1 research outputs found
Phytotoxins from <i>Tithonia diversifolia</i>
<i>Tithonia diversifolia</i> (Mexican sunflower) is a
dominant plant of the Asteraceae family, which suggests it produces
allelochemicals that interfere with the development of surrounding
plants. The study described herein was conducted to identify the compounds
that have phytotoxic activity in <i>T. diversifolia</i> extracts.
Ethyl acetate extracts of the leaves, stems, and roots showed significant
inhibition of wheat coleoptile growth, and the leaf extract had similar
inhibitory effects to a commercial herbicide. Fourteen compounds,
12 of which were sesquiterpene lactones, have been isolated. Two sesquiterpene
lactones are reported for the first time and were isolated as an inseparable
mixture of 8β-<i>O</i>-(2-methylbutyroyl)tirotundin
(<b>4</b>) and 8β-<i>O</i>-(isovaleroyl)tirotundin
(<b>5</b>). Their structures were determined by spectroscopic
analysis, including NMR techniques and mass spectrometry. The sesquiterpene
lactones 1β-methoxydiversifolin (<b>6</b>), tagitinin
A (<b>7</b>), and tagitinin C (<b>8</b>) were the major
products identified. These compounds were active on etiolated wheat
coleoptiles, seed germination, and the growth of STS and weeds. The
phytotoxic activity shown by these sesquiterpene lactones indicates
that they are the compounds responsible for the activity exhibited
by the initial extracts