EFFECTS OF CUCUMBER MOSAIC VIRUS AND ASTER YELLOWS PHYTOPLASMA (16SrI-B) ON THE QUALITY OF ECHINACEA PURPUREA ESSENTIAL OIL

Echinacea purpurea Moench (L.), known as purple coneflower, is one of the most important medicinal plants, used worldwide for its immunostimulant, bacteriostatic and anti-inflammatory properties, as natural drug and/or food supplement (as infusion). In a previous study carried out in 2002 in Italy to verify possible influence of viral infectious on the plant oil composition, the oil from plants (grown at the Herb Garden of Casola Valsenio, Emilia Romagna region) infected by Cucumber mosaic virus (CMV) was compared to the one from healthy plant by combined gas chromatography mass spectrometry (GC/MS) analyses. Significant quantitative variations in their compositions were verified; the infected materials afforded a lower content of sesquiterpene hydrocarbons (e.g., the percentage of germacrene D was reduced of 52%) (Hudaib et al., 2002). Considering that in 2009, E. purpurea plants cultivated in the same Herb Garden showing virescence flower symptoms, were found infected by a phytoplasma belonging to ribosomal subgroup 16SrI-B (Aster Yellows, ‘Candidatus Phytoplasma asteris’: AY) (Bellardi et al., 2009), the essential oils from CMV-infected, AY-infected, and healthy E. purpurea plants were investigated to confirm that other factors (in addition to origin, cultivation, environmental conditions), such as pathogen infections, may induce variations in the oil composition and quality. Before collection, each plant showing flower virescence, CMV symptoms (yellow mosaic on the leaves) and other asymptomatic ones (control), was labelled after visual inspection of the aerial parts and analyzed by PAS-ELISA, RT-PCR and SSCP (for CMV presence), PCR and RFLP (for AY presence). These diagnostic tests allowed the separation of three distinct batches of plant material (leaves and flowers): AY(16SrI-B)-infected, CMV(belonging to subgroup IA)-infected and healthy. Steam distillation was used to extract essential oil from dried aerial part using a commercial Clevenger apparatus. Identification of the compounds was made by GC/MS. A total of 30 compounds were identified and qualitative composition resulted comparable to that already reported; however the percentages of all compounds in the three oils were different. The main differences were detected for three components: limonene (2.2 % in healthy, 8.4% in CMV-infected, and 4.4% in AY-infected plants), cis-verbenol (1.8% in healthy, 3.4% in CMV-infected, and 5.6% in AY-infected plants), and its relative ketone verbenone (2.7% in healthy, 7.1% in CMV-infected, and 11.4% in AY-infected plants). Another minor increase was recorded for carvone (0.8 % to 2.5 %) content, but only in plants affected by phytoplasmas. These chemical differences in the oil composition can be useful to characterize the “product” whose pharmacological activity is frequently reported to correlate with its components. Considering the economic importance of E. purpurea as medicinal species, in addition to the routine growth-stage control during the plant life cycle, attention should be also paid to the plant health-status upon its collection, to ensure uniformity of the drug constituents and a better standardization of production procedures. Bibliography Bellardi M.G., Paltrinieri S., Contaldo N., Benni A., Bertaccini A.., Biffi S. Natural 1, 2009, 84, 24-31. Hudaib M., Cavrini V., Bellardi M.G., Rubies-Autonell C., J. Essent. Oil Res., 2002, 14, 427-430. Mazza G., Cotrell T. J. Agric. Food Chem. 1999, 47, 3081-3085 and reference cited herein.