Synthesis of flavonol-bearing probes and chemical proteomic analysis of Asteraceae petals in search of flavonoid enzymes

In flowers of Asteraceae, yellow flavonols bearing an additional hydroxyl group at positions 6 or 8 (ring A) contribute to petal UV-absorbing pigmentation patterns, which play a crucial role in attracting pollinating insects. Understanding the biogenesis of these special flavonols requires the identification of any specific enzyme involved in these incorporations of extra hydroxyl groups on the quercetin ring A. To this aim, flavonol-bearing biotinylated probes have been designed and synthesized to explore their ability to selectively capture target proteins or biosynthetic enzymes under oxidative activation. These probes demonstrate the ability to capture several flavonoid enzymes from Rudbeckia and Tagetes microsomes and allow the identification of uncharacterized candidates for novel flavonoid enzymes.