On the other hand, as the interactions among single components of essential oils are still an open matter [38], a tentative hypothesis could be that the synergic and antagonistic effects of oil compounds were the cause of different activities of the two oils; the synergistic activity of monoterpens, such as terpinolene and pinenes, and sesquiterpens, such as β-caryophyllene, in plant essential oils has been in fact demonstrated in previous studies [39] and [40].