Nano emulsions stabilized by natural emulsifiers: A comprehensive review on feasibility, stability and bio-applicability

Nano emulsions (NEs) stabilized by synthetic emulsifiers have shown proficiency in tailoring various commercial products that encompass food, pharmaceutical, and cosmeceutical industries. NEs have also become an integral part in modern drug delivery due to their ability to enhance activity and biocompatibility of polar as well as non-polar bioactive compounds. However, extensive utilization of synthetic emulsifiers in their production has alarmed the mass consumers for their adverse health and environmental effects. There have been increasing demands among consumers for products that are sustainable, biologically, and environmentally benign. Natural emulsifiers like phospholipids, proteins, biosurfactants, saponins, and polysaccharides have been proven in many of the recent studies to be competent enough with their synthetic counterparts in the formulation of NEs. Apart from the ability to produce NEs that show decent stability profiles under wide ranges of environmental stresses, these emulsifiers are very safe to consume, biocompatible, biodegradable, and environmentally friendly. In this article, recent developments on the formulations of NEs using different natural emulsifiers including their origin, production, emulsifying action, and comparative performance with synthetic emulsifiers, along with stability profile of NEs upon environmental stresses, biological importance, and future prospects have been discussed.