Phytochemical characterization and biological activities of essential oil from Anethum graveolens L.: grown under water deficit stress and boron spraying

Background Anethum graveolens L. (dill) is an economically important aromatic plant cultivated for its seeds and essential oil. Dill straw is commonly treated as an agricultural by-product, despite its potential as an alternative source of essential oil. Water deficit stress and the boron (B) foliar application, represent key factors influencing the plant growth, yield, and essential oil composition. This study aimed to evaluate the effect of the boron application at different rates on the growth, seed yield, straw yield, and the essential oil content and composition of dill under varying irrigation regimes, and to assess the biological activities of the obtained essential oils. Materials and methods Field experiments were carried out to study the effect of boron (B) fertilization (0, 150 and 300 ppm) on the seed yield, and volatile oil of dill under water deficit stress conditions. The oil was obtained by hydro-distillation extraction method using Clevenger apparatus. Chemical analysis of the oil was done by using gas chromatography and mass spectrometry (GC-MS). The biological activities of the seed essential oil were evaluated. Results Irrigation at 100% of crop evapotranspiration (ET) combined with 300 ppm B produced the highest seed yield, straw yield, and straw oil yield, while 100- % ET combined with 150 ppm B resulted in the highest seed oil yield. High water use efficiency (WUE) for seed yield and seed oil yield was achieved at 50% ET with 150 ppm B, whereas, the maximum WUE for straw yield and straw oil yield was recorded at 50- % ET with 300 ppm B. GC-MS analysis identified carvone and limonene as the major compounds in dill seed oil, while α-phellandrene and limonene predominated in straw oil. The maximum carvone content in seed oil and α-phellandrene content in straw oil were obtained at 100% ET with 150 ppm B. The Maximum limonene content in both seed and straw oils was recorded under 75- % ET combined with 150 ppm B. The essential oil demonstrated significant antimicrobial, antibiofilm, antioxidant, and insecticidal activities. Conclusions The Boron foliar application combined with optimized irrigation regimes significantly influenced the yield, water use efficiency, and essential oil composition of A. graveolens . Dill straw represents a valuable and hitherto underutilized source of essential oil with a distinct chemical profile compared to seed oil. The biological activities of both oils support their potential application in food preservation and plant protection. These findings provide a basis for sustainable utilization of dill crop residues and optimization of cultivation practices under water-limited conditions.