Chemical and biological characterization of Conyza dioscoridis (L.) desf. family (Compositae) in some perennial weeds control

• C. arvensis can be controlled by C. dioscoridis aqueous and organic extracts.
• The mixture of eudesmane derivatives, methyl 15-oxo-eudesome-4, 11(13)-diene 12-oate, 1α, 9α-dihydroxy-α-cyclocostunolide, isorhamnetin 3 -sulfate and isorhamnetin 3-O-rutinoside were the first time proven its phytotoxicity.
• Also, rhamanetin and epicatechin were the first time isolated from C. dioscoridis.

The potential herbicidal activity of certain chemicals isolated from Conyza dioscoridis (L.) desf. leaves was bioassayed on seed germination and growth parameters of Convolvulus arvensis (L.) and several weeds including Portulaca oleracea (L.), Phalaris paradoxa (L.), Corchorus olitorius (L.) and Echinochloa crus-galli (L.) Beauv. Bioassay guided isolation showed seven phytotoxic natural compounds including three sesquiterpene compounds. An inseparable mixture of the eudesmane derivatives (15-hydroxyisocostic acid and the corresponding aldehydic acid) was isolated from the leaves of C. dioscoridis. Relative to controls, this mixture reduced total biomass of C. arvensis by (86.81%) and methyl 15-oxo-eudesome-4, 11(13)-diene 12-oate as well as 1α, 9α-dihydroxy-α-cyclocostunolide showed 86.28% and 76.19% reductions respectively, compared to its control. Also, four flavonoids caused the reductions in C. arvensis total biomass fresh weight by: isorhamnetin 3-sulfate (80.61%), isorhamnetin 3-O-rutinoside (80.39%), rhamanetin (76.25%) and epicatechin (70.58%) compared to its control. The activity of these chemicals may be nominating them to develop as natural herbicides in the future.