Composition Analysis of Pigment in Colored Cotton Fiber

Flavonoid and carotenoid are the main two kinds of plant pigments, but which kind of pigment is in colored cotton fiber has not been studied. In this paper, flavonoid and carotenoid content in colored cotton fibers was tested and content of flavonoid in brown (X008), green (S029) and white (Xuzhou 142) mature cotton fiber was 4.424 mg·g -1,3.846 mg·g -1 and 0.375 mg·g -1, respectively, but carotenoid was not detectable (Table 1). The pigment in colored cotton fibers was extracted by methanol at room temperature. The results of color reactions (HCl-Mg reaction, NaBH 4 reaction, NaOH reaction, FeCl 3 reaction and Pb(Ac) 2 reaction) of the pigment extractive showed that the pigment extracted by methanol was flavone or flavonol with two adjacent hydroxide groups (Table 2, Fig.1) . The results of UV spectral analysis further proved that the pigment extracted by methanol from brown fiber belonged to flavone with two adjacent hydroxide groups in B ring, and that from the green fiber contained not only flavone but also flavonols with two adjacent hydroxide groups both in A ring and B ring and indican replaced a hydroxide group at 3-site of A ring (Fig.2-4, Fig.6-7). Also, the green fiber pigment might include a compound of flavonol which has the similar molecular structure as rutin (Fig.5).