Formulation and evaluation of microemulsion gel containing Boswellia serrata and Primrose oil for Arthritis

Osteoarthritis and rheumatoid arthritis are two inflammatory joint conditions that lead to degeneration of the synovial region leading to pain and deterioration of the joints finally culminating into loss of joint function. Natural herbal extracts like Boswellia serrata have been found to contain components like Boswellic acids which exhibit the property of inhibition of certain enzymes which are mediators of inflammation in the tissue region. These active components aid to inhibit enzymes like 5-Lipoxygenase (5-LO) and 5-Hydroxyeicosatetraenoic acid (5-HETE) thus inhibiting the inflammation component of joint damage. The poor aqueous solubility of the extract of Boswellia serrata poses a challenge for designing effective dosage forms for administering the boswellic acid enriched extract to the site of action. The present work comprises of formulation of a clear isotropic microemulsion system and microemulsion gel containing solubilized Boswellia serrata extract and Primrose oil. The microemulsion was evaluated for globule size, Fourier transform infrared spectroscopy, entrapment efficiency, stability and irritation potential by HETCAM assay whereas the microemulsion gel was evaluated for pH, viscosity and irritation potential. The microemulsion was found to exhibit a globule size of 403.1 nm,  no changes in chemical structure, entrapment efficiency of 91 % and stable at all conditions of temperatures of 25°C,  30°C  and 40°C, light, freeze-thaw, centrifugation test and non-irritant in nature. The microemulsion gel was found to have a pH of 5.5, viscosity of and non-irritant by HETCAM assay.