Nanocarriers: A Successful Tool to Increase Solubility, Stability and Optimise Bioefficacy of Natural Constituents.

Natural products are fascinating molecules in drug discovery for their exciting structure variability and also for their interaction with various targets. Drugs multi-targeting effect represents a more realistic approach to develop successful medications for many diseases. However, besides a large number of successful in vitro and in vivo studies, mostly of clinical trials fail. This is generally related to the scarce water solubility, low lipophilicity and inappropriate molecular size of natural compounds, which undergo structural instability in biological milieu, rapid clearance and high metabolic rate. Additionally, some molecules are destroyed in gastric juice or suffer to a massive pre-systemic metabolism in liver, when administered orally, limiting their clinical use. A reduced bioavailability can be also linked to drug distribution/accumulation in non-targeted tissues and organs that increase the side effects lowering the therapeutic efficacy and the patient compliance. Nanomedicine represents a favourable tool to increase bioavailability and activities of natural products. Generally, nanovectors provide large surface area, can overcome anatomic barriers. Each nanovector has its own advantages, disadvantages, and characteristics. In this review are reported different nanocarriers made of compounds which are Generally Recognized As Safe (GRAS) for the delivery of natural products, marketed as food supplements and medicines.