| Summary: | 碩士 === 國立中興大學 === 化學工程學系 === 94 === This study investigated hot pressurized ethyl acetate (EA), ultra-sonic EA, and supercritical carbon dioxide (SC-CO2) added with EA extractions to recover 3,5-Diprenyl-4-Hydroxycinnamic Acid (DHCA) from Brazilian propolis. Response Surface Methodology (RSM) was applied to find operation conditions in obtaining the highest recovery and purity of DHCA for these extractions. The maximum content of DHCA in propolis is 91.9 (mg/g), obtained by 16-hour Soxhlet extraction of one gram solid with 120mL EA.
Center composite RSM schemes designed at 95 ◦C, 2.5-hour and 55 ◦C, 2.5-hour were individually employed for hot pressurized and ultra-sonic extractions. For hot pressurized extraction, predicted maximum recovery and purity of DHCA are 88.79 wt% and 16.26 wt%, which is corresponding to experimental data at the design point. However, for ultra-sonic extraction, the DHCA recovery is only up to 75.03 wt% and is still increasing with temperature in the range investigated, but the DHCA purity also attains 16.26 wt% close to that of the design point. Our experimental results further indicated that temperature and addition ratio of EA are two major factors to influence the recovery and purity of DHCA for SC-CO2 extraction. The 50 ◦C and 4 wt% EA addition was selected as the RSM design point. Then, the DHCA recovery substantially increased from 3.68% (no adding) to 13.88wt% (6 wt% EA adding) and was still increasing, while the maximum DHCA purity reached 43.38 wt% at 50 ◦C and 2 wt% EA addition, slowly decreased in the ranges investigated. Nevertheless, the DHCA purities in the SC-CO2 extracts are all over 40wt%.
Normal phase Sil-60 resin column purification coupled with liquid-liquid n-hexane and methanol extractions of these three extracts produced 95 wt% purity of DHCA. The largest total DHCA recovery in this column purification was 4.05 wt% only for the purified extract of hot pressurized EA treated with L-L extractions. Without pre-treated L-L extractions, only the purified SC-CO2 extract attained the 95 wt% purity and obtained 9.41wt% of the largest total DHCA recovery. Finally, anti-oxidative abilities of scavenging DPPH free radical and the inhibition of low density lipid (LDL), treated by the 95wt% purity DHCA and those extracts, revealed a positive correlation between the quantity of DHCA and anti-oxidative ability.
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