Structure of pigment compositions and radical scavenging activity of naturally green-colored cotton fiber

Naturally colored cotton fibers are apt to fade during fabric processing and home laundering due to the unstable accessory pigments. For the first time, this paper will report the chemical structure and radical scavenging activity of the pigment compositions of green cotton fiber. The hue of green cotton is actually yellowish green. Two yellow components in the pigment extract were isolated and identified as 22-O-caffeoyl-22-hydroxydocosanoic acid glycerol ester and 22-O-caffeoyl-22-hydroxydocosanoic acid, and both were radical-scavenging active compounds. The green cotton fiber showed scavenging capacities of 43.6 and 18.4 times, compared to that of common white cotton fiber toward 1,1-diphenyl-2-picrylhydrazyl and 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic radicals, respectively. This reveals an excellent radical scavenging property of green cotton fiber. Home laundering of green cotton fiber in the alkaline bath for 15 cycles resulted in 80-85 % loss of the radical scavenging capacity, whereas only 20-30 % loss was observed by the laundering in the neutral bath. The results presented here would be supportive for the processing and utilization of this ecological and functional cellulose fiber.