Effects of different harvest periods on essential oil components of Lippia citriodora Kunth under semi-arid climatic conditions and biological activities of its essential oil

Lemon verbena is cultivated mainly due to the lemon-like aroma emitted from its leaves that are utilized for most purposes. The chemical composition of the essential oil of lemon verbena was analyzed by GC/MS in July at pre flowering, in September at full flowering and in end of October at post flowering period. The in vitro antimicrobial activity of the essential oil, extracted from Lippia citriodora was tested against laboratory control strains belonging to the American Type Culture Collection (Maryland, USA) four Gram (+) and Gram (-) bacteria using the disc diffusion test. Antioxidant activity of the sample was determined by 1,1-diphenil-2- -picrly-hydrazil (DPPH) assay. Well-known antioxidant compounds such as ascorbic acid and α-tocopherol were used as standard. Results showed, among different harvest periods high fresh and dry herbage and dry leaf yields per plant were obtained from full flowering stage. Harvest periods were found to have a significant effect on the content of essential oil and the highest amounts of limonene, neral and geranial and measured as 31.15, 11.92 and 15.53%, respectively at full flowering stage. In all samples, the main constituents were limonene, neral and geranial constituting 46.03%–58.59% of the total essential oil yield depend on development stages. Lemon verbena essential oil was found to have antibacterial activity especially against Gram (+) microorganisms. In DPPH system, the moderate radical scavenging activity was exhibited. Therefore, L. citriodora has potential to be used as a natural antioxidant and antimicrobial agent in food processing.