Geographic location and seasonality affect the chemical composition of essential oils of Lippia alba accessions

Abstract

The chemical composition of essential oils (EO) is determined by genetic factors; however, these factors strongly interact with the environment, leading to significant changes in their constitution. The aim of this study was to evaluate the effect of geographic location on the chemical composition of the EO of seven accessions of Lippia alba (LA-03, LA-13, LA-24, LA-32, LA-36, LA-57, and LA-59) harvested monthly. Trails were conducted simultaneously in São Cristóvão, State of Sergipe, and Uberlândia, State of Minas Gerais, Brazil, from August 2017 to July 2018. The EO obtained by microwave-assisted distillation were analyzed by GC/MS-FID. In cluster analysis, it was observed that for all months, two groups were formed in each location. In Uberlândia, Group 1, with greater abundance of geranial + neral + linalool, included LA-03, LA-24, LA-32, LA-36, and LA-59; and Group 2, with greater abundance of carvone, included LA-13 and LA-57. The same response was observed in São Cristóvão, except for accession LA-24 in August, October, January, February, June, and July, which migrated from Group 1 to Group 2, joining LA-13 and LA-57. There were significant differences in the concentrations of the principal compounds between the locations. Greater concentrations of neral, 1,8-cineole, and ρ-cymene were obtained in accessions LA-03 (38.40%), LA-57 (11.50%), and LA-32 (7.97%), respectively, harvested in Uberlândia. Greater concentrations of carvone (75.66%), linalool (68.19%), geranial (55.90%), limonene (12.18%), piperitone (9.68%), and caryophyllene oxide (6.69%) were obtained in accessions LA-57, LA-24, LA-59, LA-57, LA-13, and LA-59, respectively, harvested in São Cristóvão. There were significant differences in the concentrations of the main compounds, showing that the chemical profiles of the essential oils of L. alba accessions are affected in a quantitative and qualitative way, both between harvests of monthly leaf regrowth in the same geographic region, and in harvests performed in different regions. These data reinforce the need for standardization of essential oil production in native perennial plants, for greater stability of the compounds.