Preparation and characterization of Trimethoprim inclusion complex with Methyl-ÃÂ²-Cyclodextrin and determination of its antimicrobial activity

Ana Figueiras Olga Cardoso

doi:10.4172/2153-2435.1000405

Abstract

The present study focuses on the formation and characterization of inclusion complexes between Trimethoprim (TMP), an inhibitor of bacterial dihydrofolate reductase, and cyclodextrins, namely, methyl-βeta-cyclodextrin (MBCD) and hydroxylpropyl-βeta-cyclodextrin (HBCD) in aqueous solution. MBCD was selected to prepare inclusion complexes in the solid state. These complexes were prepared by different methods: spray drying, kneading and freeze drying. Physical mixtures were prepared as reference. The prepared systems were then characterized by different techniques: Differential scanning calorimetry (DSC), Fourier Transform Infrared Spectroscopy (FT-IR) and Scanning Electron Microscopy (SEM). The dissolution profile and the antimicrobial activity of Trimethoprim and the inclusion complexes were evaluated using the dissolution test, and the disk diffusion methodology, respectively. An increase of TMP solubility was observed in phase solubility studies. The obtained apparent stability constants (Ks) showed that MBCD formed an inclusion complex more stable with the drug than HPBCD, so it was decided to prepare inclusion complexes in solid state with MBCD. The results obtained with DSC, FTIR and SEM proved the formation of inclusion complexes in solid state. The dissolution profile and the antibacterial activity increased with the complexation process.

Highlights

After 75 minutes a high percentage of dissolution it is observed, especially for the Freeze-dried binary system (FD) system, which showed 99% of dissolved drug. These results suggest that complexation with MBCD can increase the efficacy of dissolution of TMP
The results of the phase solubility studies reveal that the solubility of TMP increases in the presence of MBCD and HPBCD
The calculated apparent stability constants allowed concluding that TMP forms more stable inclusion complexes with MBCD than those formed with HPBCD

Summary

Introduction

TMP (5-(3,4,5-trimethoxybenzyl)-pyrimidine-2,4-diamine),(Figure 1) is a synthetic antibiotic, which inhibits bacterial dihydrofolate reductase, the enzyme that reduces the dihydrofolate to tetrahydrofolate together with the cofactor nicotinamide adenine dinucleotide phosphate (NADPH), inhibiting the synthesis of nitrogenous bases necessary for the replication of bacterial nucleic acids [1].This drug is used in the treatment of uncomplicated urinary tract infections caused by aerobic Gram-positive cocci (Streptococcus pneumoniae, Staphylococcus aureus) and coagulase-negative species, including Staphylococcus saprophyticus and shows activity towards Gram-negative organisms (Enterobacter spp., Escherichia coli, Haemophilus influenzae, Salmonella spp., Proteus mirabilis, Serratia spp., Providencia spp., Klebsiella spp., Proteus mirabilis, Shigella spp., Morganella morganii) [1].According to the Biopharmaceutical Classification System (BCS), TMP is classified as a class II drug showing low solubility and high permeability due to its lipophilicity, which reduces its bioavailability [2].A strategy used to increase the solubility, and bioavailability of poorly water soluble compounds such as TMP is the formation of inclusion complexes with cyclodextrins (CDs) [3].CDs are oligosaccharides which are formed by D-(+) glucopyranose units linked with alpha-1,4-glycosidic bonds and are obtained by enzymatic degradation of the starch by action of the enzyme cyclodextrin glycosyl transferase (CGTase) [4]. (Figure 1) is a synthetic antibiotic, which inhibits bacterial dihydrofolate reductase, the enzyme that reduces the dihydrofolate to tetrahydrofolate together with the cofactor nicotinamide adenine dinucleotide phosphate (NADPH), inhibiting the synthesis of nitrogenous bases necessary for the replication of bacterial nucleic acids [1] This drug is used in the treatment of uncomplicated urinary tract infections caused by aerobic Gram-positive cocci (Streptococcus pneumoniae, Staphylococcus aureus) and coagulase-negative species, including Staphylococcus saprophyticus and shows activity towards Gram-negative organisms (Enterobacter spp., Escherichia coli, Haemophilus influenzae, Salmonella spp., Proteus mirabilis, Serratia spp., Providencia spp., Klebsiella spp., Proteus mirabilis, Shigella spp., Morganella morganii) [1]. The natural cyclodextrins obtained with higher yield by the action of the CGTase are α-cyclodextrin, β-cyclodextrin and γ-cyclodextrin that contain six, seven and eight glucose units, respectively Due their physicochemical properties, their structure with an hydrophilic internal cavity and an hydrophobic exterior, they can be used as host for a variety of guest molecules to form inclusion complexes by non-covalent bonds

Methods

Results

Conclusion