Chemical Composition and Allelopathic Activity of Parthenium hysterophorus and Ambrosia polystachya Weeds Essential Oils

Abstract

The volatile constituents of the essential oils from leaves from the weed plants Parthenium hyste-rophorus and Ambrosia polystachya were identified and quantified by GLC-MS and GLC. Allelo-pathic activities were determined by methods that evaluated the volatile effects and the direct ap-plication of these essential oils on the seed germination and seedling vigor of lettuce. We identi-fied 27 compounds in the essential oil from P. hysterophorus, and the main constituents were germacrene-D (35.9%), trans-β-ocimene (8.5%) and β-myrcene (7.6%). In the essential oil from A. polystachya, 40 constituents were identified and the principal compounds were germacrene-D (29.3%), trans-β-ocimene (13.6%) and β-caryophyllene (9.8%). In both methods, the essential oil from A. polystachya presented a greater potential for reducing seed germination and seedling vi-gor in lettuce than the essential oil from P. hysterophorus, and this activity might be attributed to its higher content of monoterpenes.