Nano- and Microsized Forms of Silymarin and Silybin

Modern preparations of milk thistle have been used since 1960−1970s. By their chemical nature, the active substances of milk thistle are flavonoids (flavonolignans). The preparations used are both the milk thistle flavonolignan complex (silymarin) and the most active individual substance (silybin). Preparations based on silymarin and silybin are in demand in clinical practice as hepatoprotectors; however, their serious drawbacks are low water solubility and bioavailability, which significantly reduces their therapeutic potential. In this regard, nano- and microforms of silymarin/silybin are being actively developed. The review provides information on the sources of obtaining, chemical structure, and biological activity of silymarin and silybin. The main known nano- and microforms of silymarin and silybin are considered, and the methods for their obtaining are described. These forms are obtained using one or a combination of several technological methods: dispersion, dissolution in suitable solvents, formation of inclusion complexes and solid dispersions, chemical modification, etc. The developed forms of silymarin/silybin are nanocrystals, solid dispersions, solid lipid systems, inclusion complexes, dendrisomes, liposomes, nano- and microemulsions, polymer particles, and nanocomposites. Each of these forms has a number of advantages, which, in general, include an increase in the solubility and bioavailability of silybin, prolonged/controlled release from nano- and microstructures, and an increase in stability. The development of nano- and microforms of silymarin and silybin made it possible to obtain compositions with improved physicochemical characteristics and biopharmaceutical properties, as well as a higher specific activity (including hepatoprotective, antitumor, antiviral, and antimicrobial activity), which gives grounds for expanding the therapeutic range of ​​application of drugs of this group.