LAUSR

Abstract Dracocephalum kotschyi Boiss. is one of the important threatened traditional species of medicinal herbs; last pharmaceutical research has shown that rosmarinic acid (RA) and methoxylated flavonoids, particularly, xanthomicrol and cirsimaritin of this plant have anti-cancer, anti-spasm and anti-platelet properties. In this study, Hairy roots were derived from four-week-old leaves inoculated with Agrobacterium rhizogenes strain ATCC15834. The influence of various silicon dioxide nanoparticles (SiO2 NPs) concentrations at two exposure time (24 and 48 h) on growth, antioxidant enzyme capacity, total phenols and flavonoids content (TPC and TFC) and some biochemical traits were investigated. The expression of phenylalanine ammonia-lyase (pal) and rosmarinic acid synthase (ras) genes expression in RA biosynthetic pathway were quantified. The biomass of cultures has substantially by elicitation raised in comparison with control. The activity of antioxidant enzymes, TPC and TFC were impressed by the concentration and duration of treatment. The high RA content (1016.6 μg/g FW) with 8.26-fold increase compared to control, was observed in hairy roots culture elicited with SiO2 NPs (100 mg/L) after 48 h exposure time. The pal and ras genes expression rate in this elicitor concentration and exposure time enhanced notably. Anticancer flavonoids including xanthomicrol, cirsimaritin and isokaempferide showed 13, 13.42 and 10-fold increases compared to the control respectively. Stimulation of D. kotschyi hairy roots by SiO2 NPs caused huge increase in induction and production of important pharmaceutical compounds such as rosmarinic acid and xantomicrol.