SA quantification was performed using RP-HPLC (Agilent 1200, Agilent technology, USA) equipped with Thermo-C18 column (250 mm × 4.6 mm, 5 µm) and fluorescence detector under 294 nm of excitation wavelength and 426 nm of emission wavelength. The injection volume was 10 µL, and flow rate was 0.5 mL min−1 at 25 °C. The mobile phase was sodium acetate buffer (0.2 M):methanol (9:1 v/v).
The SA extraction method was modified according to that of Yuan et al.16 (link). Leaf samples (1 g) were ground in liquid nitrogen and extracted ultrasonically in 1 mL of methanol. After centrifugation at 10,000 g for 15 min, the residue was re-extracted two times as above. The supernatants were combined and freeze dried. The concentrate was dissolved in 0.5 mL of trichloroacetic acid. After oscillation for 2 min, the mixture was extracted twice with 0.8 mL of acetic acid ester:cyclohexane (1:1 v/v). Organic phases were combined and freeze dried. The concentrate was dissolved with 0.6 mL of HPLC mobile phase and filtered with 0.22 µm Millipore membrane for detection.
The SA extraction method was modified according to that of Yuan et al.16 (link). Leaf samples (1 g) were ground in liquid nitrogen and extracted ultrasonically in 1 mL of methanol. After centrifugation at 10,000 g for 15 min, the residue was re-extracted two times as above. The supernatants were combined and freeze dried. The concentrate was dissolved in 0.5 mL of trichloroacetic acid. After oscillation for 2 min, the mixture was extracted twice with 0.8 mL of acetic acid ester:cyclohexane (1:1 v/v). Organic phases were combined and freeze dried. The concentrate was dissolved with 0.6 mL of HPLC mobile phase and filtered with 0.22 µm Millipore membrane for detection.
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