“…The integrated areas for the resonances at 160-190 ppm (carboxyl, ester, amide) were 16%, 14%, and 12%, respectively, for these HA fractions, reflecting the expected decreases in carboxyl functionalities as the pH values of the extractants were raised. The contributions of amide functionalities to this resonance should not be overlooked because, for example, the contribution of amino acids to the overall composition of the HAs isolated at pH 12.6 was 16.3% (Hayes, 1996). The anomeric C resonances also increased as the pH of the extractant increased, indicating greater contributions of sugars to the compositions of the extracts.…”