Tithonia diversifolia (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 T. diversifolia 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-O-(2-methylbutyroyl)tirotundin (4) and 8β-O-(isovaleroyl)tirotundin (5). Their structures were determined by spectroscopic analysis, including NMR techniques and mass spectrometry. The sesquiterpene lactones 1β-methoxydiversifolin (6), tagitinin A (7), and tagitinin C (8) were the major products identified. These compoun...

/pdf/phytotoxins-from-tithonia-diversifolia-2gr8v16l3p.pdf

Phytotoxins from Tithonia diversifolia.

The allelopathic effects of fresh shoot aqueous extract of Tithonia diversifolia(Hemsl.) A. Gray was investigated on the germination of seeds and growth of young seedlings of Zea mays L. Although the fresh shoot aqueous extract did not show significant allelopathic effect on the germination of Z. mays, however, the radicle and plumule lengths of the seedlings were significantly inhibited by the fresh shoot aqueous extract. Also, the fresh shoot aqueous extract of T. diversifolia was found to significantly stimulate the growth of older plants of two weeks old and above. The application of fresh shoot aqueous extract of T. diversifolia was observed to significantly enhance the following growth parameters: fresh weight, dry weight, leaf area and ratio. In addition, chlorophyll a, chlorophyll b and total chlorophyll accumulation were reduced in these young plants. The study was able to reveal that fresh shoot aqueous extract of T. diversifolia could have differing effects (inhibitory and stimulatory), on seedling growth of this test crop, depending on plants growth stage.

	 

	Key words: Allelochemicals, allelopathy, fresh shoot aqueous extract, inhibitory, stimulatory, Tithonia diversifolia, Zea mays.

https://www.academicjournals.org/article/article1380635018_Oyerinde et al..pdf

Allelopathic effect of Tithonia diversifolia on the germination, growth and chlorophyll contents of maize (Zea mays L.).

The search for sustainable alternatives to synthetic herbicides for weed control, has led the scientific community to an increased interest for plant allelopathic mechanisms. The utilisation of plant extracts as possible bioherbicides represents an important solution. In the present study, laboratory experiments were carried out to investigate, for the first time, the differences in the allelopathic activity of the three Cynara cardunculus L. botanical varieties (globe artichoke, cultivated and wild cardoon) leaf aqueous extracts on the seedling growth of Amaranthus retroflexus L. and Portulaca oleracea L. In addition, the autoallelopathic effect on wild cardoon growth and the qualitative profile of the aqueous extract through high-performance liquid chromatograpy (HPLC) analysis were evaluated. Overall, the allelopathic effects were both genotype- and weed species-dependent. Wild cardoon showed the highest allelopathic potential (–23.4%), followed by cultivated cardoon and globe artichoke, and P. oleracea was the most sensitive target species (–32%). Besides, root system length was the most affected parameter (–32.6%). The autoallelopathic effect of wild cardoon extract was also demonstrated on root system length, hypocotyl and epicotyl length and total dry weight. C. cardunculus leaf aqueous extract was characterised by 5 sesquiterpene lactones, 2 caffeoylquinic acids, 6 flavones and 1 lignan. From the HPLC analysis we found that apigenin and luteolin 7-Oglucoronide were detected only in wild cardoon, apigenin 7-Oglucoside was typic of globe artichoke, and 11,13-dihydro-deacylcynaropicrin and 11,13-dihydroxi-8-deoxygrosheimin were characteristics of cultivated cardoon.

Allelopathic potential of leaf aqueous extracts from Cynara cardunculus L. on the seedling growth of two cosmopolitan weed species

Investigation was carried out on the phytochemical composition of methanolic and water aqueous extracts of Tithonia diversifolia and their phytotoxic effect on the growth of Sorghum bicolor (L.) Moench. The phytochemical analyses indicated the presence of bioactive substances such as alkaloids, saponins, glycosides, flavonoid, tannins, terpenoid and phenols in the methanolic extract and the later five allelochemicals in the water extract. The allelochemicals were of higher concentrations in the methanolic extract than in the water extract. The methanolic extract was found to be more phytotoxic than the water extract since the reduction of the germination percentage of the test crop was in the order of 100% methanolic extract > 50% methanolic extract >100% water extract. The germination and seedling growth inhibition was then extract concentration dependent and significant at P < 0.05. Both methanolic and water extracts have greater inhibitory effects on the growth of the radicle than on the plumule growth at 100% extract concentrations.

/pdf/phytochemical-screening-and-the-phytotoxic-effects-of-206bulizji.pdf

Phytochemical Screening and the Phytotoxic Effects of Aqueous Extracts of Tithonia diversifolia (Hemsl) A. Gray

Background:  Many alien plant species, such as  Tithonia diversifolia, T. rotundifolia  and  T. tubaeformis , have been introduced to areas outside of their natural distribution range to provide benefits, but have subsequently become invasive, threatening biodiversity and agricultural productivity. Objectives:  The aim of this study was to determine the current distribution and dates of introduction of invasive  Tithonia  species in eastern and southern Africa and to document the effects of  T. diversifolia  on rural livelihoods in Zambia. Method:  Roadside surveys, and other sources of information, were used to determine the distribution of invasive  Tithonia  species in eastern and southern Africa. Household interviews were conducted to gauge perceptions and understand the impacts of  T. diversifolia  on local livelihoods in Zambia’s Copperbelt province. Results: Tithonia diversifolia  is widespread in Uganda, Kenya, Tanzania, South Africa, Malawi and parts of Zambia but less so in Zimbabwe.  Tithonia rotundifolia  was comparatively uncommon in eastern Africa but common in some southern African countries, while  T. tubaeformis  was invasive in Swaziland, South Africa, Zambia and possibly also Zimbabwe. According to the majority of respondents in Zambia,  T. diversifolia  has negative impacts on native vegetation, mobility or access, water availability, crop yields and animal health. Conclusion:  Invasive  Tithonia  species are widespread and spreading throughout much of Africa. Livelihood and biodiversity costs have not been considered by those actively promoting the use and further dissemination of  T. diversifolia . We therefore recommend that detailed cost–benefit studies should be undertaken to support informed decisions on the future management of these species.

/pdf/distribution-of-invasive-alien-tithonia-asteraceae-species-3l46x8swun.pdf

Distribution of invasive alien Tithonia (Asteraceae) species in eastern and southern Africa and the socio-ecological impacts of T. diversifolia in Zambia

Allelopathic effects of Tithonia diversifolia (Hemsl) A. Gray on germination and growth of Amaranthus cruentus.

Phytotoxic effects of Tithonia diversifolia on germination and growth of Oryza sativa.

Allelopathic activities of some weeds in the Asteraceae family.

Effect of Chromolaena odorata on the Growth and Biomass Accumulation of Celosia argentea

Physiological response of Amaranthus cruentus and Oiyza sativa to phytotoxins of Tithonia diversifolia.

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