High-accuracy mass spectrometry for identification of sulphur-containing bioactive constituents and flavonoids in extracts of Raphanus sativus var. caudatus Alef (Thai rat-tailed radish)

The bioactive compounds of Raphanus sativus var. caudatus Alef and their respective cytotoxicity were identified from (a) 2 crude water and dichloromethane extracts and (b) 5 serially partitioned extracts using dichloromethane. Then, using a bioassay-guided cytotoxicity assay, the extracts were tested against the colon cancer cell line HCT116. Among 2 crude extracts and 5 fractions, the dichloromethane crude extract possessed the greatest in vitro cytotoxicity against HCT116. The dichloromethane crude extract was subjected to flash column liquid chromatography. Only 4 fractions and unfractionated extract were chosen for further analysis by high accuracy mass spectrometry (UHPLC-QToF-MS/MS). Six glucosinolates, 13 isothiocyanates, 5 indoles, 4 flavonoids, 2 alkaloids, 2 thiocyanates, 1 oxazolidine, and 1 dialkyl disulphide were identified. Two compounds were detected for the first time—isoalliin and butyl 1-(methylthio)propyl disulphide. Several constituents with anti-cancer activity were identified. This information could inform guidelines for quality control of standard plant extracts for further product development.