A. Romanotto, M. Gruenwald
The known source of the very important, health-relevant secondary plant metabolite, sulforaphane (SFN) developed from glucosinolates (GSL), is the plants of the Brassicaceae family. This is primarily broccoli, but includes also garden cress, cabbage, mustard etc. [1]. The known precursor for SFN in broccoli was glucoraphanin (GPN) [2].
Nowadays, fermentation is no longer only the procedure, to protect food against spoilage, but also has numerous health benefits [3]. Nasturtium (Tropaeolum majus L) belongs to the Tropaeolaceae family and, like the members of the Brassicaceae family, also contains GSL, but not GPN. We tested whether SFN can be formed during lactic acid fermentation in Nasturtium. The measurement technique used was UHPLC-MSMS after extraction with methanol.
In our analysis, fully and short fermented and non-fermented leaves and flowers of nasturtium were examined for their metabolic development with LC-HR-MS. One of the matches in fermented product was SFN.
In the next step we analysed our samples for the presence and quantification of SFN and also GPN with the established LC-MSMS measurement. Clear amounts of SFN were found in the fermented products. GPN was not found at any time. We were thus able to prove, that SFN can also be formed from the other GSL apart from GPN during lactic acid fermentation. The source for SFN is also not only plants of the family Brassicaceae.
In addition, through anaerobic lactic acid fermentation, SFN which is very sensitive to oxygen, can generally be stabilized and naturally protect SFN.
References:
[1] Avato P., Argentieri M.P. Brassicaceae: A rich source of health improving phytochemicals. Phytochem. Rev. 2015; 14:1019–1033. doi: 10.1007/s11101-015-9414-4.
[2] Janczewski, L., Sulforaphane and Its Bifunctional Analogs: Synthesis and Biological Activity, Molecules. 2022 Mar; 27(5): 1750; doi: 10.3390/molecules27051750
[3] J.R. Wilburn, E.P. Ryan, Chapter 1 – Fermented Foods in Health Promotion and Disease Prevention: An Overview, Fermented Foods in Health and Disease Prevention, 2017, Pages 3-19, Academic Press; https://doi.org/10.1016/B978-0-12-802309-9.00001-7