Enhancing Effect of Chiral Enhancer Linalool on Skin Permeation of Naproxen.

OBJECTIVE: To investigate the permeation-enhancing effect of dl-linalool, d-linalool, and l-linalool on model drugs across excised rat skin and the effect of linalool on the ceramides in stratum corneum lipids. METHODS: In vitro skin permeation studies were performed with Valia-Chien diffusion cells, and the permeation samples were analyzed by high performance liquid chromatography with chiral stationary phase. Infrared spectroscopy was used to investigate the effect of linalool on stratum corneum lipids. RESULTS: When the donor vehicles added with 1% dl-linalool, 1% d-linalool, or 1% l-linalool, the steady-state skin permeation rate of naproxen was (2.47±0.63), (1.53±0.54), (1.73±0.48) µg·cm(-2)·h(-1), respectively, which is 2.49, 1.55, and 1.75 times (all P<0.05) compared with control group [(0.99±0.42)µg·cm(-2)·h(-1)], and the differences were statistically significant (all P<0.05). The permeation-enhancing effect of dl-linalool on naproxen was found significantly greater than that of d-linalool and l-linalool (both P<0.05). Compared with the control group, the stratum corneum treated with dl-linalool shifted to higher wave number on 2.09 cm(-1) of asymmetric CH2 stretching vibrations in attenuated total reflection-fourier transform infrared spectroscopy analysis. However, stratum corneum treated with d-linalool and l-linalool did not display this phenomenon. CONCLUSION: The disturbing degree of dl-linalool on stratum corneum lipids (ceramides) is different from that of linalool enantiomers, suggesting their different enhancing effect on the same drug.

[The potential effects of linalool on enantioselective skin permeation of norgestrel].

The purpose of this study is to investigate the enantioselectivity of norgestrel (NG) transdermal permeation and the potential influence of linalool and lipids on the enantioselectivity. In vitro skin permeation studies of NG across the excised rat skins were performed with Valia-Chien diffusion cells, and the permeation samples were analyzed by enantioselective HPLC. The possible enantioselective permeation of NG across intact rat back skin and lipids extracted rat back skin and the influence of linalool were evaluated. The skin permeation rate of dl-NG was two times higher than that of l-NG when donor solutions (EtOH/H2O 2 : 8, v/v) containing l-NG or dl-NG. It may be mainly attributed to the solubility discrepancy between enantiomer and racemate. The enantioselective permeation of dl-NG across intact rat skin was observed when the donor solutions containing dl-linalool. The permeation flux of l-NG was 22% higher than that of d-NG. But interestingly, the enantioselective permeation of dl-NG disappeared under the same experimental condition except that the lipid extracted rat skin was used. Attenuated total reflection-fourier transform infrared spectroscopy analysis of stratum corneum showed that the wave number for asymmetric CH2 stretching vibrations of lipids treated with dl-linalool was greater than that of the control. The results indicated that the enantioselective permeation of NG may be contributed by the interaction between dl-linalool and lipids. More than half of lipids were composed of ceramides. The stereospecific interaction maybe existed among chiral enhancer (linalool), lipids (ceramides) and/or chiral drugs (NG).

[Cloning, expression and functional identification of a type III polyketide synthase gene from Huperzia serrata].

A cDNA encoding novel type III polyketide synthase (PKS) was cloned and sequenced from young leaves of Chinese club moss Huperzia serrata (Thunb.) Trev. by RT-PCR using degenerated primers based on the conserved sequences of known CHSs, and named as H. serrata PKS2. The terminal sequences of cDNA were obtained by the 3'- and 5'-RACE method. The full-length cDNA of H. serrata PKS2 contained a 1212 bp open reading frame encoding a 46.4 kDa protein with 404 amino acids. The deduced amino acid sequence of H. serrata PKS2 showed 50%-66% identities to those of other chalcone synthase super family enzymes of plant origin. The recombinant H. serrata PKS2 was functionally expressed in Escherichia coli with an additional hexahistidine tag at the N-terminus and showed unusually versatile catalytic potency to produce various aromatic tetraketides, including chalcones, benzophenones, phloroglucinols, and acridones. In particular, the enzyme accepted bulky starter substrates N-methylanthraniloyl-CoA, and carried out three condensations with malonyl-CoA to produce 1, 3-dihydroxy-N-methylacridone. Interestingly, H. serrata PKS2 lacks most of the consensus active site sequences with acridone synthase from Ruta graveolens (Rutaceae).