Effect of alkaline solution on extraction efficiency and composition of natural brown cotton pigment

According to the fact that polyphenols compounds tend to solubilize in alkali,and in combination with ultrasonic-assisted extraction technology,alkaline solutions of different pH values were used to extract the natural brown cotton pigment. The results indicated that the alkaline solution has better extractability,and sodium hydroxide solution with a pH value of 14. 1 can extract most of the pigments from natural brown cotton fibers. The product extracted by deionized water turned neutral again after alkaline treatment and its UV absorption spectrum changed. The HPLC separation results also showed that some of the products extracted by alkaline solutions at different pH values will occur irreversible change,indicating that natural brown cotton pigments have multi-component structure and complexity. Hence,alkaline solution cannot be used for the pigment extraction from natural brown cotton,which is targeted for structural identification.