Natural Terpenes as Penetration Enhancers for Transdermal Drug Delivery.

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.

[Evaluation of pharmacokinetics and in vitro/in vivo correlation of ibuprofen with essential oils as penetration enhancer following transdermal administration].

The study was carried out to investigate the pharmacokinetics and in vitro/in vivo correlation of ibuprofen with essential oils as penetration enhancers (PE) following transdermal administration. With Azone as the positive control, ibuprofen hydrogels containing Chuanxiong oil, Angelica oil or Cinnamon oil as PE were prepared and administered to the rat abdominal skin. Then the pharmacokinetics of ibuprofen following transdermal administration were investigated and compared. In comparison with negative control (no PE was added), the relative bioavailability values with the addition of Chuanxiong oil, Angelica oil, Cinnamon oil and Azone as PE were determined to be 161.87%, 171.05%, 151.37% and 148.66%, respectively. In vitro/in vivo correlation analysis was performed by deconvolution method and the results demonstrated a good correlation between in vitro and in vivo percutaneous absorption studies. The correlation coefficients were measured to be 0.999 7, 0.995 2 and 0.999 4 for Chuanxiong oil, Angelica oil and Cinnamon oil respectively. In summary, Chuanxiong oil, Angelica oil and Cinnamon oil as PE could significantly enhance the bioavailability of ibuprofen following transdermal administration. A satisfactory in vitro/in vivo correlation could be obtained by using hydrogel as the dosage form.

[Association between chemical composition of essential oil with penetration enhancement effect and drug properties of traditional Chinese medicine].

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.

Potential of Essential Oils as Penetration Enhancers for Transdermal Administration of Ibuprofen to Treat Dysmenorrhoea.

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 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.

[Association between penetration enhancement effect of essential oils and drug properties of traditional Chinese medicines by data mining method].

To study the association between penetration enhancement effect of essential oils and drug properties of traditional Chinese medicines. Through literature research, 34 kinds of essential oils with the penetration enhancement effect were collected. The methods of frequency analysis and variable crosstab were used for intuitive analysis and association analysis. The association between penetration enhancement effect of essential oils and drug properties (four natures, five flavors, channel tropism) were analyzed by a general linear model. According to the findings, the essential oils with penetration enhancement effect were all sourced from acrid traditional Chinese medicines, because their positive drug nature contributed to the enhancement of the penetration effect of essential oil; five flavors had little effect on penetration enhancement (P = 0.6982), but four natures and channel tropism showed significant effects (P = 0.011, 0.077). In conclusion, there were obvious association and regularity between penetration enhancement effect of essential oils and drug properties of traditional Chinese medicine.