Showing papers on "Phytoalexin published in 1971"

Phenolic compounds in relation to phytoalexin biosynthesis in hypocotyls of Phaseolus vulgaris

Abstract: The major phenolic compounds in Phaseolus vulgaris hypocotyls are flavonol glycosides, leucoanthocyanins and hydroxycinnamic acid derivatives. These appear to account for all the reactivity of extracts towards Folin's reagent, when allowance has been made for interfering compounds. Treatment of the hypocotyls with drops of mercuric chloride solution or a culture filtrate of Penicillium expansum causes the production of the phytoalexin phaseollin but only small changes in the levels of endogenous phenols. Coumestrol, a compound related to phaseollin, is produced at the same time. It is suggested that phytoalexin formation in P. vulgaris may represent a specific stimulation of isoflavonoid metabolism which is separate from any general increase in phenol metabolism associated with cell necrosis.

Nature of the phytoalexin produced by alfalfa in response to fungal infection

Abstract: A phytoalexin was isolated from alfalfa (Medicago sativa) leaves by the drop-diffusate technique using spore suspensions of Helminthosporium turcicum as inoculum. The phytoalexin was identified as (−)-3-hydroxy-9-methoxypterocarpan (demethylhomopterocarpin), a compound previously isolated from several tropical leguminous trees. The identification was made on the basis of the mass spectrum, proton magnetic resonance spectra of both the phytoalexin and its monoacetate, infrared and ultraviolet spectra and the physical constants.