Synthesis of some pyrazolone derivatives from ciprofloxacin and study of their cytotoxicity

Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic used in the treatment of a wide range of mild to moderate Gram-positive and Gram-negative infections. As ciprofloxacin, has a keto and a carboxylic acid group in the ortho position, an extra pyrazole ring system on the ciprofloxacin molecule can be created. Pyrazolone and its derivatives are used for their analgesic (Gursoy et al., 2000), anti-inflammatory (Satyanarayana and Rao, 1995), antipyretic (Manna et al., 1992), antiarrhythmic, antifungal (Bekhit and Fahmy, 2003), muscle relaxing, psychoanaleptic, anticonvulsant, enzyme inhibiting (Regan et al., 2003), antidiabetic and antibacterial activities. So, the chemistry of pyrazolone and its derivatives is particularly interesting because of their potential application in medicinal chemistry. In continuation of our work to investigate the cytotxicity (Islam et al., 2001) of pyrazolone derivatives, three pyrazolone derivatives from ciprofloxacin have been synthesized and we report herein the result of cytotoxicity.


Introduction
Ciprofloxacin is a broad-spectrum fluoroquinolone antibiotic used in the treatment of a wide range of mild to moderate Gram-positive and Gram-negative infections. As ciprofloxacin, has a keto and a carboxylic acid group in the ortho position, an extra pyrazole ring system on the ciprofloxacin molecule can be created. Pyrazolone and its derivatives are used for their analgesic (Gursoy et al., 2000), anti-inflammatory (Satyanarayana and Rao, 1995), antipyretic (Manna et al., 1992), antiarrhythmic, antifungal (Bekhit and Fahmy, 2003), muscle relaxing, psychoanaleptic, anticonvulsant, enzyme inhibiting (Regan et al., 2003), antidiabetic and antibacterial activities. So, the chemistry of pyrazolone and its derivatives is particularly interesting because of their potential application in medicinal chemistry. In continuation of our work to investigate the cytotxicity (Islam et al., 2001) of pyrazolone derivatives, three pyrazolone derivatives from ciprofloxacin have been synthesized and we report herein the result of cytotoxicity.

Materials and Methods
All melting points were recorded by thin disk method on a "Fischer Johns" electro thermal melting point apparatus. Infrared spectra were recorded on DR-8001, Shimadzu FTIR spectrophotometer as a solid, which was finely grounded in a small agate mortar with a drop of nujol (liquid hydrocarbon) as a mull and also in KBr disk. 1 H-NMR spectra were measured by WP 400-NMR spectrometer, deuterated solvents such as dimethylsulfoxide (DMSO-d6) were used as solvents and the chemical shifts were quoted as 8-value relative to tetramethyl silane (TMS, 8=O) as an internal standard. The purity of compounds was checked by TLC on silica gel plates and iodine was used as a visualizing agent.

Received
Hatching and maintenance of brine shrimp (Islam and Mohsin, 2007;Solis et al, 1993): Brine shrimps (Artemia salina) were used as test animal for the investigation of cytotoxicity. The essential condition for brine shrimp (temperature 27-30°C, salinity 30-35 ppt, pH 7.5-8.5, and strong aeration) was established by mixing sodium chloride salts in water. Natural or artificial light (at night) was required and constant oxygen supply was carried out by bubble pump machine. After obtaining the desired condition, about one teaspoon of brine shrimp eggs was added to the beaker. After 12 hours hatching aggregated brine shrimp nauplii were collected in another beaker and rinse with fresh water and applied for testing. Counting of nauplii: After 1, 2, 3 and 4 hours, the test tubes were observed and the number of survived nauplii in each test tube was counted and results were noted. The percentage of mortality of brine shrimp was calculated for each sample that gives different mortality for different concentrations. An approximate linear correlation was observed when logarithm of concentration was plotted against percentage of mortality and the values of IC50 were calculated for each sample. The IC50 represents the concentration of a compound, which will kill, or inactive 50 percent of the test animal. IC50 is inversely proportional to the toxicity of a compound, i.e. the lower the IC50 the higher the toxicity.

Results
Physical constants give the preliminary idea about the formation of new compounds (

Discussion
In the present work, the synthesized compounds were investigated for their property as biologically active agents by brine shrimp lethality bioassay. Among them the compounds 1b are very highly active. 1a and 1c are highly active but ciprofloxacin is moderately active.
The chemical structure of a drug is important as the relatively minor modification in the drug molecule may results a major change in pharmacological properties.