Traditional Tibetan medicine has extensively documented the health benefits of Dracocephalum heterophyllum. However, there are few reports on the chemical composition of furanocoumarins, probably because of their complicated isolation and purification procedures. In this study, four antioxidative furanocoumarins were isolated from Dracocephalum heterophyllum by medium- and high-pressure liquid chromatography in combination with on-line high-performance liquid chromatography-1,1-diphenyl-2-picrylhydrazyl recognition. Crude samples were sequentially pretreated by medium-pressure liquid chromatography using silica gel, MCI GEL CHP20P, and diol as stationary phases, whereas on-line high-performance liquid chromatography-1,1-diphenyl-2-picrylhydrazyl system was used to recognize antioxidant peaks in target fractions. Thereafter, the antioxidative peaks were separated and purified through high-pressure liquid chromatography to obtain four furanocoumarins with purities greater than 95%; namely isodemethylfuropinarine, demethylfuropinarine, alloimperatorin, and alloisoimperatorin. Finally, the antioxidant capacity of the isolated furanocoumarins was determined using in vitro experiments (1,1-diphenyl-2-picrylhydrazyl assays, molecular docking, and cellular validation) and it was concluded that nuclear factor erythroid 2-related factor 2 protein is a potential target of these compounds for their antioxidation effects. Thus, the proposed methodology exhibits excellent efficacy for the preparative isolation of high-purity antioxidative furanocoumarins from extracts of Dracocephalum heterophyllum and it can be efficiently utilized for isolating antioxidants from other natural products.
Keywords: Dracocephalum heterophyllum; antioxidant activity; high-pressure liquid chromatography; medium-pressure liquid chromatography; nuclear factor erythroid 2-related factor 2.
© 2022 Wiley-VCH GmbH.