Characterisation and properties of Acacia senegal (L.) Willd. var, senegal with enhanced properties (Acacia (sen) SUPER GUM™): Part 3 Immunological characterisation of Acacia (sen) SUPER GUM™

Abstract

Four Acacia senegal samples, one control ( M w 6.2×10 5 g/mol) and three enhanced samples with different molecular weights ranging from 1.2×10 6–2.5×10 6 g/mol were fractionated using hydrophobic interaction chromatography (HIC) into two fractions, hydrophilic (fraction 1, yield ∼80%) and hydrophobic (fraction 2, yield ∼2%). The elution profile and weight average molecular weight of fraction 1 were similar to the starting materials but contained slightly more arabinogalactan protein (AGP) component. On the other hand, the AGP peak was almost completely removed from Fraction 2. The M w for fraction 2 was ∼1.1×10 5 g/mol and contained <0.5% (of the total injected mass) of aggregated materials with M w>4.9×10 7 g/mol. These fractions plus the whole gum were also analysed by ELISA (enzyme linked immunosorbent assay). The results showed that the interaction with an A. senegal specific antibody (SY CC7) is the same for the whole gum sample and its fractions, indicating a common, widely distributed epitope. One sample with the highest molecular weight (2.5×10 6 g/mol) showed a slightly different interaction, displaying a lower sensitivity, attributed to the formation of a more compact hydrophobic form of AGP. This is in accord also with the observations on the same sample using spectroscopic methods which was attributed to dehydration of the COOH uronic acid group. Examination of the commercially available Acacia(sen) SUPER GUM™ (EM2— M w ∼1.8×10 6 g/mol) with three different antibodies (SY CC7, UC-SEN-PS-01 and UC-SEY-PS-01) showed the response to be identical to that of control A. senegal gum. These results demonstrate how immunological techniques, in this instance ELISAs, can be utilised to indicate differences between gum samples and to determine the limit of maturation of Acacia(sen) SUPER GUM™.