Phytochemical Content of the Kale (Brassica oleracea L. var. acephala) Leaves and Seasonal Variation of Antioxidant Activity

Kale (Brassica oleracea L. var. acephala), with its antioxidant and phytochemical properties, helps reduce the risk of many cancers and heart disease. In this study, the natural (intact) glucosinolate, total phenolic and flavonoid content, antioxidant activity and fat content of leaf extracts of kale leaves, which is known to be unique to the Black Sea while is a Mediterranian plant, were investigated. Kale was grown in the conditions of Kahramanmaras and Kale leaves collected at two weeks intervals from November 28, 2014 until March 24, 2015. The leaves were dried on a lyophilizer and extracted with methanol. As a result of HPLC analysis, six different natural glucosinolates were determined in different amounts, namely sinigrin, progoitrin, epiprogoitrin, gluconapine, glucoerusin and glucocorticin. As a result of GC-MS analysis of the oil obtained from the Kale extracts, 33 different fatty acids were identified. The highest contents of these fatty acids were trichosanoic acid (28.25%), cis-11-eicosanoic acid (24.01%), linoleic acid (10.13%), palmitic acid (9.35%) and butyric acid (7.76%). The antioxidant capacity of Kale leaves increased until the end of January and then decreased. Temperature on these dates has fallen until January, after January temperature has begun to rise. Total phenolics value of plant leaves collected between these dates was 7.32-11.63 mg g-1, total flavonoid amount 2.01-3.96 μg g-1, FRAP value 13.43-29-77 μg g-1 and DPPH value 1.31-1.91 mg g-1