Synergistic Effects of Pressure, Temperature, CO2 Flow Rate and Co-Solvent on Bioactive Contents of Thai Fingerroot (Boesenbergia rotunda (L.) Mansf.) Extracts.

This study investigated the use of supercritical carbon dioxide (CO2) to extract bioactive compounds from Thai fingerroot (Boesenbergia rotunda), focusing on the effects of pressure, temperature, CO2 flow rate, and ethanol co-solvent concentration. A central composite design within a response surface methodology framework was employed to optimize the total extraction yield, total phenolic content (TPC), and total flavonoid content (TFC). Conventional ethanol maceration was used as a benchmark. High-performance liquid chromatography identified the major compounds in the extracts, such as pinostrobin and pinocembrin. The results showed that the yield, TPC, and TFC increased with higher pressure, CO2 flow rate, and co-solvent levels, whereas higher temperatures had a negative effect (p ≤ 0.05). Interactions between pressure and temperature favored the yield and TPC but not TFC. The optimal conditions-250 bar, 45 °C, 3 L/min CO2 flow rate, and 100% ethanol-produced a yield of 28.67%, TPC of 354.578 mg GAE/g, and TFC of 273.479 mg QE/g. These values exceeded those obtained using conventional extraction (9.91% yield, 332.86 mg GAE/g TPC, and 77.57 mg QE/g TFC at 60 min). The regression models showed strong predictive accuracy (R2 > 0.9). Pinostrobin and pinocembrin were the dominant phenolic compounds. These findings demonstrate the superior efficiency of supercritical CO2 extraction for isolating phenolic compounds from B. rotunda.