acid

Th t l • e ace y groups on po ysacc ar es are reac e w  hydroxylamine to form acetohydroxamic acid.  The  resulted acetohydroxamic acid is reacted with ferric  trichloride to form a ferric‐acethydroxamic acid complex  and measured 540nm. l h id t d ith