Essential oils are complex blends of a variety of volatile molecules such as terpenoids, phenol-derived aromatic components, and aliphatic components having a strong interest in pharmaceutical, sanitary, cosmetic, agricultural, and food industries. Since the middle ages, essential oils have been widely used for bactericidal, virucidal, fungicidal, antiparasitical, insecticidal, and other medicinal properties such as analgesic, sedative, anti-inflammatory, spasmolytic, and locally anaesthetic remedies. In this review their nanoencapsulation in drug delivery systems has been proposed for their capability of decreasing volatility, improving the stability, water solubility, and efficacy of essential oil-based formulations, by maintenance of therapeutic efficacy. Two categories of nanocarriers can be proposed: polymeric nanoparticulate formulations, extensively studied with significant improvement of the essential oil antimicrobial activity, and lipid carriers, including liposomes, solid lipid nanoparticles, nanostructured lipid particles, and nano- and microemulsions. Furthermore, molecular complexes such as cyclodextrin inclusion complexes also represent a valid strategy to increase water solubility and stability and bioavailability and decrease volatility of essential oils.

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, scarce biodistribution, first-pass metabolism, trivial penetration and accumulation in the organs of the body, or low targeting efficacy. Novel nanoformulations based on drug delivery systems, namely nanoparticles, micelles, and vesicles, offer significant promise in overcoming these limitations. Nowadays, nanomedicine is crucial in developing appropriate therapeutic treatments of essential drugs, specifically antitumor and antiparasistic agents (i.e., Taxol, vincristine, camptothecin, doxorubicin, artemisinin) and other emerging molecules with pleiotropic functions (i.e., resveratrol, curcumin, salvianolic acid B, honokiol). Additionally, the number of nanoformulations developed with flavonoids, in particular rutin, quercetin, silymarin, and green tea catechins, is constantly increasing, and a significant number of publications have appeared in the last decade pertaining to nanoformulations based on extracts and essential oils. Most of these studies report very promising nanoformulations with sustained release and improved bioavailability at much lower doses than conventional preparations, and in many cases, also a better safety profile.

Artemisia annua L. (Asteraceae) is native to China, now naturalised in many other countries, well known as the source of the unique sesquiterpene endoperoxide lactone artemisinin, and used in the treatment of the chloroquine-resistant and cerebral malaria. The essential oil is rich in mono- and sesquiterpenes and represents a by-product with medicinal properties. Besides significant variations in its percentage and composition have been reported (major constituents can be camphor (up to 48%), germacrene D (up to 18.9%), artemisia ketone (up to 68%), and 1,8 cineole (up to 51.5%)), the oil has been subjected to numerous studies supporting exciting antibacterial and antifungal activities. Both gram-positive bacteria (Enterococcus, Streptococcus, Staphylococcus, Bacillus, and Listeria spp.), and gram-negative bacteria (Escherichia, Shigella, Salmonella, Haemophilus, Klebsiella, and Pseudomonas spp.) and other microorganisms (Candida, Saccharomyces, and Aspergillus spp.) have been investigated. However, the experimental studies performed to date used different methods and diverse microorganisms; as a consequence, a comparative analysis on a quantitative basis is very difficult. The aim of this review is to sum up data on antimicrobial activity of A. annua essential oil and its major components to facilitate future approach of microbiological studies in this field.

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Flavonoids are among the biggest group of polyphenols, widely distributed in plant-based foods. A plethora of evidence supports the health benefits and value of flavonoids can play in the physiological function treatment and in the prevention of disease particularly in the prevention of degenerative conditions including cancers, cardiovascular and neurodegenerative diseases. Hence, flavonoids represent the active constituents of many dietary supplements and herbal remedies, as well as there is an increasing interest in this class of polyphenols as functional ingredients of beverages, food grains and dairy products. Conversely, various studies have also shown that flavonoids have some drawbacks after oral administration such as stability, bioavailability and bioefficacy. This article reviews the current status of novel nanodelivery systems including nanospheres, nanocaspsules, micro-and nanoemulsions, micelles, solid lipid nanoparticles and nanostructured lipid capsules, successfully developed for overcoming the delivery challenges of flavonoids.

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Artemisinin (qinghaosu), a unique endoperoxide sesquiterpene lactone isolated from Artemisia annua L., is a very active antimalarial drug, including severe and cerebral malaria. However, its therapeutical efficacy is limited due to its scarce bioavailability. In this article, artemisinin-loaded conventional and polyethylene glycol (PEGylated) liposomes were proposed as carriers to increase biopharmaceutical properties of the drug. Encapsulation efficacy was determined by high-performance liquid chromatography/diode array detection/electrospray ionization-mass spectrometry, dimensional analysis was performed by dynamic light scattering, and morphology was performed by trasmission electron microscopy. After dialysis, both liposomal formulations showed an encapsulation efficacy of more than 70%; mean diameter of all the artemisinin-loaded vesicles was approximately 130-140 nm. The polydispersity index of the formulations ranged from 0.2 to 0.3 and resulted as suitable for intraperitoneal (i.p.) administration. Pharmacokinetic profile and the main pharmacokinetic parameters of the carriers were evaluated in healthy mice i.p. Free artemisinin was rapidly cleared from plasma and hardly detected 1 hour after administration. Conversely, both liposomal formulations showed much longer blood-circulation time than free artemisinin; artemisinin was still detectable after 3 and 24 hours of administration, respectively, for conventional and PEGylated liposomes. AUC(0-24 h) values were increased by approximately 6 times in both of the liposomal formulations, in comparison with free artemisinin. A strong effect of formulation on the half-life of artemisinin was enhanced by more than 5-fold by the incorporation of PEG into liposomes. Liposomes loaded with artemisinin, especially the long-circulating vesicles, could really represent a new strategy for developing smart, well-tolerated, and efficacious therapeutic nanocarriers to treat tumors, but could also be very useful to treat parasitic disease.