Abstract:

Abstract Based on polyphenols pigment of natural green cotton and its structural instability, the scavenging 1- diphenyl - 2 –picrylhydtazyl (DPPH) radical method was used to study the effects of temperature, light irradiation, acid-base condition on the antioxidant activity of green cotton pigment. The results showed that high alkali conditions had great influence on the antioxidant stability of natural green cotton. The DPPH radical scavenging activity of green cotton pigment fell to 2.97% ,when the pigment was treated in the alkali solution with the pH value of 13.When adjusted to neutral, green cotton pigment recovered to 81.38% of its original radical scavenging ability, indicating that most of radical scavenging ability lost resulted from the alkaline condition was recoverable. The ultraviolet spectra measurements demonstrated that the main structure of pigment was unchanged when in the alkaline condition, but the structure of some components of the pigment had changed irreversibly .Light irradiation had significant effect on antioxidant activity of the pigment of naturally green cotton. The radical scavenging ability of green cotton pigment dropped to 57.10% when the pigment was exposed to the sun light for 5 days. It was found that on significant change in radical scavenging ability of green cotton pigment was caused, when treating the pigment at 150 ℃ for 1 h.