Optimizing the Precipitation of Bioactive Compounds From Extracted Curcuma longa Linn. Using Gas Anti-Solvent Process

Turmeric is a medicinal herb that can be used in a wide range of applications, such as food ingredients, cosmetics, and traditional medicine. The active ingredients found in turmeric are curcumin (CUR), desmethoxycurcumin (DMC), and bisdesmethoxycurcumin (BMDC). The aim of this research was to precipitate the active ingredients from a turmeric extract using the gas anti-solvent process with carbon dioxide as the anti-solvent. The effects of solvent type (ethanol, methanol, and acetonitrile), precipitation temperature (25°C–45°C), and CO₂ flow rate (4–12 mL/min) on the amount of precipitates were investigated using the Box–Behnken design of experiments. The precipitates were analyzed for curcuminoids and CUR content using HPLC and were tested for antioxidant activity. It was found that solvent type and temperature were significant variables at a 5% significance level on the amount of precipitates. Using a mixture of ethanol and methanol (77.5% v/v ethanol) with a polarity index of 4.48 as the solvent, a precipitation temperature of 25.40°C, and a CO₂ flow rate of 7.56 mL/min was found to be the optimal conditions for achieving the highest amount of precipitates. At the optimal conditions, the amounts of curcuminoids and CUR precipitates were found to be 27.33 ± 0.23 and 13.30 ± 0.12 mg/5 mL of extracted solution, respectively. In the antioxidant studies, the Trolox equivalents found in the products at the optimal conditions using DPPH and ABTS assays were 38.19 ± 0.17 and 65.96 ± 2.36 mg/5 mL of extracted solution, respectively. The total phenolic content was found to be 30.84 ± 1.80 mg/5 mL of extracted solution.