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Drug Discovery
Fluorescence has played a pivotal role in Drug Discovery & Study of some of the widely used antibiotics in treatment of Critical illnesses. [16] Photophysical properties of two widely used antibiotic fluoroquinolone drugs, namely Norfloxcacin (NOR) and ofloxacin (OFL) have been investigated in biomimicking environments formed by bile salts. Experimental results demonstrate that photophysical enhancement and fall of a particular prototropic species are sensitive to the excitation wavelength in bile salt aggregates. Excitation at shorter wavelengths reveals quenching of fluorescence of these fluroquinolones with addition of NaDC, NaTC and NaGDC. On the contrary, a steady increase in the fluorescence intensity with a continuous red shift upon excitation at longer wavelength is Observed. The experimental results were rationalized in terms of the fact that neutral and zwitterionic species of fluoroquinolone molecules in bile salt aggregates are selectively excited at shorter wavelength while the cationic form of fluoroquinolone molecules are excited at longer wavelength. The excess hydronium ions in the hydrophilic surface of bile salt aggregates convert the neutral species of NOR and OFL into a cationic species causing an enhancement in the emission intensity.Its found that NaGDC and NaTC because of the conjugate head group are more effective in converting the neutral species of fluoroquinolones into a cationic species than NaDC. The quenching order is in accordance with hydrophobicity indices of bile salt.