Formulation of Gel Containing Phenylbutenoid Extract for Pain Relief

Objective: A phenylbutenoid extract (PE) was obtained from Zingiber cassumunar rhizomes. Phenylbutenoids; namely DMPBD, compound D, and compound D acetate, have been identified as major anti-inflammatory and analgesic constituents. This present study aimed to formulate a gel containing PE that could be used as an alternative ultrasound gel for acute or chronic inflammatory treatment. Material and Methods: Gel formulations containing 0.5, 1, and 2% w/w PE were prepared using Carbopol 934 and hydroxyethylcellulose (HEC 4,000) as gelling agents. The contents of phenylbutenoids were quantified by a high-performance liquid chromatography (HPLC). PE gels were studied on physicochemical properties and accelerated stability tests. The PE gels, F2 and F5, were used to evaluate the release of phenylbutenoids using a modified Franz diffusion cell. In the skin permeation study, the 2% PE gels were applied either with or without a 0.8 W/cm2 intensity ultrasound for 2, 5, and 10 min. Results: Based on physicochemical properties and accelerated stability tests, F2 and F5 formulations showed good stability. The release kinetics of 0.5% and 1% and 2% w/w PE of both formulations were best fit to Higuchi’s model and zero-order model, respectively. In the skin permeation study, PE gel combined with ultrasound application for 2 min exhibited higher phenylbutenoids in the skin and also a shorter lag time than PE gel application alone. Conclusion: The gel containing 2% w/w phenylbutenoid extract was suggested as an alternative ultrasound gel containing an anti-inflammatory agent for the treatment of musculoskeletal disorders in phonophoresis.