Many bioactive compounds are non-polar molecules with low oral bioavailability due to their poor aqueous solubility and high melting point. It is therefore difficult to incorporate these compounds into foods due to their tendency to precipitate. Moreover, this kind of bioactive components can be effectively absorbed in the gastrointestinal tract only when they remain in soluble state within the food product during storage. In recent years, lipid-based delivery systems have been suggested as a convenient way of incorporating and protecting poorly water-soluble nutraceuticals in functional foods.
The purpose of this study was to investigate the potential for nanoemulsion-delivery systems to carry sylimarin, a complex mixture obtained from Silybum marianum [1]. Silymarin is composed of four flavonolignans isomers, among which sylibin is the major biologically active component and largely responsible for the well-documented antihepatotoxic activity. Even if pharmaceutical solutions are available as oral delivery means of silymarin [2, 3], its application as nutraceutical in functional foods is currently limited due to its poor water solubility as well as its high melting point.
In this study, the encapsulation efficiency of different carrier oils (sunflower oil, extra virgin olive oil, castor oil, flax seed oil) and emulsifiers (Tween 80, PGPR) was studied by determining silymarin solubility. Furthermore, the formation and stability of silymarin loaded nanoemulsions were evaluated. Results highlighted the critical role of the choice of carrier oil and emulsifier type in the attempt to obtain an efficient solubilisation of silymarin. Sylibin solubility increased with the increasing of the carrier polarity. The dipole-dipole interactions between polar groups of the carrier lipid and Sylimarin would favour the solubilisation of the bioactive molecule.
Knowledge gained from the current research could be used to develop effective delivery systems of silymarin as well as of other highly hydrophobic bioactive compounds into functional foods.
