1. Department of Chemistry, Quaid-i-Azam University, Islamabad, Pakistan
2. Institute of Organic Chemistry, University of Hannover, Schneiderberg 1B, D-30167 Hannover, Germany
3. Institute of Clinical Biochemistry, Hannover Medical School, D-30643 Hannover, Germany
4. Institute of Pharmacology, Technical University of Braunschweig, D-38106 Braunschweig, Germany