Surface Activity and Emulsification Properties of Saponins as Biosurfactants

Saponins are group of chemical compounds found in many plants and some marine animals. Due to extensive biological activity, these compounds are widely used in pharmaceutical, food, cosmetic, and many other industries. Saponins are also known as biosurfactants. The word saponin implies a latin word “sapo” which means soap. Saponins are amphiphilic compounds containing hydrophilic and hydrophobic properties. One of the important characteristics of saponins is the foaming properties which makes them able to act as surface-active agents. Surface-active agents are widely used chemicals in different industrial processes. The purified Quillaja Saponin (QS-21) as a representative of plant saponins with high surface activity and biological properties has been proposed for industrial application as biosurfactant. This property of QS-21 is due to its high hydrophilic-lipophilic balance (HLB) value and lengthy sugar side chain. Formation of nanoemulsions using QS-21 saponin as biosurfactant has achieved more interest in recent studies. This chapter focused on saponin structure, surface activity, critical micelle concentration (CMC), rule of saponins as biosurfactants, and stabilization of nanoemulsions via saponin. The chapter also reviewed the Quillaja Saponin (QS-21) isolated from the bark of Quillaja saponaria Molina as a biosurfactant. It is expected that the future application of biosurfactants based on natural and less toxic bio-sources would become a topic of interest in food, cosmetic and pharmaceutical companies. However, further research should be carried out to highlight all the safety and side effects of saponin-based biosurfactants in future markets.