Browsing by Person "Salomon, Lysanne"

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Investigations into the secondary metabolite profile and bioactivity characteristics of various Achillea species grown under different environmental conditions
(2022) Salomon, Lysanne; Kammerer, Dietmar R.
Various Achillea species, including common yarrow Achillea millefolium L., are known to be rich in bioactive substances and are important medicinal plants in modern phytotherapy. In contrast, the alpine species Achillea atrata L. has hardly been studied so far regarding its bioactive compounds and the concomitant potential for human health. Having this in mind, the present work combined studies on the cultivation of A. atrata in different habitats with the phytochemical characterization of its secondary metabolite profile aiming at the generation of plant material with a defined and consistent phenolic profile suitable for pharmaceutical application. Particular emphasis was put on potential relationships between phytochemical profile and bioactivity, and these parameters were considered in comparison with other Achillea species. The results presented in this thesis reveal that the cultivation of A. atrata can be realized at sites differing significantly in altitude and, consequently, in their climatic conditions. Environmental conditions were found to have only a minor impact on the secondary metabolite profile. Rather, differences of various chemotypes might be more decisive. However, the contents of individual phenolic components, especially phenolic acids, is strongly dependent on environmental factors and reach their maximum at increasing altitude levels. Significant differences in the occurrence of the identified phenolic compounds were found between flowers and leaves. In addition to the previously mentioned studies, A. millefolium, Achillea moschata Wulfen, and A. atrata were compared with respect to their phenolic profile and antibacterial activity against gram-positive bacterial strains (Staphylococcus, Propionibacterium). A. atrata showed more similarities in the secondary metabolite profile with the alpine A. moschata than with A. millefolium. The two alpine Achillea species only differed in the occurrence of four compounds. All three aforementioned Achillea species reduced the growth of the tested bacteria. A. atrata showed the highest activity against Propionibacterium acnes and Staphylococcus epidermidis, which are involved in the development of the skin disease Acne vulgaris. In addition, A. atrata exhibited pronounced anti-MRSA potential. Bioassay-guided fractionation of the corresponding extracts revealed that the high antimicrobial activity was due to the flavonoids apigenin, centaureidin, and nevadensin, which were detected exclusively in the most polar fraction and were present in high amounts in A. atrata. Additional studies on the bioactivity and phytochemistry of A. atrata proved that this species exhibits higher antioxidant activity compared to A. millefolium, which was significantly correlated with its total phenolic content. Further bioassay-guided fractionation confirmed the correlation between the mentioned flavonoids in the most polar fraction and the high antioxidant capacity of A. atrata. In conclusion, A. atrata may be an alternative source for the development of novel herbal drugs, based on its compound and bioactivity characteristics.