**4.1 Soybean phosphatidylcholine (SPC)**

### **4.1.1 Organic solvent extraction**

Fractions in soybean phospholipids are isolated due to their solubilities' differences in organic solvents. PC exhibits large solubility in lower alcohol (C1-C4) whereas PE and PI have small solubilities. PC- and PI-enriched products can be obtained by their solubilities' difference. When treated with lower alcohol, PC in deoiled phospholipids is soluble in alcohol leaving insoluble matter consisting mainly of PE and PI. The ratio of PC to PE increases from 1:1 (w/w) in raw material to 3:1 (w/w), and even to 12:1 (61% PC, 5% PE).

Better isolation effect on PC can be obtained by isopropanol. Mixtures of high-purity phospholipids and isopropanol with the ratios of 8:157-16:157 (12:157 is optimal) is added into the agitated- and refluxed-closed container. The extraction is conducted in thermostatic water bath or cryohydrate bath with isopropanol volume fraction of 95%-100% (100% is optimal) at -5-15 degrees Celsius (-5 degrees Celsius is optimal) for 5min-11min (5min is optimal). After the extraction, the mixture is filtered, evaporated to remove isopropanol and dried to obtain product with mass fraction of PC increased from 25.6% in raw material to 66.8%. Isopropanol extraction is the most commonly employed step to obtain high PCcontaining phospholipids from deoiled phospholipids (An et al, 2001).

#### **4.1.2 Lower alcohol with salt or acid extraction**

It's also an effective method to fractionate phospholipids with the property that phospholipids can react with some salts or acids and precipitate. This method is more promising than organic solvent extraction as metal ions or acids can 'recognize' phospholipids molecules more effectively than solvents.

100g of phospholipids containing 45% PC is dissolved in 1L ethanol of 95% before addition of 4.5g of zinc chloride. The light yellow phospholipid-zinc chloride compound precipitate formed is centrifuged, decomposed with 250ml freezed acetone under nitrogen to obtain 36.7g of phospholipids containing 99.6% PC (Ni, 1995).
