Results and discussion
The crude extract of Dendrobium candidum extracted by SFE is mixed and analyzed according to the analysis method in 2.4.
It can be found that the SFE crude extract has various components. According to related calculations, SFE technology can obtain crude extract 46 g / kg and naringenin 30 mg / kg from Dendrobium candidum. It can be found that most of the soluble substances can be extracted 2 hr before extraction.
After 2 hr, the extraction rate gradually decreases, but there are still substances with lower solubility that are continuously extracted.
The cumulative yield of naringenin shows that the extraction trend of naringenin and the total product of Dendrobium officinale is basically the same, and the extraction rate rises sharply within 2 hr before extraction, indicating that naringenin can be extracted together with soluble substances. After 9 hr, the extraction rate gradually leveled off, indicating that most of the naringenin had been basically extracted.
Co-solvent proportion screening results
At 20 MPa, 40 ℃ and CO2 flow rate of 3.625 g / min, the proportion of ethanol is 12 wt%,
In addition, the standard naringenin and the crude extract of Dendrobium officinale are mixed in a ratio of 2: 1, and then analyzed by SFC.
It can be seen that when ethanol is 12 wt%, most of the substances in Dendrobium extract can not be washed out due to insufficient solvent power of the mobile phase.
When the percentage of ethanol is increased to 15 wt%, although there is a better Separation effect, but its residence time is longer; if the proportion of co-solvent is increased to 20 wt%, it will lead to poor relative selectivity.
Only when ethanol is 18 wt%, not only is the selectivity good, but the residence time is more appropriate, and the mobile phase has better dissolving power. It was found that naringenin appeared at about 8.8 minutes, while strongly adsorbed substances appeared at about 11.9 minutes.
Based on the above results, the final proportion of the auxiliary solvent ethanol was 18 wt%.