3.7. Analysis of Triterpenoid Saponins

Cells were collected and dried to a constant weight at 55 °C, and then thoroughly ground into powder. A small amount of each sample (0.50 g) was transferred into a centrifuge tube containing 20.0 mL methanol, followed by ultrasonic treatment for 2 h. An HPD-100 macroporous resin column was used for loading the methanol extracts. The extracts of different transgenic cells and non-transgenic cells were dried in an oven at 50 °C and diluted with 70% methanol to 25.0 mL. The absorbance was measured according to the methods of the A₅₅₀ and the standard curve and PNS in each sample was calculated. The systems and samples used in it are as described in our previous study [24]. Monomer saponin content was determined by the high-performance liquid chromatography (HPLC) on an ULTIMATE 3000 LPG-3400A system (Dionex, Sunnyvale, CA, USA) using the 25.0 mL extracts. A Waters Symmetry C18 column (5 µm, 4.6 × 250 mm) was used for the HPLC analysis with water and acetonitrile as the mobile phase. The retention time and peak areas were performed to identify and quantify the ginsenosides calculated with standard ginsenosides purchased from the National Institutes for Food and Drug Control (Beijing, China).