Solvent extraction principle phenolic acids

Principle Instead of long-lasting extraction with different organic solvents, acids or bases in the Soxhlet apparatus is unsuitable for the extraction of most flavonoids, the Amberlite IR-45 (OH) ion-exchange resin was used for the extraction of plant phenolics. 

Tea leaves consist primarily of cellulose this is the principle structural material of all plant cells. Fortunately, the cellulose is insoluble in water, so that by using a hot water extraction, more soluble caffeine can be separated. Also dissolved in water are complex substances called tannins. These are colored phenolic compounds of high molecular weight (500 to 3000) that have acidic behavior. If a basic salt such as Na2C03 is added to the water solution, the tannins can react to form a salt. These salts are insoluble in organic solvents, such as chloroform or dichloromethane, but are soluble in water. 

While flowsheets are generally the same in principle in other plants, they frequently differ in details. For example, Crawford (30) describes a plant in which the extractors are spray towers, where the pyridine is continuously removed from a portion of the extracting solvent by an acid wash, and where CO2 or NaHCOs is used instead of H2SO4 to release the phenols from... 

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