LC-ESI-MS study of the flavonoid glycoside malonates of red clover (Trifolium pratense)

High-performance liquid chromatography-electrospray ionization-mass spectro metry (LC-EST-MS) was applied to the analysis of the flavonoids and their g lycoside malonates of the flowers and leaves of red clover (Trifolium prate nse). Through LC-MS comparative studies on the plant extracts and their mal onate-free extracts, similar to 20 flavonoid glycoside malonates were detec ted in the flower extract. Eight were identified as genistin 6"-O-malonate (39), formononetin 7-O-beta-D-glucoside 6"-O-malonate (40), biochanin A 7-O -beta-o-glucoside 6"-O-malonate (41), trifoside 6"-O-malonate 42, irilone b eta-D-glucoside 6"-O-malonate (43), pratensein 7-O-beta-D-glucoside 6"-O-ma lonate (44), isoquercitrin 6"-O-malonate (45), and 3-methylquercetin 7-O-be ta-D-glucoside 6"-O-malonate (46). About 15 other flavonoids and clovamides were proved to be present in this extract. The study also found that the f lowers contained flavones as the major flavonoids, whereas the leaves had i soflavones as the major flavonoids. This is the first detection of the six malonates (39 and 42-46) in the extracts of red clover, and among them, 42, 43, and 46 are new compounds.