Kazuomi Yasui

A species-selective allelopathic substance from germinating sunflower (Helianthus annuus L.) seeds

From the exudate of germinating sunflower (Helianthus annuus L.) seeds was isolated a stereoisomer of diversifolide, 4, 15-dinor-3-hydroxy-1(5)-xanthene-12,8-olide (designated sundiversifolide) as determined by analysis of its IR, APCI-, ESI- and HR-MS and 13C and 1H NMR spectra. This substance inhibited shoot and root growth of cats-eyes by about 50% at a concentration of 30 ppm. It also showed species-selective activity on the shoot and root growth of tested plants. When cats-eyes seeds were incubated together with sunflower seeds, the cats-eyes growth was inhibited. Furthermore, it was detected from an extract of river sand when sunflower seeds were incubated on the sand. These results indicate that sundiversifolide has an allelopathic function in sunflower plants.