POTENTIAL ALLELOPATHIC GUAIANOLIDES FROM CULTIVAR SUNFLOWER LEAVES, VAR SH-222

The leaf aqueous extracts of cultivar sunflower (Helianthus annuus L.) var. SH-222(R) afforded, from the medium polar fractions, five new guaianolides, the annuolides A-E which have been tested as allelochemicals. Their structures and stereochemistry were elucidated by spectroscopic analysis. A series of aqueous solutions at 10(-4)-10(-9) M of annuolides A-E were tested for their effects on the germination and growth of the dicotyledon Lactuca sativa and the monocotyledon Hordeum vulgare species. All five guaianolides posses potential allelopathic activity, in particular over dicotyledon species, and are likely to be significantly involved in the allelopathic action of cultivar sunflowers.