Two Validated Spectrofluorometric Methods for Determination of Gemifloxacin Mesylate in Tablets and Human Plasma

Two new, sensitive, and selective spectrofluorometric methods were developed for the determination of gemifloxacin mesylate (GFX) in tablets and spiked human plasma. Method A was based on measurement of the enhanced fluorescence spectral behaviour of GFX in a sodium dodecyl sulphate (SDS) micellar system. In aqueous solution of acetate buffer pH 5.5, the fluorescence intensity of GFX was greatly enhanced about tenfold in the presence of SDS. The fluorescence intensity was measured at 402？nm after excitation at 274？nm. Method B was based on Hantzsch condensation reaction between the primary amino group of GFX with acetylacetone and formaldehyde in acetate buffer of pH 3.5 yielding a highly yellow fluorescent derivative. The reaction of GFX with acetylacetone-formaldehyde system solution resulted in bathochromic shift of both emission (476？nm) and excitation (420？nm) wavelengths. The fluorescence intensity was directly proportional to the concentration over the range 10–1000？ng/ml and 100–2000？ng/ml for method A and B, respectively. The proposed methods were applied successfully for determination of GFX in its tablets and spiked plasma. Therefore, these methods can be considered of real interest for reliable and practical quality control analysis of GFX. 1. Introduction Gemifloxacin mesylate (GFX) is a fluoronaphthyridone with a novel oxime functionalised pyrrolidine (Figure 1) [1]. It possesses a dual mechanism of action by inhibiting the bacterial topoisomerase IV and gyrase enzymes, resulting in interruption of bacterial DNA synthesis. Therefore, it has broad-spectrum activity against Gram-positive and Gram-negative organisms comparable to those of its quinolone counterparts which have the same pyrrolidine side chain [1, 2]. GFX was first approved by the FDA for clinical use in 2003 for the treatment of community acquired pneumonia and acute bacterial exacerbation of chronic bronchitis [3]. Figure 1: Chemical structure of gemifloxacin mesylate. Several analytical methods were reported for determination of gemifloxacin in pharmaceutical preparations or human plasma by visible spectrophotometry [4, 5], capillary electrophoresis [6], HPLC-MS-MS [7], HPLC [8], and HPTLC [9]. However, these methods showed some drawbacks such as being time-consuming, tedious, or requiring expensive instruments that limit their use in quality control and routine clinical studies in developing countries where the cost is a main concern. Spectrofluorimetric analysis constitutes a widespread, effective technique to improve analysis selectivity and sensitivity. Although, limited