Pressurized liquid extraction (PLE)
This green method was first proposed by Richter et a (1996) [80] and is considered as an environment-friendly method. The technology is now known by various names: Pressurized liquid extraction (PLE), Accelerated solvent extraction (ASE), Enhanced solvent extraction, Subcritical water extraction (SWE) and Solvent extraction at high pressure [81, 82]. The use high pressure (500–3000 psi) and high temperature (50–200 °C) maintain the solvent condition before its normal boiling point which results in reduce the extraction time and the solvent consumption, increases extraction yield and facilitates the process This method is not suitable for compounds sensitive to heat due to high temperature [22, 82, 83]. Water is considered as one of the solvents used in this method that if maintained in a liquid state by pressure, can shows a variety of behaviors such as methanol or ethanol. In general, this technology is not considered as a valuable method on an industrial scale due to the technological challenges [82, 84, 85].