Different indole-3-acetic acid and 6 benzyl amino purine concentrations affect biomass, phenolic profile, and bioactivity in Mentha rotundifolia L.

Although the use of phytohormones for crop improvement has great potential, little is known about the molecular effects of phytohormones in crops. This work investigated the effect of the exogenous application of plant growth regulators (PGRs), indole-3-acetic acid (IAA), and cytokinin-like 6-benzyl amino purine (BAP) on plant biomass and the phytochemical and biological parameters of Mentha rotundifolia L. aerial parts and roots. The results showed that the application of IAA and BAP significantly influenced the accumulation of phenolic compounds in the plant organs. Treatment with PGRs also induced remarkable increases in the amounts of individual phenolic compounds, with the greatest increases observed for salvianolic and rosmarinic acids in the aerial parts treated with 20 or 10 mg/mL of BAP. Salvianolic acid also showed the most significant increase in the roots of plants treated at 10 mg/mL (from 18.232 to 41.317 µg/g of extract). Furthermore, enhanced antioxidant and inhibitory enzyme effects in the treated plants was observed. Our findings suggest that exogenous hormones could be used to improve the synthesis of phenolic compounds and, as a result, the bioactivity of medicinal or food plants.