4',7-Dihydroxyflavone

4',7-Dihydroxyflavone can induce transcription of nodulation (nod) genes in Rhizobium meliloti. It has inhibitory activities against COX-2.Root exudate from 3-day-old alfalfa seedlings was purified and then assayed for biological activity with a nodABC-lacZ fusion in R. meliloti. Indentities of major nod inducers were established by spectroscopic analyses (ultraviolet/visible, proton nuclear magnetic resonance, and mass spectroscopy) and comparison with authentic standards. Major nod inducers, which were identified as 4',7-Dihydroxyflavone, 4'-7-dihydroxyflavanone, and 4,4'-dihydroxy-2'-methoxychalcone, were released from seedling roots at 54, 22, and 20 picomole.plant (-1) .day (-1), respectively. Luteolin was not found in these root exudates.