Background: Astilbin is a promising candidate drug for psoriasis. However, the poor solubility and stability limited its clinical application. Purpose: The present work aimed to develop a stable microemulsion of astilbin formulation and evaluate its effect in vitro and in vivo. Methods: Oil phase, surfactants, and cosurfactants were screened using solubility and stability of astilbin as the index. The central composite experiment design and response surface methodology analysis were adopted to optimize microemulsion parameters. The particle size, zeta potential, polydispersity index, viscosity, drug content, encapsulation, transmission electron microscopy (TEM), and stability of the optimized microemulsion were evaluated. Then, the drug release and anti-psoriasis effects were evaluated in a mouse model induced by imiquimod. Results: The optimum formulation contained Labrafil M 1944 Cs (10.12%), Polyoxyethylene Castor Oil 35 (37.41%), propylene glycol (12.47%), water (40%), and gallic acid (2.9%), and the average particle size was 14.71 nm. The permeability of astilbin from the optimized astilbin-gallic acid microemulsion in 24 hr was 4.39 times higher compared with the astilbin’s microemulsion. The content of astilbin in astilbin-gallic acid microemulsion remained unchanged after being stored at 25°C for 4 months compared with astilbin aqueous (3 h) and astilbin microemulsion (185 h). Compared with the model group, the optimized formulation decreased the PASI score and Baker score by 49% and 73%, respectively, which showed a favorable anti-psoriasis effect. Moreover, there was no difference in the anti-psoriasis effect between the optimized group and the positive control. Conclusion: These results indicated that the astilbin-gallic acid microemulsion might be a potential topical drug used for the treatment of psoriasis.

中文翻译：

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优化落新妇苷微乳透皮给药系统，提高稳定性和抗银屑病活性

背景：落新妇苷是一种很有前途的银屑病候选药物。但溶解性和稳定性较差，限制了其临床应用。目的：目前的工作旨在开发一种稳定的落新妇苷微乳制剂并评估其体外和体内效果。方法：以落新妇苷的溶解度和稳定性为指标，筛选油相、表面活性剂和助表面活性剂。采用中心复合实验设计和响应面法分析优化微乳液参数。对优化微乳液的粒径、zeta 电位、多分散指数、粘度、药物含量、包封、透射电子显微镜 (TEM) 和稳定性进行了评估。然后，在咪喹莫特诱导的小鼠模型中评估药物释放和抗银屑病作用。结果：最佳配方为Labrafil M 1944 Cs（10.12%）、聚氧乙烯蓖麻油35（37.41%）、丙二醇（12.47%）、水（40%）和没食子酸（2.9%），平均粒径为14.71纳米。优化后的落新妇苷-没食子酸微乳中落新妇苷的渗透性在24 小时内是落新妇苷微乳的4.39 倍。与落新妇苷水溶液（3 h）和落新妇苷微乳（185 h）相比，落新妇苷-没食子酸微乳中落新妇苷含量在 25℃ 下保存 4 个月后基本保持不变。与模型组相比，优化后的处方组PASI评分和Baker评分分别降低了49%和73%，具有良好的抗银屑病作用。而且，优化组与阳性对照之间的抗银屑病作用没有差异。