3.1.3 FT-IR analysis
The GP was analyzed by FT-IR spectra with recorded frequencies ranging from 4,000 to 500 cm-1 (Fig. 1C). A wide absorption peak at 3,446 cm-1 in the region of 3,500-3,200 cm−1 showed stretching vibrations of O-H and N-H, indicating intramolecular hydrogen bonds. Two peaks in the 3,000-2,800 cm-1 region and the 1,400-1,200 cm-1region were angular vibrations of C-H, which indicated that the GP is a polysaccharide compound. The peak at 1,633 cm-1indicates the stretching vibration of the C = O in the acetyl group. The absorption peak at 789 cm-1 is the flat pyranose α-type C-H bond in the sugar units.