Effects of nutrient solution temperature on the concentration of major bioactive compounds in red perilla

Red perilla Perilla frutescens is used as food, stomachic and antitussive crude drugs, and anti-allergy supplements. The major bioactive compounds of red perilla are perillaldehyde PA, rosmarinic acid (RA), luteolin (LU), and anthocyanin (ANT). In this study, we investigated the effects of 6 days low 10, 12, and 15 degrees C and control (20 degrees C) nutrient solution temperature (NST) treatments on plant growth and major bioactive compound concentrations in red perilla leaves at the node position. No significant difference was detected in the dry weight of leaves of the main shoot, which is the main part harvested, among the treatments. However, leaf water content (%) tended to decrease with a decrease in NST, especially in plants grown at 10 degrees C NST, which exhibited values significantly lower than those of plants grown at 15 degrees C and 20 degrees C NSTs. PA and ANT concentrations in the 3rd to 5th nodes did not differ among treatments. Conversely, RA concentration increased with a decrease in NST, irrespective of the node position. LU concentration at 10 degrees C NST was the highest in all treatments, irrespective of the node position. This suggested that the production of bioactive compounds under the low NSTs differed depending on leaf maturity stage and compound. Additionally, the contents of RA and LU in the whole plant increased because there was no reduction in growth of the harvested part under the low NSTs. Therefore, 6 days exposure to root-zone temperatures at 10 degrees C appears to be an effective method to increase both RA and LU concentrations and their contents in the whole plant of red perilla for its use as a crude drug or medicinal material.