Dagne Ermias (Professor)Gizachew Zelalem2019-11-042023-11-092019-11-042023-11-092019-03-01http://etd.aau.edu.et/handle/12345678/19778Weeds are plants growing in agriculture areas where they are not wanted and gravely affect the agriculture sector more than other crop pests. Parthenium hysterophorus (Kinche arem in Amharic) is one of the worst invasive weeds in the world. It is poisonous to germination and growth of crops. It is estimated that this weed decreases the production of crops by more than 25%. To date attempts to control the spread of this weed by synthetic chemicals have not been successful. Allelopathic plants produce natural chemicals that inhibit growth of weeds. In this project we have screened several plant extracts and purified compounds in order to find substances that may be used to combat the spread of the above weed. In this project we have tested several plant extracts to study their effect on the growth of the above weed. We discovered that the ethanol extracts of Echinops kebericho root, Warburgia ugandensis bark, aerial parts of Solanecio gigas, Achyranthes aspera and Premna schimperi completely inhibited Parthenium seed germination at a dose of 0.05 mg/mL. Using bioassay-guided protocol; dehydrocostus lactone (28) isolated from the root of E. kebericho was found to be the most active. Muzigadial (48) and cinnamolide-3β-acetate (64) from W. ugandensis bark were also very active. In the course, albicanyl acetate (115) and caseamemin (117) were isolated for the first time from this plant species with other known compounds like ugandensidial (60), polygodial (49), 9-deoxymuzigadial (116), and 11α-hydroxymuzigadiolide (66) with moderate phytotoxic activities. Other compounds with intermediate activities were also isolated from A. aspera (stigmasterol glycoside (82) and P. schimperi (kaempferide (112)). CHOCHOOHH48CHOHCHOH49OOHOOH66CHOOAcCHOOH60OOAcO64CHOCHO116enPlant DerivedCompounds Against the Widespread WeedParthenium HysterophorusThesis