Table 2.
FTIR spectrum analysis of functional groups of LP1-3.
| Absorption (cm−1) | Functional group | Structural characteristic | |||
|---|---|---|---|---|---|
| LP1 | LP2 | LP3 | |||
| 3398.0 | 3431.8 | 3430.9 | hydroxyl group (-OH) | stretching vibration of O-H | |
| amino group (-NH2) | stretching vibration of N-H | ||||
| 2924.6,2853.1 | 2928.0 | 2930.4 | alkyl group (-CH2-) | stretching vibration of C-H | |
| 1742.9 | carboxyl group (-COOH), aldehyde group (-CHO) or esterfunction (-COOR) | stretching vibration of C=O | |||
| 1654.5 | 1638.0 | 1647.4 | carbonyl group (-C=O or -CHO) | stretching vibration of C=O | |
| amide group (-NH2 or –COR) | bending vibration of N-H or stretching vibration of C=O | ||||
| amino group (-NH2) | bending vibration of N-H | ||||
| bound water | |||||
| 1541.3 | amino group (-NH2) or amide group (-NH2) | bending vibration of N-H | |||
| carbonyl group (-C=O) | stretching vibration of C=O | ||||
| 1457.9 | 1458.8 | 1458.0 | alkyl group (-CH2- or –CH3) | bending vibration of C-H | |
| 1418.8 | 1425.2 | carboxyl group (-COOH) | stretching vibration of C-O | ||
| 1378.2 | 1364.2 | 1363.6 | carboxyl group (-COOH) | symmetrical stretching vibration of C=O | |
| 1237.7 | 1275.1, 1209.1 | 1270.0 | carboxyl group (-COOH) | bending vibration of O-H | |
| 1159.1 | 1157.9 | ether (-C-O-C-) | stretching vibration of C-O | ||
| 1053.2 | 1043.9 | 1013.1 | hydroxyl group (-OH) | bending vibration of O-H | |
| 918.0 | 920.8 | D-glucopyranose ring | antisymmetrical ring vibration | ||
| 865.0 | furanose | ||||
| 847.9 | α-type glycosidic linkage | bending vibration of C-H | |||
| 819.6 | α-D-galactopyranose | ||||
| 764.2 | 776.2 | D-glucopyranose ring | symmetrical ring vibration | ||