Characterization and yield evaluation of essential oils from different Tagetes species

Six species of Tagetes (T. erecta, T. filifolia, T. lucida, T. minuta, T. patula and T. tenuifolia), grown in northern Italy, were evaluated for their morpho-phenological characteristics, biomass yield and essential oil composition. The species showed marked differences in plant height, shape, flower size, habit and vegetative cycle length as found for T. filifolia which finished the vegetative cycle without reaching the flowering stage. The leaves always showed fresh material yields many fold higher than flowers (on average 26.8 and 4.4 t ha,(-1) respectively). Tagetes erecta and T. patula produced significantly higher amounts of flowers than the other species (7.3 and 6.4 t ha,(-1) respectively), whereas Tagetes lucida and T. filifolia were those with the highest yields of leaves (41.9 and 33.3 t ha,(-1) respectively). The oils isolated by steam distillation from the flowers and leaves, were analyzed by GC and GUMS. The flowers and the leaves of each species showed very similar qualitative oil compositions and the leaves, on average, were richer in oil contents. The oil yields between the flowers and leaves showed differences highly significant (on average 1.8 and 150.3 kg ha,(-1) respectively). Tagetes erecta, T. minuta, T. patula and T. tenuifolia comprised the same pool of components (dihydrotagetone, tagetones, ocimenones and piperitone) which showed different and typical ratios in each species and, piperitone, (E)-tagetone, terpinolene and (E)-ocimenone were those more abundant respectively. Tagetes filifolia and T lucida had methyl chavicol as the main compound.