The contents of five antioxidants and the abilities of four antioxidative functions were determined in eight insect galls and their six host plants leaves. The grey relational order indicated that scavenging DPPH free radicals ability was strongly related to polyphenols and carotenoids, chelating ferrous ions activity strongly related to anthocyanins and polyphenols, superoxide anion scavenging activity related to polyphenols and flavonoids, and reducing power related to carotenoids and polyphenols. The preference order evaluated by grey decision making for antioxidative capacity was Schlechtendalia Chinensis (gall) > Daphnephila sueyenae (gall) > Unknown sp. 2 (gall) > Daphnephila taiwanensis (Gall) > Bruggmanniella sp. (gall) > Ceratovacuna nekoashi (gall) > Styrax suberifolia (leaf) > Sycopsis sinensis (leaf) > Styrax formosana (leaf) > Unknown sp. 1 (gall) > Litsea acuminata (leaf) > Machilus thunbergii (leaf)> Pseudoregma bambucicola (gall) > Ficus erecta var. beechyana (leaf). The contents of polyphenols were the most relevant to the antioxidant ability, and that of chlorophylls is the less. The galls had higher antioxidative capacity than their host leaves to scavenge free radicals effectively for balancing the increases of free radicals in their bodies.
