Zwitterionic hydrophilic interaction liquid chromatography coupled to mass spectrometry for analysis of beetroot juice and antioxidant interactions between its bioactive compounds

Hydrophilic interaction liquid chromatography coupled to mass spectrometry (HILIC - MS) was employed to determine selected bioactive compounds (polyphenolics and vitamins B) in beetroot (Beta vulgaris L.) juice. Appropriate optimization of the method allowed to select the separation conditions and to increase the sensitivity of the method in comparison with RP mode. The limits of detection on ZIC HILIC column were 0.01 mg L−1 for flavonoids and phenolic acids, and 0.03 mg L−1 for vitamins B. The investigation of interaction between the major phenolic acids (protocatechuic and caffeic) and B vitamins (nicotinamide and panthotenic acid) found in beet juice was evaluated. Antioxidant activities of single components and their mixtures were determined by the mostly used spectrophotometric methods. Additive effect between protocatechuic acid and B vitamins were observed in DPPH assay, while synergistic effect is observed between caffeic acid and B3 vitamin. In CUPRAC and Folin-Ciocalteu assays only antagonistic effects were observed.