HS-SPME method to monitoring „in vivo“ volatile compounds emitted from Achillea collina infested by aphids

Plant leaves normally release small quantities of volatile compounds, but when it is damaged by herbivorous insects, many more volatiles are produced. The emitted volatile fraction plays a key role in plant-environment interaction, being involved in important processes in plant life cycle [1]. Determination of volatile compounds release from living plants are usually performed by enclosing the whole plants or some of its parts in glass o plastic chambers, followed by collection of the emitted compounds in sorbent traps and chromatographic analysis of the adsorbed compounds. This general procedure has some drawbacks for example some material employed as trapping can introduced artifact. This work describes the application of an Headspace Solid Phase Micro-Extraction (HS-SPME) and Gas-Chromatographic Mass-Spectrometric (GC-MS) method to characterize the volatile compounds emitted by leaving leaves of Achillea collina Becker ex Rchb, infested by aphids (Macrosifonella) using a sampling glass chamber specially designed for this task. In particular, the headspaces volatiles were extracted using a divinylbenzene-carboxen-polydimethylsiloxane (DVB/CAR/PDMS, 70/30µm) fiber. The extraction conditions including extraction temperature and time were also optimized using the total peak area as index. The best response was obtained at room temperature for 240min. As a result, many volatile compounds appeared as new compounds after infestation (α-fenchene, aromadendrene and pinocarvone). Other compounds showed an increase trend after infestation by aphid such as camazulene, followed by β-pinene, α-bergamotene and β-phellandrene. In conclusion, the present method is simple and effective and can be used to study the „in vivo“ volatile compound emissions from medicinal plants.

References: 1. Pareja M. et al. (2007). J Chem Ecol 33: 695–710.