Level of Vitamin C, Polyphenols, and Antioxidant and Enzymatic Activity in Three Varieties of Kale (Brassica OleraceaL. Var.Acephala) at Different Stages of Maturity

The aim of this present study was to determine the level of vitamin C, L-ascorbic acid, polyphenols, antioxidant activity, peroxidase, polyphenol oxidase, and catalase in the leaves of three varieties of kale at different stages of maturity. Average values per 100 g of fresh matter were 102 mg of vitamin C (of which L-ascorbic acid constituted 97%) and 359 mg polyphenols; antioxidant activity was measured at 48.9% RSA (17.6 μM Trolox/g kale). Redbor1 c.v. variety contained the highest levels of the analyzed constituents. Compared with the first stage of maturity, plants at the second stage showed increases of 6% in vitamin C; 28% in polyphenols; and 12% in antioxidant activity, whereas plants at the third stage showed 5, 48, and 22% increased values, respectively. Average POD activity was 7.58 ΔA/min/g, PPO 1.64 ΔA/min/g, and CAT 7.93 mg H2O2/min/g. PPO activity increased with the age of the plant. No consistent correlation was found between the stage of growth and the other enzymes.