1. Pharmacia & Upjohn, Pharmaceutical Development, Rapid Structure Characterization Group, Kalamazoo, Michigan 49001-0199, Department of Pharmacognosy and Natural Products Chemistry, Faculty of Pharmacy, Al-Azhar University, Nasr City, Cairo, Egypt, Department of Pharmaceutical Sciences, School of Pharmacy, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, and Centre for Scientific Research into Plant Medicine, Mampong-Akwapim, Ghana