1. 1Department of Chemistry, University of Jordan, Amman 11942, Jordan
2. 2Medical Biochemistry Research Unit, Medicinal and Aromatic Plants Research Institute, National Center for Research, P.O. Box: 2404, Khartoum, Sudan
3. 3H.E.J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi-75270, Pakistan