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Phosphorus belongs to the crucial bioelements that cause eutrophication, and phosphates, easily assimilated by organisms, are widespread in the environment. Phosphates can be of natural or anthropogenic origin and can derive from various point or non-point sources. Knowledge about the origin of nutrients is necessary to effectively manage, protect, and revitalize water resources. To recognize various phosphate sources in the study area of our research, i.e., the Vistula and Bug interfluve (SE Poland), we used the oxygen isotopic signature of phosphate ions (δ18O-PO4), which has been successfully used in recent decades as a tracer of phosphorus cycling in water studies. We measured the δ18O-PO4 of dissolved inorganic phosphates (DIPs) extracted from various phosphate sources. The obtained results are as follows: For springs, the δ18O-PO4 value varied from +14.8‰ to +18.5‰; for riverine samples, from +10.3‰ to +18.6‰, which were significantly location-dependent; while waste water treatment plant effluents ranged from +12.4‰ to +15.6‰. Two tested drainage water samples had similar isotopic compositions (+16.7‰ and +17.3‰). In the case of two analyzed bedrock samples, the δ18O-PO4 values, which were similar (+20.5‰ and +21.7‰), are close to the existing data on sedimentary bedrocks derived from similar geological periods. The obtained results can be helpful in future research aimed at identifying phosphate sources and P cycling in the studied area. [ABSTRACT FROM AUTHOR]

Arnica montana L. is one of Europe's endemic endangered medicinal plants, with diverse biological activities commonly used in medicine, pharmacy, and cosmetics. Its flower heads are a rich source of raw material, with antibacterial, antifungal, antiseptic, anti-inflammatory, antiradical, antioxidant, and antitumor properties. The objective of the present study was (i) to characterize the chemical composition of flower heads of A. montana plants cultivated under nitrogen fertilization, (ii) to identify the impact of the nitrogen fertilization and extraction method (water, ethanol) on the antioxidant activity of extracts, and (iii) to determine the role of different nitrogen doses applied during plant cultivation and different extraction methods in the anticancer activity of the extracts through analysis of apoptosis and autophagy induction in HT29, HeLa, and SW620 cell lines. The present study shows that nitrogen is a crucial determinant of the chemical composition of arnica flower heads and the antioxidant and anticancer activity of the analyzed extracts. Nitrogen fertilization can modify the composition of pharmacologically active substances (sesquiterpene lactones, flavonoids, essential oil) in Arnicae flos. The content of sesquiterpene lactones, flavonoids, and essential oil increased with the increase in the nitrogen doses to 60 kg N ha−1 by 0.66%, 1.45%, and 0.27%, respectively. A further increase in the nitrogen dose resulted in a decrease in the content of the analyzed secondary metabolites. Varied levels of nitrogen application can be regarded as a relevant way to modify the chemical composition of arnica flower heads and to increase the anticancer activity, which was confirmed by the increase in the level of apoptosis with the increase in fertilization to a level of 60 kg N ha−1. The fertilization of arnica plants with low doses of nitrogen (30 and 60 kg N ha−1) significantly increased the LOX inhibition ability of the ethanol extracts. The present study is the first report on the anticancer activity of A. montana water extracts, with emphasis on the role of water as a solvent. In further studies of factors modifying the quality of Arnicae flos, attention should be paid to the simultaneous use of nitrogen and other microelements to achieve synergistic results and to the possibility of a more frequent use of water as a solvent in studies on the biological activity of A. montana extracts. [ABSTRACT FROM AUTHOR]