Preparation method and use of low-polarity chenopodium quinoa saponin monomer

A method of preparing a low-polarity Chenopodium quinoa saponin monomer, the method comprising:

• S1
• weighing Chenopodium quinoa bran;
• subjecting the Chenopodium quinoa bran to heating treatment with superheated steam at a temperature of 110° C. to 120° C. for 1 hour to 2 hours;
• air-drying a resulting heat-treated bran to have a water content of not greater than 10%;
• crushing a resulting air-dried Chenopodium quinoa bran and sieving a resulting crushed Chenopodium quinoa bran by passing through a 40-mesh sieve;
• subjecting a resulting sieved Chenopodium quinoa bran to extraction with 70% ethanol at 60° C. for 0.5 h;
• subjecting an obtained extract to a first concentration in a vacuum decompression concentration tank until a concentrate has no alcohol taste;
• subjecting the concentrate obtained from the first concentration to saponin purification by using HP-20 macroporous resin with a volume 15 times to 30 times that of the concentrate to obtain an eluate;
• subjecting the eluate to a second concentration again in the vacuum decompression concentration tank and recovering ethanol, then spray-drying a concentrated solution obtained from the second concentration at a temperature of 100° C. to 120° C. to obtain a Chenopodium quinoa saponin mixture;
• and
• S2
• subjecting the Chenopodium quinoa saponin mixture obtained in S1 to gradient elution with a 20% aqueous methanol solution, a 40% aqueous methanol solution, and an 80% aqueous methanol solution sequentially through a reverse-phase chromatographic column;
• collecting an eluate after elution with the 80% aqueous methanol solution;
• and
• concentrating and drying the eluate by using a rotary evaporator and recovering methanol, obtaining the low-polarity Chenopodium quinoa saponin monomer, namely a phytolaccagenic acid with a purity of not less than 90%.