Transdermal microemulsions of Boswellia carterii Bird: formulation, characterization and in vivo evaluation of anti-inflammatory activity

Context: Boswellia species are trees (family: Bruseraceae) found in India, Northern Africa and the Middle East. Objective: This study aims at formulating low dose biologically active fraction from the oleogum resin of Boswellia carter)) (BC) in transdermal (TD) microemulsions (MEs) to acquire promoted anti-inflammatory efficacy. Materials and methods: The bioactive fraction of the oleogum resin of BC was tested for solubility in different components. The most efficient were selected for constructing phase diagrams for ME preparation. The bioactive fraction was assayed by high performance liquid chromatography for 3-acetyl-11-keto-beta-boswellic acid (AKBA), at 210 nm. The bioactive fraction was incorporated in 6 MEs. ME systems were evaluated for drug content and optimized systems were tested for characterization, permeation, skin irritancy and in vivo evaluation of anti-inflammatory activity. Results and Discussion: Two systems were selected; ME1 and ME4 composed of Tween 80: PEG 400 at 1:1 and 2:1 ratio, with oil content 7.78 and 17.5%, respectively. The systems showed high encapsulation efficiency >83%, small droplet size <100 nm, and suitable pH for topical application. Permeation parameters for ME1 were higher compared to ME4. Both MEs were non irritant. ME1 showed significantly higher anti-inflammatory activity versus the standard TD anti-inflammatory piroxicam. Conclusions: Optimized TD BC MEs could be used as a safe, effective and long acting alternative to oral anti-inflammatories, providing higher and prolonged efficacy and better patient compliance.