The potential of Cosmos sulphureus Cav. extracts as a natural herbicides

The secondary metabolites of Cosmos sulphureus Cav. are dominated by phenolic acids which functioned as allelochemicals. This research aimed to determine C. sulphureus. extracts effects and the optimum concentration on soybean germination and early seedling growth. C. sulphureus root, stem, leaf and flower aqueous extracts were assayed at 1, 5, and 10% and total phenols were quantified. Results showed aqueous extracts from all organs and all concentrations inhibited soybean seed germination and seedling growth. The degree of inhibition correlated positively to extract concentrations. Toxicity of C. sulphureus extracts varied based on plant part and was related to phenolic acid content, with toxicity by flower demonstrating the highest toxicity followed by leaf, stem and root. The flower extract had the highest phenolic acid content (14.96%). Further works intended to specify and verify the allelochemicals produced by this plant are still required.