Improving on nature: The role of nanomedicine in the development of clinical natural drugs

Natural products have been used as a major source of drugs for millennia, and about half of the pharmaceuticals in use today are derived from natural products. However, their efficacy can be limited because of their low hydrophilicity and intrinsic dissolution rate(s), or physical/chemical instability. In addition, they can present scarce absorption, poor pharmacokinetics and bioavailability, little biodistribution, first pass metabolism, trivial penetration and accumulation in the organs of the body, low targeting efficacy. Novel nanoformulations based on drug delivery systems such as nanoparticles, micelles and vesicles, offer significant promise in overcoming these limitations. Nanomedicine results essential to develop appropriate therapeutic treatments of some essential drugs such as antitumor and antiparasistic agents (i.e. taxol, vincristine, camptothecin, doxorubicin, artemisinin, resveratrol, curcumin, salvianolic acid B, honokiol). The number of nanoformulations developed with flavonoids, in particular rutin, quercetin, silymarin, green tea catechins, is very high and a significant number of publications have also appeared concerning nanoformulations based on extracts and essential oils. So far, the studies obtained from the nanoencapsulated natural products are very encouraging, generally having a sustained release and improved bioavailability at much lower doses than conventional preparations, in many cases having a better safety profile.