Improving essential oil production and antioxidant properties of Carum copticum L. by titanium dioxide nanoparticles and light spectrum interaction under hydroponic conditions.

Carum copticum L. is one of the medicinal plants belonging to the Apiaceae family that has significant pharmaceutical properties. This plant was first described by Carl von Linnaeus. Carum copticum possesses antimicrobial, antiseptic, antihypertensive, antihyperlipidemic, carminative, antiviral, anesthetic, antitussive, bronchodilatory, hepatoprotective and antiulcer effects which are practical nowadays. Considering the importance of C. copticum, we studied evaluation of titanium dioxide nanoparticles (TiO₂ NPs) and light spectrum such as white, white–blue and blue on improvement of antioxidant properties and essential oils. For this purpose, the seedlings were grown under controlled hydroponic conditions and after 3 weeks treated by spraying of different TiO₂ NPs concentrations (0, 100, 200, 300 and 400 ppm) on their leaves and then treated by the light. Afterwards, some of the physiological, phytochemical parameters and essential oils were analyzed. The results showed that 300 ppm TiO₂ NPs combined with white–blue light is significantly the most effective treatments for improving the quantity of physiological and phytochemical parameters in C. copticum. Furthermore, TiO₂ NPs and light play the role of elicitor that can induce remarkable enhanced changes in the desired parameters. In addition, studing of the essential oil contents of C. copticum using Gas chromatography–mass spectrometry demonstrated that thymol, α-pinene and γ-terpinene are the main essential oil components of this plant and the treated seedlings under 300 ppm TiO₂ NPs and white–blue light together showed a significant increase in the contents of thymol and γ-terpinene. Besides, α-pinene enhanced considerably at 400 ppm TiO₂ NPs combined with white–blue light spectrum.Key message: Titanium dioxide nanoparticles combined with the light spectrum may be considered as proper elicitors to enhance secondary metabolites and essential oils of C. copticum (L.). [ABSTRACT FROM AUTHOR]