Department of Pharmaceutical and Biomedical Science, Salerno University, Fisciano, SA, Italy.
Anal Bioanal Chem. 2011 Nov;401(9):2977-85. doi: 10.1007/s00216-011-5383-7. Epub 2011 Sep 21.
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.
加压热水提取（PHWE，也称为亚临界水提取）通常被认为是一种环保的提取技术，有可能替代使用有机溶剂的传统方法。不幸的是，即使在高温下，该技术的适用性也常常受到目标化合物极低的水溶性的限制。在本文中，通过调整提取过程中所用的水的 pH 值，拓宽 PHWE 适用性的范围，从未经处理的姜黄（Curcuma longa L.）根茎中提取姜黄素（其水溶性非常有限）。尽管即使在使用脱气水或中性磷酸盐缓冲液作为提取介质时，采用高温也只能得到很差的提取产率，但由于姜黄素质子化，使用高酸性 pH 缓冲液可以获得超过索氏提取产率的提取产率。通过一系列设计实验详细研究了温度、pH 值和缓冲液浓度对提取产率的影响。通过 PHWE 从姜黄中提取姜黄素的最佳条件估计为 197°C，缓冲液浓度为 62g/L，pH 值为 1.6。使用响应面法对这些变量之间的关系进行了统计分析。
