Table 4 The FT-IR functional groups of purified WK

3209.55

N-H stretching and O-H stretching

(superimposed bonds)

3086.11

Alkene C-H stretching

1651.07, 1589.34, 1514.91

C=O stretching, C=C stretching and

N-H bending

1411.89

O-H bending and C-N stretching (superimposed bands)

1087.85

C-O stretching

617.22

Alkene C-H bending