Kale contains a large amount of vitamin K. It is a rich source of vitamin A, C (ascorbate), B6, K, folate and manganese, as well as indoles, thiamin, riboflavin, pantothenic acid, vitamin E and several dietary minerals, including iron, calcium, potassium, and phosphorus. Kale is a source of the carotenoids lutein and zeaxanthin. It also contains glucosinolate compounds such as glucoraphanin, which contributes to the formation of sulforaphane, a compound under preliminary research for its potential to affect human health. Kale contains high levels of polyphenols, such as ferulic acid.