**5. Phospholipids: creating the structural framework for novel drug delivery systems**

These are complex substance having chemical, biochemical and nutritional characteristics by which they can distinguish as placed in a unique nutritional category. They are complex lipid molecules important for life and are found in all human and the other known structure to make cell membranes. The biochemical importance of phospholipids is reflected in their extraordinary clinical benefits as dietary supplements. The phospholipids are readily compatible with the entire range of vitamins, minerals, metabolites and herbal preparations. The dietary phospholipids and omega-3 fatty acid works in functional synergy in cell membranes. Phosphatidylcholine is a bi-functional compound miscible both in water and in oil environments, and is well absorbed when taken by mouth. Phosphatidylcholine is not merely a passive "carrier" for the bioactive compounds, but is itself a bioactive nutrient with documented clinical efficacy for liver disease (including alcoholic hepatitis). Phosphatidylcholine is present in egg yolk, brain tissue and a wide

#### **Figure 4.**

*Cell membranes are largely lipid phase. A double molecular layer consisting of PC and other phospholipids provides a continuous matrix into which the proteins insert [31].*

variety of animal fat and plant oils. It is routinely present in the bile fluid, to help emulsify food ingredient for absorption [31] (**Figure 4**).

A number of drug delivery system is based entirely on Phosphatidylcholine such as liposomes, ethosomes, phytosomes, transferosomes, and nanocochhelates. The hydrophilic and hydrophobic domain/segment within the molecular geometry of amphiphilic lipids orient and self-organize in ordered supramolecular structure when confronted with solvents. Some commonly used synthetic phospholipids are dioleoyl-phosphatidyl-choline (DOPC), dioleoyl-phosphatidyl-ethanolamine (DOPE), distearoyl-phosphatidyl-choline (DSPC), and distearoyl-phosphatidylethanolamine (DSPE) [31].
