1. Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom, Pharmacognosy Research Laboratories, Department of Pharmacy, King's College, London, 150 Stamford Street, London SE1 8WA, United Kingdom, and National Pharmaceutical Control Bureau, Jalan University, 46730, Petaling Jaya, Malaysia