Developing a Sufficient Protocol for the Enhancement of α-Glucosidase Inhibitory Activity by Urena lobata L. Aeroponic Hairy Roots Using Exogenous Factors, a Precursor, and an Elicitor

Aeroponics is considered as a potential method for the culture of herbal plants due to the high growth rate, quantity and quality enhancement of secondary metabolites, and substantial environmental progress associated with this method. The aim of this study was to develop a sufficient protocol for successful Urena lobata hairy root induction by Agrobacterium rhizogenes ATCC 15834, using a precursor and elicitor to enhance α-glucosidase inhibitory activity (GIA) of aeroponic hairy roots (AHRs) in greenhouse conditions. In this study, we found that the optimized procedure (10 min, Woody plant medium (WPM), 1/25 salt strength) had an outstanding effect with a reduction in the rooting time (RT), promotion of the rooting rate (RR), and increase in the fresh weight (FW) and dry weight (DW) compared with the original procedure (30 min, Murashige and Skoog (MS) medium, 1/25 salt strength) after 30 days of culture. The highest DW, GIA, flavonoid (FLA) and phenolic (PHEL) contents were observed for individual addition of 10 mM phenylalanine (PA) or 50 mM chitosan (CS) in the late exponential phase (eighth week) with 15 days of elicitation compared to the control AHRs. However, individual treatment was less effective than the combination of the two. Positive correlations among the GIA, FLA and PHEL indicate that AHRs accumulated phenolic compounds, leading to an increase in the GIA by a synergistic effect. In conclusion, the culture of Urena lobata AHRs with PA and CS is an efficient procedure to produce GIA material in greenhouse conditions.