Natural Terpenes as Penetration Enhancers for Transdermal Drug Delivery

Abstract

Abstract:The greatest hindrance for transdermal drug delivery (TDD) is the barrier property of skin, especially the stratum corneum (SC). Various methodologies have been investigated and developed to enhance the penetration of drugs through the skin. Among them, the most popular approach is the application of penetration enhancers (PEs), including natural terpenes, a very safe and effective class of PEs. In the present paper, we focused on terpenes as skin PEs for TDD. The mechanism of their action, the factors affecting their penetration enhancement effect, as well as their possible skin toxicity were discussed. Terpenes abundant in nature have great potential in the development of PEs. Compared to synthetic PEs, natural terpenes have been proved to possess higher enhancement activity. Interaction with SC intercellular lipids is the main mechanism of action for terpenes. The key factor affecting the enhancement effect is the lipophilicity of both terpenes and drug molecules. In addition, a lot of terpenes have also been proved to be much less toxic compared to azone, the classic synthetic PE. In summary, terpenes may be preferred over the chemically synthesized compounds as safe and effective PEs to promote the percutaneous absorption of drugs.

Natural Monoterpenes: Much More than Only a Scent

“…Today, it is known that terpenes, in comparison to synthetic permeation enhancers, can improve the barrier‐crossing activity of both lipophilic and hydrophilic compounds – even in low terpene concentrations . Kahraman et al .…”

Essential oil components and cytochrome P450 enzymes: a review

“…A great barrier for transdermal drug delivery is the stratum corneum , which is the outermost layer of the skin, and therefore natural or synthetic penetration enhancers are commonly used in pharmaceutical formulations. It is well documented that natural terpenes possess higher enhancement activity on the permeation of drugs through the skin, compared with synthetic penetration enhancers, and that natural terpenes are a very safe and effective class of penetration enhancers …”

“…It is well documented that natural terpenes possess higher enhancement activity on the permeation of drugs through the skin, compared with synthetic penetration enhancers, and that natural terpenes are a very safe and effective class of penetration enhancers. 38 In particular, extensive dermal application or the additional use of EOs, such as having an aroma bath, can lead to a relevant blood concentration of EO components. 37,39,40 Unfortunately, there are few experimental studies that deal with the human skin permeation behaviour of EO components.…”

Evaluation of Chemical Composition, Antibacterial, Antifungal, and Cytotoxic Activity of Laurus nobilis L Grown in Saudi Arabia

“…Most of the compounds like xylene, pinene, eugenol and terpeneine have shown antibacterial, and antifungal activity in previous reports. Monoterpenes hydrocarbons and oxygenated monoterpenes like α pinene and β-pinene, 3 carene, terpinene and Terpinyl acetate possess excellent antimicrobial 41,42 and anticancer properties 43 . Pinenes (α pinene and β-pinene) have shown antibacterial 43,44 antifungal 45 , antiviral46 and insecticidal properties 47 .…”