Investigation of glucosinolates, and the antioxidant activity of Dolsan leaf mustard kimchi extract using HPLC and LC-PDA-MS/MS

Leaf mustard (Brassica juncea), the main ingredient of leaf mustard kimchi, has a variety of biologically active secondary metabolites such as glucosinolates (GSLs), flavonoids, and polyphenols. In this study, the changes in GSL content and antioxidant properties during the storage of Dolsan leaf mustard kimchi (DLMK) for 35 days were examined by separation and purification of DLMK extracts using high-performance liquid chromatography (HPLC) and preparative octadecylsilane-HPLC. The total GSL content and antioxidant activity of the DLMK extracts had significantly lower values on day 21 of storage (p <.05). GSLs were detected in a single extract of DLMK using liquid chromatography-tandem mass spectrometry. The GSLs detected throughout most of the storage period (sinigrin, gluconapin, and glucotropaeplin) were different from those detected on day 21 of storage (glucobrassicin and progoitrin), when the antioxidant activity was low. Thus, GSLs may contribute to the antioxidant activity of DLMK. Practical applicationsDolsan leaf mustard kimchi (DLMK) is expected to have biological effects owing to the properties of its various ingredients, but the effects of fermentation and the overall composition of DLMK on physiological activity have not been determined. On the basis of this study, DLMK has high value as a natural antioxidant, but the antioxidant activity varies with fermentation time, which is lowest on day 21. Thus, these results can be used to establish appropriate preparation conditions for DLMK as a functional food.