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. 2017 Oct 25;15(11):332.
doi: 10.3390/md15110332.

Determination of the Deacetylation Degree of Chitooligosaccharides

Yao Jiang  1   2 , Chuhan Fu  3   4 , Sihui Wu  5 , Guihua Liu  6 , Jiao Guo  7 , Zhengquan Su  8
Affiliations

Determination of the Deacetylation Degree of Chitooligosaccharides

Yao Jiang et al. Mar Drugs. .

Abstract

The methods for determination of chitosan content recommended in the Chinese Pharmacopoeia and the European Pharmacopoeia are not applicable for evaluation of the extent of deacetylation (deacetylation degree, DD) in chitooligosaccharides (COS). This study explores two different methods for assessment of DD in COS having relatively high and low molecular weights: an acid-base titration with bromocresol green indicator and a first order derivative UV spectrophotometric method for assessment of DD in COS. The accuracy of both methods as a function of molecular weight was also investigated and compared to results obtained using ¹H NMR spectroscopy. Our study demonstrates two simple, fast, widely adaptable, highly precise, accurate, and inexpensive methods for the effective determination of DD in COS, which have the potential for widespread commercial applications in developing country.

Keywords: 1H NMR; acid-base titration; bromocresol green; chitooligosaccharides; deacetylation; first-order derivative UV spectra.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

Figure 1
Figure 1
The molecular structures of COS (n = 2–20), COS: Chitooligosaccharides.
Figure 2
Figure 2
(A) 1H NMR spectrum (500 MHz,) of solutions of COSA in D2O; and (B) 1H NMR spectrum (500 MHz) of solutions of COSB in D2O.
Figure 2
Figure 2
(A) 1H NMR spectrum (500 MHz,) of solutions of COSA in D2O; and (B) 1H NMR spectrum (500 MHz) of solutions of COSB in D2O.
Figure 3
Figure 3
Comparison of zero-order UV spectra of different species of interest in this study, recorded in: water (A); 0.3 M acetic acid solution (B); and 0.3 M hydrochloric acid solution (C). Comparison of first-order derivative UV spectra of different species of interest in this study, recorded in 0.3 M hydrochloric acid solution (D).
Figure 4
Figure 4
Calibration curve from first-order derivative UV spectra of GlcNAc (16.0–120.0 μg/mL) in 0.3 M hydrochloric acid solution.
See this image and copyright information in PMC

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