Extending the applicability of pressurized hot water extraction to compounds exhibiting limited water solubility by pH control: curcumin from the turmeric rhizome |
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Authors: | Euterpio Maria Anna Cavaliere Chiara Capriotti Anna Laura Crescenzi Carlo |
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Institution: | (1) Department of Pharmaceutical and Biomedical Science, Salerno University, Via ponte don Melillo, 84084 Fisciano, SA, Italy;(2) Department of Chemistry, University of Rome “La Sapienza”, Piazzale Aldo Moro 5, 00185 Rome, Italy; |
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Abstract: | Pressurized hot water extraction (PHWE, also known as subcritical water extraction) is commonly considered to be an environmentally
friendly extraction technique that could potentially replace traditional methods that use organic solvents. Unfortunately,
the applicability of this technique is often limited by the very low water solubility of the target compounds, even at high
temperatures. In this paper, the scope for broadening the applicability of PHWE by adjusting the pH of the water used in the
extraction is demonstrated in the extraction of curcumin (which exhibits very limited water solubility) from untreated turmeric
(Curcuma longa L.) rhizomes. Although poor extraction yields were obtained, even at high temperatures when using degassed water or neutral
phosphate buffer as the extraction medium, yields exceeding those obtained by Soxhlet extraction were achieved using highly
acidic pH buffers due to curcumin protonation. The influence of the temperature, pH, and buffer concentration on the extraction
yield were investigated in detail by means of a series of designed experiments. Optimized conditions for the extraction of
curcumin from turmeric by PHWE were estimated at 197 °C using 62 g/L buffer concentration at pH 1.6. The relationships between
these variables were subjected to statistical analysis using response surface methodology. |
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