New C-4''-Hydroxy Derivatives of Maysin and 3'-Methoxymaysin Isolated from Corn Silks (Zea mays)

Reduced derivatives of maysin [2"-O-alpha-L-rhamnosyl-6-C-(6-deoxy xylohexos-4-ulosyl)luteolin] and 3'-methoxymaysin have been isolated and identified from several corn (Zea mays L.) inbreds. These include 2"-O-alpha-L-rhamnosyl-6-C quinovosylluteolin (equatorial 4"-OH-maysin, eq-4"-OH-maysin), 2"-O-alpha-L-rhamnosyl-6-C-fucosyllute olin (axial 4"-OH-maysin, ax-4"-OH-maysin), and 2"-O-alpha-L-rhamnosyl-6-C-fucosyl-3' methoxyluteolin (ax-4"-OH-3' methoxymaysin). In addition to maysin and 3'-methoxymaysin, inbred Tx501 contains minor amounts of ax-4"-OH-maysin and ax-4"-OH-3'-methoxymaysin. Corn lines A103, GE275, ESDJ1, and CML131 contained relatively large levels of both ax-4"-OH-maysin and eq-4"-OH-maysin. Synthetic 4"-OH-maysin (obtained by NaBH4 reduction of maysin) was tested for growth inhibition of corn earworm (Helicoverpa zea Boddie) larvae in a laboratory bioassay and found to be almost as active as maysin, suggesting that incorporation by breeders of these compounds into silks could enhance the resistance of corn to corn earworm larvae