Green and efficient extraction of total glucosides from Paeonia lactiflora Pall. ‘Zhongjiang’ by subcritical water extraction combined with macroporous resin enrichment

In this work, a green and efficient method of subcritical water extraction (SWE) combined with macroporous resin purification (MRP) of the total glucosides (TGP) from Paeonia lactiflora Pall. ‘Zhongjiang’ was established. The hydrolysis of albiflorin and paeoniflorin in subcritical water was initially studied. Albiflorin and paeoniflorin were stable in subcritical water at 180 °C for 10–30 min but unstable at high temperatures (T ≥ 220 °C) for a long time (time ≥ 40 min). Then, the response surface methodology (SMR) was used to optimise the SWE process for an enhanced extraction yield of TGP. The best extraction conditions obtained were as follows: extraction time 22 min, extraction temperature 158 °C, and liquid-to-solid ratio 21 mL/g. Under the optimal conditions, the maximum extraction yield of TGP reached 7.08%. In addition, the efficient AB-8 macroporous resin purification method of TGP was established from the SWE crude extract. The optimised loading amount was 1.6 BV (bed volume) of the TGP crude extract, and the desorption conditions were as follows: eluting 3 BV with ultrapure water, and then eluting with 20% ethanol at 2 BV·h−1 to collect 12 BV eluate. After the AB-8 resin treatment, the TGP content increased from 32.5% in the crude extract to 89.6% (albiflorin ≥ 25%, paeoniflorin ≥ 63%), and the recovery rate of TGP reached 84.2%. These results indicate that SWE combined with MRP is a simple, green, and effective technology for the TGP extraction from P. lactiflora ‘Zhongjiang’.