Harvest time and geographical origin affect the essential oil of Lippia gracilis Schauer

Abstract Lippia gracilis Schauer (Verbenaceae) is a promising shrubby aromatic species for the production and marketing of essential oils rich in thymol and carvacrol. The aim of this study was to evaluate the effect of harvest time and geographical origin on the essential oil of L. gracilis accessions. We tested the accessions LGRA106, LGRA107, LGRA108, LGRA109, LGRA110, LGRA201 and LGRA202, harvested in 2009 and 2012. The essential oils were extracted by hydrodistillation using a modified Clevenger apparatus. The chemical components were identified by gas chromatography coupled with mass spectrometry and flame ionization detection (GC/MS-FID). The essential oil contents of L. gracilis exhibited significant variation among accessions only in four-year-old plants. Accession LGRA202 had the highest essential oil content (4.66%), whereas the lowest content was recorded for accession LGRA107 (2.35%). When compared among harvest times, higher contents of essential oils were found in four-year-old plants. The largest variation was observed in accession LGRA202 plants, whose contents increased from 1.52% in one-year-old plants to 4.66% in four-year-old plants. In the two assessed harvest times, carvacrol was the major compound, except in accession LGRA106, whose major compound was thymol. Harvest time reduced the content of the major compound (carvacrol or thymol) of the essential oils from all accessions. Accession LGRA202 exhibited the largest reduction in carvacrol content, from 47.29% in one-year-old plants to 34.29% in four-year-old plants. The accessions exhibit chemical variability in the major compounds carvacrol or thymol. Harvest time and geographical origin affected the content and proportion of chemical constituents of essential oils of all L. gracilis accessions.