Serotonin, melatonin, and certain indole derivatives profiles in rutabaga and kohlrabi seeds, sprouts, bulbs, and roots

•Indole and its derivatives in rutabaga and kohlrabi were investigated.•Kohlrabi, rutabaga can be source of tryptamine, melatonin, l-tryptophan, serotonin.•Brassica sprouts (kohlrabi, rutabaga) are good source of melatonin and serotonin.•Rutabaga and kohlrabi sprouts-better source of melatonin than alfalfa or sunflower.

Rutabaga and kohlrabi provide valuable and beneficial constituents of human diet. Compounds such as tryptamine, melatonin, indole and methyltryptamine were determined in kohlrabi bulbs in the respective amounts of 1.38 ± 0.31, 0.78 ± 0.09, 0.32 ± 0.03 and 0.67 ± 0.09 μg/100 g fw. Rutabaga roots contained l-tryptophan, tryptamine, melatonin, serotonin and methyltryptamine in the amounts of 3.04 ± 0.95, 1.80 ± 0.20, 0.56 ± 0.09, 0.16 ± 0.06 and 0.98 ± 0.04 μg/100 g fw, respectively. In their seeds three compounds (μg/100 g fw) were found, namely serotonin (0.36 ± 0.05) and l-tryptophan (21.97 ± 1.07) in rutabaga seeds, whereas in kohlrabi seeds serotonin (4.00 ± 0.07) and indole (0.31 ± 0.01). Evaluated sprouts contained more indole derivates than seeds. Serotonin was observed solely in rutabaga sprouts, in rather small amounts 0.10 ± 0.00-0.38 ± 0.06 μg/100 g fw. Melatonin concentrations in 8 days sprouts of rutabaga and kohlrabi were at the level of 0.51 ± 0.11 and 0.70 ± 0.02 μg/100 g fw, respectively. As relatively high concentrations of indole derivates were detected in rutabaga and kohlrabi, both in ripe plants and their sprouts, these vegetables provide an important source of such compounds.