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

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.