Comparison of resveratrol, SOD activity, phenolic compounds and free amino acids in Rehmannia glutinosa under temperature and water stress

The objective of this study was to determine the contents of secondary metabolic substances such as resveratrol, SOD, phenolic compounds and free amino acids in Rehmannia glutinosa under environmental stress. The content of resveratrol varied from 2.96 to 38.87 μg g−1, while SOD activity varied from 9.40 to 28.43%. Of the 16 individual phenolic compounds, myricetin showed the highest concentrations (34.30, 60.96, 35.70 μg g−1) in the water deficiency (−1.18 MPa) and control (−1.04 MPa) and low temperature (15 °C) treatment. The 21 free amino acids in R. glutinosa were only detected in small amounts and varied from 0.82 to 5.69 μg g−1. Overall, these substances decreased at high temperature and with a water deficiency. Other than for SOD activity, these substances were negatively correlated (r2 = −0.99**) with temperature and positively correlated with water stress (r2 = 0.99***). Also, other than for SOD activity under the water deficiency treatment, resveratrol, SOD activity, phenolic compounds and free amino acids had over correlation coefficients (r2 = 0.99**) in all treatments. Our study suggests that it might be feasible to improve or develop R. glutinosa cultivation methods with high functional substances such as resveratrol, even under poor environmental conditions for cultivation.