Ozonated water soaking improves the flower growth, antioxidant activity, and bioactive compound accumulation in Agastache rugosa

Abstract

Ozonated water (OW) is now being recognized as an innovative and eco-friendly solution for managing plant growth while also promoting the production of bioactive compounds and essential plant metabolites. This study aimed to identify the most effective duration of OW treatment to promote plant growth and accumulation of antioxidant activity and bioactive compounds in Agastache rugosa in a plant factory. Whole plants were subjected to OW soaking treatments for varying durations (0, 1, 10, 20, 40, and 80 s) at a concentration of 1 µmol·mol−1, once per week, at 0, 1, 2, 3, and 4 weeks after transplantation. Five weeks after transplantation, plant samples were collected for the analysis of their plant growth parameters, photosynthetic pigments and parameters, total flavonoid, antioxidant activity, and bioactive compounds. Stem length was decreased in all OW treatments, while the number of flower branches, the flower fresh and dry weights were significantly increased under 20, 40, and 80 s OW treatments than in the control group. The net photosynthetic rate decreased significantly in 20, 40, and 80 s OW treatments compared with the control. Chlorophyll a concentration was the highest in the 20-s OW treatment, and chlorophyll b concentration was the highest in the 10-s OW treatment. Total flavonoid levels in plants increased significantly under 20-, 40-, and 80-s OW treatments, and their antioxidant activity (superoxide dismutase, catalase, and peroxidase) were significantly higher under 40- and 80-s OW treatments than in the control. Rosmarinic acid content increased significantly under the 10- and 40-s OW treatments, whereas the tilianin and acacetin contents increased significantly under the 20-, 40-, and 80-s OW treatments compared to those in the control. Our results suggest that soaking whole plants in OW for 20–80 s enhances the flower growth and bioactive compounds in A. rugosa for medicinal use. Graphical Abstract

Optimization of salicylic acid concentrations for increasing antioxidant enzymes and bioactive compounds of Agastache rugosa in a plant factory

“…To extract the powdered shoot samples (20 mg DW), 2 mL of 90% MeOH was added, and the mixture was centrifuged at 1308 × g for 20 min. The concentrations of Chl a, Car, and Chl b were detected at wavelengths of 652.4 nm, 470 nm, and 665.2 nm, respectively, as per the protocol described by Lichtenthaler (1987) and Lam et al 2023 [ 20 , 21 ]. The DPPH activity was conducted at a wavelength of 517 nm, following the procedure described by More and Makola, 2020 [ 22 ].…”

“…To analyze the total flavonoid contents using colorimetric techniques, we followed the method outlined by Lin and Tang (2007) and Lam et al 2023 [ 21 , 23 ]; primarily, this method involved the use of aluminum chloride (AlCl 3 ). In summary, the process entailed mixing 20 mg of dry powder samples with 2 mL of 90% methanol, then subjecting them to sonication at 20°C for 20 minutes.…”

“…To determine the concentrations of RA, tilianin, acacetin, and the three acacetin glycosides, acacetin 7-O-(2"-O-acetyl)β-D-glucopyranoside (acacetin 1), acacetin 7-O-(6"-O-malonyl)β-D-glucopyranoside (acacetin 2), and acacetin 7-O-(2"-O-acetyl-6"-malonyl)β-D-glucopyranoside (acacetin 3), following the procedure described by Lam et al 2023 [ 21 ] 10 mL of 100% methanol was used to dissolve 200 mg of dry powder from flowers, leaves, roots, and stems. Before analysis, the mixture underwent 30 minutes of sonication.…”