Exploring the anti-alpha-amylase activity of flavonoid aglycones in fabaceae plant extracts: a combined MALDI-TOF-MS and LC-MS/MS approach

A combination of TLC-bioautography, MALDI-TOF-MS and LC-MS/MS methods was used to identify flavonoids with anti-alpha-amylase activity in extracts of Lathyrus pratensis L. (herb), L. polyphillus L. (fruits), Thermopsis lanceolata R. Br. (herb) and S. japonica L. (buds). After the TLC-autobiography assay, substances with anti-amylase activity were identified by MALDI-TOF-MS followed by confirmation of the result by LC-MS/MS. Results of the study revealed that the flavonoids apigenin, luteolin, formononetin, genistein and kaempferol display marked anti-alpha-amylase activity. Formononetin showed the largest activity. Compared with LC-MS/MS, MALDI-TOF-MS is a quick and convenient method; results can be obtained within minutes; and only minor sample amounts are required which allows us to analyse mixtures of substances without preliminary separation. However, the inability to distinguish between isomers is the main limitation of the method.