Lippia alba is a native species popularly known as "lemon balm", used in folk medicine for the treatment of several diseases. This work aims to study the ethnobotany of L. alba and to determine the chemical composition of essential oils from the fresh leaves of L. alba during both rainy and dry seasons. The volatile contents of the oil samples were determined by Gas Chromatography coupled to Mass Spectrometry - GC/MS. The chemical composition of the samples was determined by comparing the experimentally observed retention indices with those of the literature database, as well as by comparing the mass spectra with the equipmentâ€™s database. The yield of the oils ranged from 0.070 to 0.628%, where the highest yields were observed with the dry season samples. The essential oils were composed of monoterpenoids and sesquiterpenoids. Citral (42.32 - 80.69%) and geraniol (3.85 - 16.65%) were the major constituents in eight of the nine samples analyzed. The highest content of citral was achieved when L. alba was leaves were collected at 14:00 PM. Due to the high variability in the chemical composition of the essential oil of L. alba, the genotypes were grouped into chemotypes, where it was verified that this species belongs to the citral-geraniol chemotype. Since all samples were grown in the same environment, the observed variation in the content and composition of the essential oil seem to be due to the time (8:00 AM versus 14:00 PM) and season by which the L. alba leaves were collected.
Keywords: Lippia alba; Essential oil; Phytotherapy; Chemical characterization