Colon Targeted Prodrug Approach

Nalidixic acid-Tryptophan conjugate was synthesized by coupling Nalidixic acid with glycine methyl ester hydrochloride and characterized by melting point, thin layer chromatography, RM value, scanning electron microscopy, x-ray diffraction study and high performance liquid chromatography. The structure of prodrug was confirmed by analytical techniques, elemental analysis, fourier transform infrared spectroscopy, fourier transform nuclear magnetic resonance spectroscopy and mass spectroscopy. Preformulation studies revealed increased aqueous solubility with non significant change in lipophilicity of Nalidixic acid-Tryptophan conjugate than Nalidixic acid. In vitro reversion confirmed that the prodrug reversion was non significant in gastric environment, thus the objective of bypassing the GIT without any free drug release was achieved. However 67.83 % reversion of Nalidixic acid-Tryptophan conjugate to Nalidixic acid was observed in phosphate buffer pH 6.8 in presence of 20% w/v fresh rat fecal matter due to hydrolysis of amide linkage by amidase enzyme secreted by colonic microflora.