Formulation of plumbagin-loaded microemulsion: Evaluation of anti-rheumatoid efficacy in Wistar rat model

Rheumatoid arthritis has become a common disease among the elderly. Plumbagin, a plant-derived chemical, has been shown to lower the levels of proinflammatory cytokines and interleukins linked to rheumatoid arthritis progression. The objective of the present research work was to assess the anti-arthritic activity of plumbagin-loaded microemulsion in CFA (Complete Freund's Adjuvant) induced arthritic rats. The plumbagin-loaded microemulsion was formulated with Captex 300 as oil phase, Tween 80, and Transcutol as surfactant mixture. The microemulsion system was analyzed for its physical appearance, pH, conductivity, zeta potential, globule size, compatibility, viscosity, drug content, and drug release rate. Formulation (F1P) with 0.5 % plumbagin, 8 % oil, 40 % Smix and 52% water was selected as optimized formulation. The optimized formulation exhibited highest drug content (89.2%), in vitro release rate (87.36%) and lowest viscosity value (8.12 cP). Solubility of plumbagin in microemulsion was enhanced up to 24.38 times as compared to water. Upon intraperitoneal administration, plumbagin-loaded microemulsion remarkably reduced the concentration of proinflammatory cytokines (TNF‐α, IL‐6, IL‐β, IL-10), liver marker enzymes (SGPT, SGOT, ALP) and restored the level of serum antioxidants (CAT, SOD, GSH) as compared to pure plumbagin in arthritic rat model. The data suggest an improved solubility of plumbagin by microemulsion system, which may lead to a reduced dose and better therapeutic outcomes.