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.
Compared with azone, the investigated EOs possess significantly higher penetration enhancement effect and lower skin toxicity. EOs can promote the skin permeation of ibuprofen mainly by disturbing rather than extracting the SC lipids.
The present study was conducted to evaluate and compare five essential oils (EOs) as penetration enhancers (PEs) to improve the transdermal drug delivery (TDD) of ibuprofen to treat dysmenorrhoea. The EOs were prepared using the steam distillation method and their chemical compositions were identified by GC-MS. The corresponding cytotoxicities were evaluated in epidermal keartinocyte HaCaT cell lines by an MTT assay. Furthermore, the percutaneous permeation studies were carried out to compare the permeation enhancement effect of EOs. Then the therapeutic efficacy of ibuprofen with EOs was evaluated using dysmenorrheal model mice. The data supports a decreasing trend of skin cell viability in which Clove oil >Angelica oil > Chuanxiong oil > Cyperus oil > Cinnamon oil >> Azone. Chuanxiong oil and Angelica oil had been proved to possess a significant permeation enhancement for TDD of ibuprofen. More importantly, the pain inhibitory intensity of ibuprofen hydrogel was demonstrated to be greater with Chuanxiong oil when compared to ibuprofen without EOs (p < 0.05). The contents of calcium ion and OPEN ACCESSMolecules 2015, 20 18220 nitric oxide (NO) were also significantly changed after the addition of Chuanxiong oil (p < 0.05). In summary, we suggest that Chuanxiong oil should be viewed as the best PE for TDD of ibuprofen to treat dysmenorrhea.
A prerequisite for successful transdermal or dermal drug therapy is the drug ability to penetration through the skin, especially stratum corneum (SC). The most acceptable technique for measuring skin permeation in vitro is the application of both the Franz diffusion cell device and the skin model. In the skin model, a liposome-based artificial skin membrane (LASM) consisting of tight layers of liposomes immobilized on a filter was prepared and characterized. Using porcine ear skin, rat skin and Strat-M™ artificial membrane as control, the LASM was then evaluated in permeation studies with five active compounds: ferulic acid, paeoniflorin, albiflorin, tetrahydrocolumbamine, and tetrahydropalmatine. The scanning electron microscope images demonstrated complete filling of the membrane pores with lipids and the formation of a continuous liposomal coating. The contents of egg phosphatidylcholine (EPC) and cholesterol in LASM were measured to be 12.08 ± 0.18 and 4.41 ± 0.04 mg/cm, respectively. Moreover, revealed by the measurement of electrical resistance, the LASM remains intact for at least 12 h with the incubation of 20% ethanol. The results of permeation studies demonstrated a good correlation (r= 0.9743, r = 0.9871) of P values between the drugs' permeation through LASM and porcine ear skin. In addition, by ATR-FTIR analysis, a slighter shift of CH stretching frequency between LASM and porcine ear skin was observed compared with the shift between Strat-M™ membrane and porcine ear skin. In summary, for the first time, the LASM has been proved to be a valuable alternative to porcine ear skin in permeation studies using Franz diffusion cell device.
The results of previous studies showed potential correlations between the penetration enhancement effect of essential oils and the drug properties of traditional Chinese medicine based on the data mining method. As chemical composition is the material basis of drug properties of traditional Chinese medicine, this article further analyzed the correlation between the chemical composition of essential oils and the drug properties. Firstly, essential oils were extracted by steam distillation, and then physicochemical parameters of essential oils, such as relative density and refractive index, were measured. The chemical components of 20 essential oils were analyzed by GC-MS, and divided into 12 categories according to skeleton features and functional groups. Finally, Logistic regression analysis was applied to reveal the correlations. The results proved that five flavors, four tastes and channel tropisms showed the correlation with chemical composition of essential oils (P<0.05). In conclusion, there were obvious correlations and regularity between the drug properties of traditional Chinese medicine and the chemical composition of essential oils.
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