Determination of Oleanolic and Ursolic Acids in Hedyotis diffusa Using Hyphenated Ultrasound-Assisted Supercritical Carbon Dioxide Extraction and Chromatography
Table 2
Comparison of extraction yields and extraction conditions obtained by the HRE, SC–CO2 and HSC–CO2 methods.
Extraction parameters
Extraction mode
HRE
SC–CO2
HSC–CO2
Herbal sample
HD3
HD3
HD3
Mean particle size (mm)
0.355
0.355
0.355
Plant weight (g)
5
5
10
Stirring rate (rpm)
300
—
—
Static extraction time (min)
—
25
15
Ultrasonic frequency (kHz)
—
—
40
Duty cycle (%)
—
—
79
Dynamic time (min)
—
140
110
Extraction time (min)
60 × 4 (4 cycles)
165
125
Extraction temperature (°C)
75 (Boiling point)
56
56
Extraction pressure (MPa)
—
28.2
28.2
Liquid/solid ratio (mL/g)
16
64.4
50.6
CO2 flow rate (mL/min)
—
2.3
2.3
Extraction cycles
4
—
—
Cosolvent (v/v%)
—
82% ethanol
82% ethanol
Percentage of cosolvent (82% ethanol) in SC–CO2
—
12.5%
12.5%
OA:
Yield (mg/g)a
0.762 ± 0.030
0.824 ± 0.032
0.917 ± 0.033
Ethanol (v/v%)b
70%
—
—
RSD (%)c
3.94
3.88
3.696
UA:
Yield (mg/g)a
2.964 ± 0.094
3.175 ± 0.114
3.540 ± 0.135
Ethanol (v/v%)b
90%
—
—
RSD (%)c
3.17
3.59
3.825
Values are written as the mean ± SD of six replications and are calculated based on plant dry weight basis. bEthanol concentration in water (v/v%). cRSD (%) = (SD/mean) × 100.
