Binding interaction between aloe polysaccharide and alizarin red by spectrophotometry and its analytical application

In order to aid the detection of and to reveal the physiological function of aloe polysaccharide (APS), spectroscopic studies of aloe polysaccharide and alizarin red (AR) interaction are presented in this work. APS was identified as an acetylated mannan, which consists of a polydispersed β-1,4-linked mannan substituted with O-acetyl groups. The binding interaction between APS and AR was investigated by experiments and theoretical calculation, respectively. The experimental value is in good agreement with the theoretical one. The results show that co-action of the electrostatic and hydrophobic interactions between AR and APS contributes to APS–AR complex chromogenic reaction. Based on this interaction, a new method for spectrophotometric determination of APS with AR is proposed. The maximum absorbances of the complex are at 325 nm and 516 nm. The corresponding linear equations are A = 0.0109ρ + 0.0441, R2 = 0.9992 and A = 0.0121ρ + 0.0288, R2 = 0.9988. The linear range is 0–60.00 μg/mL and the average recovery is 100.2 ± 5%, RSD ⩽5%.