Herbal nano-formulations for topical delivery

The use of herbal medicines has gained popularity throughout the world in recent times. Often seen as natural alternatives with fewer side-effects than synthetic medicines, these medicinal plants and their phytochemical constituents are thought to have potential applications in the management of a wide range of health conditions. As such, many whole herbal preparations, herbal extracts and isolated phytocontituents have been subjected to pharmacological and clinical research, in which the in vitro demonstrated benefits of the phytochemical constituents do not always translate directly to in vivo and clinically demonstrated benefits. This has highlighted issues such as poor bioavailability, stability and distribution of herbal medicines when administered in traditional dosage forms and paved the way for research into the incorporation of herbal medicines into novel drug delivery systems. Nanotechnology is one of the key novel drug delivery methods under investigation, with nanoformulations thought to have a wide variety of benefits in comparison with conventional preparations of plant constituents, which include enhanced permeability, solubility, bioavailability, therapeutic activity, stability, improved distribution within tissues and sustained delivery. The present review examines the available research into the use of nanoformulations in the topical delivery of herbal medicines. It identifies the various nanoformulation approaches that have been developed and successfully used as a means to enhance the topical delivery of natural bioactives, including nanoemulsions, liposomes, phytosomes, microspheres, transferosomes. The review also highlights the pressing need for safety considerations and validated toxicity guidelines in the development of such novel drug delivery systems.