Effect of Growing Locations on the Essential Oil Content and Compositions of Lemon Verbena Shrubs under the Conditions of Egypt

Abstract

The essential oil of lemon verbena Lippia citriodora L. leaves (family Verbenaceae) was evaluated as a new source of essential oil under Egyptian conditions. The leaves of Lippia citriodora, shrubs growing in the Delta Nile and Upper region of Egypt were collected monthly (during a 5-month interval) in order to follow plant development and essential oil composition. The conditions of Delta Nile (Qalyupia) location were favorable in comparison to Upper Egypt (Giza) location since, the high values of plant height, number of branches / plant, leaf area and fresh and dry yield of leaves and twigs were recorded for Qalyupia plants compared with Giza location. At the same time Plants at Qalyupia location produced the heaviest fresh weight of leaves and twigs compared with Giza location. The data indicated that, there was gradual marked decrease in the oil percentage with the increase growth rate of leaves and twigs. Also comparing the results at the top oil yield production in two locations, the plants of Qalyupia location gave the highest yield of oil compared with Giza location. Studies on the chemical compositions of the essential oil of Lemon verbena have been undertaken. The essential oils extracted from leaves and twigs were estimated during the growing season by means of GC, GC-MS. Twenty five compounds were identified in the oil of two locations, they represent approximately 79.0 % and 81.2 % for Giza and Qalyupia oil respectively. The main components of essential oil were Limonene (16.4 % and 15.4 %), Citral ( 15.0% and 13.0 %), Neral (11.3% and 10.3%) and 1,8-Cineole (7.5 % and 9.6%) produced under Nile Delta and Upper Egypt respectively. On the other hand, the changes in the essential oil content (quantity and composition) varied, according to corresponding environmental and growth factors, periodic increase and decrease in their concentrations was observed. The total main constituent percentage varied from 37.8 % in July harvest to 47.6 % in October harvest under Qalyupia location. The lowest value of the total main constituents was found with August harvest under Giza locations (36.8 %)