Phosphate buffer.

  The present research has been undertaken with the aim to formulate and evaluate the herbal gel containing Calophyllum inophyllum extract. The gel formulation was designed by using methanol extract of Calophyllum inophyllum stem barks in concentration (5%) and evaluated using physiological measurements. The gel was prepared by using accurately weighted amount of drug along with other additives were poured into the fixed amount of hydrated Carbopol-934 dispersion with constant stirring. Finally the required amount of 0.5M sodium hydroxide solution was added to induce gelation. All the prepared gel formulations were subjected for preliminary evaluation such as pH, Viscosity and Rheological studies, Spreadability, Drug content uniformity, Skin irritation test, In vitro diffusion study, In vitro permeation studies, Drug Polymer Compatibility Studies. The optimized herbal gel formulation of the drug was subjected to accelerated stability studies at both 40C and 370C for about 3 months. A suitable UV method was developed for herbal gel formulation by using Phosphate buffer 6.8 as solvent and lmax found to be 284 nm. The pH of all the formulations was in the range of 6.63 to 7.35, which lies in the normal pH range of the skin. The drug content was in the range of 96.6 to 99.5 %. The formulations did not produce any skin irritation, i.e., erythema and edema for about a week, when applied over the skin. The drug interaction FT-IR studies indicated that there was no chemical interaction between the drug and the polymers used in gel formulations.   Key Words: Calophyllum inophyllum, Methanolic extract, Herbal gel formulations, Carbopol 934, pH, Phosphate buffer.