Enhanced production of pharmaceutically important metabolites using nanoelicitors treatment in callus cultures of <i>Tagetes erecta</i> L. variety sweet orange

<i>Tagetes erecta</i> L. (Asteraceae), commonly known as marigold, is an annual herb that possesses a variety of pharmaceutically important compounds. This study evaluates the effects of nanomaterials on the production of pharmaceutically important metabolites in <i>T. erecta</i> callus cultures. The results indicated that all three metabolites were simultaneously quantified using high-pressure thin layer chromatography. The highest quercetin yield (100.180 ± 0.48 mg g^-1 DW) (1.92-fold higher than the control) was obtained after treatment with 16 mg L^-1 zinc oxide nanoparticles. Caffeic acid was detected only in callus cultures treated with multi-walled carbon nanotubes (MWCNTs) and at certain concentrations of its bulk counterpart. The maximum yield of caffeic acid (35.567 ± 1.49 µg g^-1 DW) (35.56-fold higher than the control) was recorded at 4 mg L^-1 MWCNTs. Similarly, the highest yield of stigmasterol (112.197 ± 0.86 µg g^-1 DW) (5.60-fold increase than the control) was obtained at 16 mg L^-1 MWCNTs.