Accumulation and composition of essential oil due to plant development and organs in wormwood (Artemisia absinthium L.)

The accumulation of essential oil of wormwood is influenced by various biological factors. A study was conducted to determine factors influencing the content and composition of volatiles in Artemisia absinthium L. due to ontogenesis and organic differentiation. Thujone (T) and trans-sabinyl-acetate (SA) chemotypes were harvested in 2017 at the vegetative, budding, flowering and after-flowering phases; flowers and leaves were sampled separately. Results show that regardless of phenophase, the essential oil (EO) content of flowers is always higher than the leaves, and the differences between them are larger from 0.31 mL/100 g (after flowering stage) to 0.91 mL/100 g (flowering stage) in SA. While the plant is developing, the accumulation level decreases in both flowers and leaves. The qualitative composition of flower and leaf EO is similar, with the exception of two compounds in T and five compounds in SA, which appear only in the flowers. The main compounds (alpha-thujone and beta-thujone) in T showed random fluctuations, while trans-sabinyl-acetate, the major component in SA, tended to decrease. An accumulation pattern with peak values at flowering in both organs was registered for selinene in T and selin-11-en-4-alpha-ol in SA. Similar accumulation dynamics were determined for another 6 compounds in T and for 4 compounds in SA but only in the flowers. The overall ratio of monoterpenes is much higher than that of the sesquiterpenes in both leaves and flowers of both chemotypes. During plant development, the ratio of monoterpenes fluctuated in T while in SA, it decreased, with the lowest values detected after the flowering phase. The study confirmed the compositional changes during plant development are primarily quantitative but revealed that the tendencies of these changes are various between two investigated wormwood chemotypes.