Indole -3-carbinol is a nonessential nutrient derived from glucobrassicin found in garden cress, mustard greens, Brussels's sprouts, horse radish, kale, kohlrabi, rutabaga, turnip, cabbage, broccoli and cauliflower. (nutrientsreview.com)
I3C in turn is a by - product of glucosinolate glucobrassicin, a compound found in cruciferous vegetables like broccoli, cauliflower, kale, brussel sprouts and cabbage. (supernaturalacnetreatment.com)
However, the amount of total glucosinolates and the amount of indole -3-carbinol formed from glucobrassicin in food is variable and depends, in part, on the processing and preparation of foods (for more detailed information, see the article on Cruciferous Vegetables). (lpi.oregonstate.edu)