Distribution of glucosinolates and antioxidants in different leaf-layers of Kale (Brassica oleracea var. acephala DC.).

Abstract

Abstrast. Kale (Brassica oleracea var. acephala DC.) has attracted much attention due to its ornamental value and nutritional benefits. Its health-promoting properties, such as anti-cancer, anti-tumor, and antibacterial effects, are mainly attributed to its high content of glucosinolates (GSLs) and antioxidant compounds. However, the patterns of nutrient accumulation in the inner and outer leaves of kale, as well as the factors influencing these patterns, remain poorly understood. This study investigated the distribution of GSLs and antioxidant activities between the inner and outer leaves of two kale varieties and evaluated the expression profiles of genes related to GSL biosynthesis. The results showed that the GSL content and DPPH scavenging activity were significantly higher in the inner leaves of both kale varieties compared to the outer leaves. In contrast, the outer leaves exhibited significantly higher concentrations of chlorophyll, ascorbic acid, total flavonoids, and anthocyanins. Moreover, the expression patterns of genes associated with aliphatic, indolic, and aromatic GSL biosynthesis were consistent with the observed GSL content. Our findings suggested that the distribution of metabolites in kale is predominantly influenced by developmental stage of leaves, which warrants further investigation.