Comparison of Antioxidant Activities of Melanin Fractions from Chestnut Shell.
Chestnut shell melanin can be used as a colorant and antioxidant, and fractionated into three fractions (Fr. 1, Fr. 2, and Fr. 3) with different physicochemical properties. Antioxidant activities of the fractions were comparatively evaluated for the first time. The fractions exhibited different antioxidative potential in different evaluation systems. Fr. 1, which is only soluble in alkaline water, had the strongest peroxidation inhibition and superoxide anion scavenging activity; Fr. 2, which is soluble in alkaline water and hydrophilic organic solvents but insoluble in neutral and acidic water, had the greatest power to chelate ferrous ions; and Fr. 3, which is soluble both in hydrophilic organic solvents and in water at any pH conditions, had the greatest hydroxyl (·OH) and 1,1-diphenyl-2-picryl-hydrazyl (DPPH·) radicals scavenging abilities, reducing power, and phenolic content. The pigment fractions were superior to butylated hydroxytolune (BHT) in ·OH and DPPH· scavenging and to ethylene diamine tetraacetic acid (EDTA) in the Fe(2+)-chelation. They were inferior to BHT in peroxidation inhibition and O₂·(-) scavenging and reducing power. However, BHT is a synthetic antioxidant and cannot play the colorant role. The melanin fractions might be used as effective biological antioxidant colorants.
Key Laboratory for Forest Resources Conservation and Use in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China. z-yyao@hotmail.com.
Zeng-Yu
ZY
Yao
Key Laboratory for Forest Resources Conservation and Use in the Southwest Mountains of China, Ministry of Education, Southwest Forestry University, Kunming 650224, China. jhqi1977@163.com.
Jian-Hua
JH
Qi
D031319:Aesculus / Q000737:chemistry*; D000975:Antioxidants / Q000494:pharmacology*; D002614:Chelating Agents / Q000737:chemistry; D005505:Food Coloring Agents / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D015227:Lipid Peroxidation / Q000187:drug effects*; D008543:Melanins / Q000494:pharmacology*; D010936:Plant Extracts / Q000494:pharmacology
D000975:Antioxidants; D002614:Chelating Agents; D005505:Food Coloring Agents; D016166:Free Radical Scavengers; D008543:Melanins; D010936:Plant Extracts
Castanea mollissima; colorant; free radical; pigment