“…It is dificult to compare the published results, having in mind the fact that authors analyzed the plant material from various regions, characterized by their specific enviromental and ecological factors, and in many cases phenological phase of the analyzed plant material was not given. Some authors stated different chemical compositions of H. perforatum essential oils depending on the plant organs examined (leaves, flowers, stems) [28,41]. Moreover, the differences in the composition of essential oils may originate from different varieties within the same species [27], and as in most papers this taxonomic category was not given, the comparison of essential oils becomes more difficult.…”