Chemical components of essential oils and biological activities of the aqueous extract of Anethum graveolens L. grown under inorganic and organic conditions

BACKGROUND: In sustainable agriculture, the use of farmyard manure (FYM) is of great interest to environmental security and is effective as a good nitrogen source for sustainable crop production. Therefore, determining the effective doses of FYM that will be an alternative to chemical fertilizers, is also important to improve soil fertility and produce healthy products. This study aimed to determine the effects of FYM and ammonium nitrate (AN) fertilizers on the biological value and essential oil content of dill (Anethum graveolens L.). METHODS: Different doses FYM (7.5, 10, 12.5 and 15 t ha⁻¹) and AN (30, 60, 90 and 120 kg ha⁻¹) were applied by sowing and compared to a control group (no manure). We evaluated the chemical constituents as well as the biological activities of dill herbs and seeds growing at various doses of FYM and AN fertilizers. RESULTS: The most abundant components of essential oils were found to be dill apiole (11.96 ± 0.83 and 18.65 ± 1.89%) and carvotanacetone (15.90 ± 2.34 and 21.76 ± 1.62%) in the leaves and seeds, respectively. Limonene (9.01 ± 1.11%), 4-isopropyltoluen (8.24 ± 0.89%), dill ether (9.13 ± 1.12%) and mycrene (7.44 ± 0.68%) were major essential oils components in herbs. The highest concentration of the essential oil components was determined as 12.5–15 t ha⁻¹ in FYM and 90 AN applications. From the effective concentration (EC₅₀) of the samples, it was seen that 60 kg ha⁻¹ AN infusion, 120 kg ha⁻¹ AN decoction as well as 7.5 t ha⁻¹ FYM and 10 t ha⁻¹ FYM essential oils had the highest DPPH, ABTS⁺ and superoxide anion radical scavenging activity as shown by the lowest value of EC₅₀ compared to the control. Although the antioxidant activities of the samples were significantly lower than those of the reference antioxidant gallic acid, it was evident that they did show the antioxidative potential for hydrogen and a single electron donor activities, thus could serve as free radical scavengers, and act as reductant. In particular, the highest total phenolic content (18.36 ± 0.35 mg g⁻¹) was found in the infusion extract after applying the 60 kg ha⁻¹ AN fertilizer. Essential oils extracted from the seeds also exhibited strong antibacterial activity against Staphylococcus epidermidis, Enterococcus faecalis, and Pseudomonas aeruginosa. The highest antibacterial activity against all tested microbial species was observed with the 10 t ha⁻¹ FYM application. CONCLUSION: The findings of the study suggest that the application of FYM has promising effects on dill leaf, seed, and herb and can be considered as a suitable substitute for chemical fertilizers when growing dill, a plant with increasing importance and demand.