Analysis of flavonoids from red clover by liquid chromatography electrospray mass spectrometry

A high-performance liquid chromatographic method paired with photodiode-array and electrospray mass spectrometer detectors enables us to rapidly characterize the flavonoid constituents from red clover. A total of eleven flavonoids were identified. Among them, seven flavonoids - genistin, isoquercitrin, ononin, daidzein, sissotrin, formononetin and biochanin A-were unambiguously identified based on their abundant [M+H](+), [M+Na](+) ions, UV spectra, retention time and analysis of hydrolyzed products. The purity of three peaks, for pratensein, pectolinarigenin and pseudobaptigenin, is not enough to have predominant [M+H](+) or [M+Na](+) ions, but their existence is believable. Hyperoside has intense [M+H](+) and [M+Na](+) ions. Its identification is still tentative, because there are several other quercetin glycosides which will have the same [M+H](+) ion.