LAUSR

The callus cultures of Fagonia indica could prove as factories for the production of important phytochemicals when triggered through different types of stress. In this study, we initiated callus cultures from healthy stem explants in the presence of iron-doped zinc oxide nanoparticles (Fe-ZnO-NPs). We performed experiments with the callus cultures of F. indica to determine the impact of Fe-ZnO-NPs in concentrations (15.62–250 µg/mL) on biomass accumulation, production of important phenolic and flavonoids, and antioxidative potential. Our results showed that maximum callus biomass [Fresh weight (FW) = 13.6 g and Dry weight (DW) = 0.58 ± 0.01] was produced on day 40 when the media was supplemented with 250 μg/mL Fe-ZnO-NPs. Similarly, maximum total phenolic content (268.36 μg GAE/g of DW) was observed in 40 days old callus added with 125 μg/mL Fe-ZnO-NPs. Maximum total flavonoid content (78.56 μg QE/g of DW) was recorded in 20 days old callus grown in 62.5 μg/mL Fe-ZnO-NPs containing media. Maximum total antioxidant capacity (390.74 µg AAE/g of DW) was recorded in 40 days old callus with 125 μg/mL Fe-ZnO-NPs treated cultures, respectively. Similarly, the highest free radical scavenging activity (93.02%) was observed in callus derived from media having 15.62 µg/mL Fe-ZnO-NPs. The antioxidant potential was observed to have positive correlation with TPC (r = 0.44). HPLC analysis showed that Fe-ZnO-NPs produced compounds (e.g., Epigallocatechin gallate) that were either absent or in lesser quantities in the control group. These results showed that Fe-ZnO-NPs elicitors could increase the biomass and activate secondary metabolism in F. indica cells. Supplementary Information The online version contains supplementary material available at 10.1007/s11240-021-02123-1.