Seasonal Variation of Essential Oils Composition in a Genetically Diverse Population of Lippia alba and Its Influence on Antibacterial Activity.

Lippia alba is an aromatic plant whose essential oils (EOs) have been characterized as promising antimicrobial agents. It has been established that L. alba chemotypes are influenced by both genetic and environmental factors. We evaluated the EO yield, composition, and antimicrobial activity of 20 genotypes from a sympatric genetically diverse population of L. alba. These analyses were performed over two seasonal periods, during which climate data were collected and leaf nutrients assessed. EO yield was highest on average during summer, although genotype-specific patterns were observed. Gas chromatography-mass spectrometry identified 47 compounds, which 27 were observed to be shared among the 20 genotypes. A total of 10 of the 20 genotypes studied had seasonal shifts in predominant constituents. Minimum inhibitory concentration (MIC) assays showed high antimicrobial activity in summer samples, followed by spring, despite being more effective in the first seasonal data. Micronutrients data suggest that nutrient variation may be associated with changes in essential oil composition. Though exploratory, these results highlight the importance of considering both genotype and harvest season for EO standardization in antimicrobial phytotherapy and other potential applications.