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Objective: The aim of the present study was to prepare the amino acid prodrugs of bromhexine hydrochloride to improve its solubility.

Methods: All the prodrugs were synthesized by first reacting bromhexine with tert-butoxycarbonyl (Boc) protected amino acid and then deprotection was carried out by using trifluoroacetic acid. These prodrugs were characterized by their melting points, NMR, mass and FTIR spectroscopy. Solubility and partition coefficient of bromhexine and various prodrugs were determined. The solution stability of various prodrugs was also determined in various buffers of pH ranging from 2 to 10. Degradation rate constants and half-life were also determined at various pH.

Results and discussion: The structures of all the synthesized prodrugs were confirmed by NMR, mass and FTIR spectra. The prodrug 2-N-l-alanyl-bromhexine hydrochloride showed maximum solubility and minimum partition …