Bioactive flavonoids from Helianthus annuus cultivars

Isolation, structure elucidation and allelopathic bioassay of five flavonoids (the flavonol tambulin, the chalcones kukulcanin B and heliannone A, and the flavanones heliannones B and C) from the sunflower cultivar VYP(R) are described. Heliannones A-C are reported in the literature as natural products, for the first time. The effects of a series of aqueous solutions at 10(-4)-10(-9) M of the flavonoids on the root and shoot length of Lycopersicon esculentum and Hordeum vulgare has been studied. They influence, principally, the shoot growth of seedlings, but germination and radical length can be affected by chalcones. The effects of very similar compounds, kukulcanin B and heliannone A, varied. The reason for this variation could be related to the number and position of free hydroxy groups. (C) 1977 Published by Elsevier Science Ltd.