Production, transformation and essential oils composition of leaves and stems of lemon verbena [Aloysia triphylla (L’Herit.) Britton] grown in Portugal

Production, transformation and essential oils composition of leaves and stems of lemon verbena [Aloysia triphylla (L’Herit.) Britton] grown in Portugal. More than seventy compounds, including 13 n-alkanes, were identified by GC and GC-MS in essential oils from leaves of lemon verbena [Aloysia triphylla (L’Herit.) Britton] plants harvested and analysed with intervals of around two months during a year. In essential oils from stems of corresponding samples, a lower number of compounds were detected, ranging from 46 to 52 depending of the sample. In both cases, geranial, neral and limonene were the main compounds accounting together for 69-72% and 53-69% of the essential oils from leaves and stems respectively. The variation of the essential oil composition in stems was broader than in leaves. In stems, the levels of geranial decreased from around 40% in Sep. to 27% in Nov., increasing thereafter, in inverse correlation with the levels of caryophyllene oxide and ARcurcumene. In stems, the level of α-terpineol increased from 1.3% in July to 3.4% in April of the following year while that of methyl citronelate increased from 0.5% in July to 2.9% in Nov. In leaves, the levels of α-terpineol and methyl citronelate kept without apparent variation. In stems, either the variation of the monoterpene hydrocarbons or the variation of the sesquiterpene hydrocarbons was inversed relatively to respective variations in leaves. Limonene and E-ß-ocimene were the compounds that mostly contributed for variation of monoterpene hydrocarbons while E-caryophyllene, germacrene D, α-zingiberene and AR-curcumene were those that mostly contributed for variation of sesquiterpene hydrocarbons.