Cyclodextrins as an encapsulation molecular strategy for volatile organic compounds- Pharmaceutical applications

The use of essential oils has gained importance due to their wide range of biological properties. Essential oils comprise a complex mixture of volatile organic compounds (VOCs), so the study of VOCs as active pharmaceutical ingredients is often more precise and fruitful. VOCs are natural origin molecules that constitute a sustainable alternative to synthetic drugs due to their important therapeutic value. However, VOCs possess poor solubility in aqueous solutions, high volatility, and, consequently, low stability and bioavailability, limiting VOC handling in industry and their potential use in therapeutics, despite their promising biological properties. Thereby, cyclodextrins (CDs) have emerged as suitable carriers of VOCs, giving rise to so-called VOC/CD inclusion complexes. CDs constitute an inexpensive viable solution for encapsulating VOCs to improve their properties, namely their apparent solubility and stability toward pH, light, and temperature. This review provides a conceptual framework of several VOC/CD inclusion complexes developed. In addition, the most exploited preparation techniques and their influence on the values of encapsulation efficiency and formation constant (K_f) are highlighted. The most recent in vitro or in vivo biological experiments regarding VOC/CD inclusion complexes in the development of pharmaceutical products are also presented. Finally, the toxicological, and regulatory aspects are discussed.