Quercetin (QUE) is a flavonol that has recently received great attention from the research community due to its important pharmacological properties. However, QUE’s low solubility and extended first-pass metabolism limit its oral administration. This review aims to present the potential of various nanoformulations in the development of QUE dosage forms for bioavailability enhancement. Advanced drug delivery nanosystems can be used for more efficient encapsulation, targeting, and controlled release of QUE. An overview of the primary nanosystem categories, formulation processes, and characterization techniques are described. In particular, lipid-based nanocarriers, such as liposomes, nanostructured-lipid carries, and solid-lipid nanoparticles, are widely used to improve QUE’s oral absorption and targeting, increase its antioxidant activity, and ensure sustained release. Moreover, polymer-based nanocarriers exhibit unique properties for the improvement of the Absorption, Distribution, Metabolism, Excretion, and Toxicology (ADME(T)) profile. Namely, micelles and hydrogels composed of natural or synthetic polymers have been applied in QUE formulations. Furthermore, cyclodextrin, niosomes, and nanoemulsions are proposed as formulation alternatives for administration via different routes. This comprehensive review provides insight into the role of advanced drug delivery nanosystems for the formulation and delivery of QUE.

Background: The genus Stachys L. (Lamiaceae) includes about 300 species as annual or perennial herbs or small shrubs, spread in temperate regions of Mediterranean, Asia, America and southern Africa. Several species of this genus are extensively used in various traditional medicines. They are consumed as herbal preparations for the treatment of stress, skin inflammations, gastrointestinal disorders, asthma and genital tumors. Previous studies have investigated the chemical constituents and the biological activities of these species. Thus, the present review compiles literature data on ethnomedicine, phytochemistry, pharmacological activities, clinical studies and the toxicity of genus Stachys. Methods: Comprehensive research of previously published literature was performed for studies on the traditional uses, bioactive compounds and pharmacological properties of the genus Stachys, using databases with different key search words. Results: This survey documented 60 Stachys species and 10 subspecies for their phytochemical profiles, including 254 chemical compounds and reported 19 species and 4 subspecies for their pharmacological properties. Furthermore, 25 species and 6 subspecies were found for their traditional uses. Conclusions: The present review highlights that Stachys spp. consist an important source of bioactive phytochemicals and exemplifies the uncharted territory of this genus for new research studies.