Evaluation of the allelopathic potential of root exudates of Cosmos sulphureus (Cav)

Abstract

Cosmos sulphureus Cav. is a species that was introduced in Brazil as an ornamental plant due to the exuberance of its yellow-orange flowers and currently behaves as a weed due to its high propagating and spreading potential. In an exploratory work performed by LAPDA, 26 compounds were isolated from leaves and roots, and four of them were described for the first time, being the major compounds of the leaf extract the sesquiterpene lactones costunolide, reynosin and santamarin, and these showed inhibition of Amaranthus viridis and Panicum maximum. Therefore, the objective is to study the allelopathic potential of root exudates of C. sulphureus, aiming to find models of "Natural Herbicides", more specific and innocuous, that help the integral protection of the environment and that allow to assist in the management of weeds, rationalizing it and making it less impactful to the environment. To this end, two experiments will be developed. In the first, the allelopathic potential of C. sulphureus will be characterized by root exudation (plant "in vivo" at three stages of development) by hydroponics and in the second by the method of inverted bottles. From the collected exudates, the salts of the nutritive solution will be eliminated, obtaining two fractions (acetone and methanol). The methanolic fraction will be used in bioassays (cytotoxicity and phytotoxicity) with A. viridis, P. maximum and Lactuca sativa as test plants. Then, the methanolic fraction will be isolated and purified by thin layer chromatography (FLC) and/or 'Dry Flash' column (DC) and/or HPLC, and the fractions or isolated compounds will be used in bioassays (cytotoxicity and phytotoxicity). The most active compounds will be identified by means of proton (1H-MRN) and carbon (13C-MRN) nuclear magnetic resonance, combined with correlated (1H - 1H COSY) and heteronuclear correlated (1H - 13C HETCOR) spectroscopy and mass spectrum (MS).