Abstract: Many scholars used different methods for brown cotton pigment extraction, which results in significant difference on qualitative. According to the alkali-soluble ability of polyphenols, with ultrasound-assisted extraction technology, we use different pH alkaline solution for natural brown pigment extraction. The results indicated that the alkali solution has better extractability, which PH value is 14.1, can extract most of the pigments from natural brown cotton fiber. The UV spectrum of pigments solution changed which extracted by deionized water repatriation neutral after alkali treatment. The HPLC separation results also showed that some substances changed which extracted by alkaline solutions. Natural brown cotton pigments have multi-component structure and complexity. Alkali solution cannot be used for the pigment extraction from natural brown cotton, which purpose is structural identification.

Key words: natural brown cotton, pigment, aldaline solrtion extraction, conposition