Profiling and Quantification of Isoflavonoids in Kudzu Dietary Supplements by High-Performance Liquid Chromatography and Electrospray Ionization Tandem Mass Spectrometry

TLDR

Kudzu vine (Pueraria sp.) is a rich source of isoflavones, and dietary supplements derived from it are commercially available. The study aimed to detect and characterize isoflavonoids in kudzu dietary supplements using liquid chromatography coupled with negative and positive electrospray ionization tandem mass spectrometry and diode array detection. The authors employed LC‑MS/MS with both ionization modes and DAD, and quantified isoflavonoid concentrations by DAD‑HPLC. MS‑MS analysis revealed characteristic product ions for puerarin and daidzin, identified diagnostic ions for C‑glycosides, enabled neutral‑loss scans to propose structures of additional glycosides, and showed puerarin to be the most abundant component (8.44–30.60 mg/capsule) in commercial supplements.

Abstract

The kudzu vine (Pueraria sp.) is a rich source of isoflavones. Dietary supplements based on kudzu have become commercially available. In the present study, liquid chromatography coupled with negative and positive electrospray ionization tandem mass spectrometry (MS/MS) and diode array detection (DAD) has been used for the detection and characterization of isoflavonoids in kudzu dietary supplements (KDS). The MS/MS spectrum of the protonated ion of puerarin showed characteristic product ions of the C-glycoside unit itself, whereas daidzin generated an abundant Y(0)(+) aglycon ion in its product ion spectrum. A base peak due to the loss of 120 Da [M + H - 120](+) is the diagnostic ion for C-glycosides. Neutral loss scans allowed for the detection of other C- and O-glycosides in the methanolic extract of KDS, and their structures have been proposed. The concentration of isoflavonoids in the methanolic extract of commercially available KDS was quantified by using DAD-HPLC. Puerarin, rather than daidzin, was the most abundant component (8.44-30.60 mg/capsule) in commercially available KDS.