1. Division of Ethnopharmacology, Tropical Botanic Garden and Research Institute, Palode, Thiruvananthapuram 695562, Kerala, India, Department of Medicinal Chemistry, The Royal Danish School of Pharmacy, Universitetsparken 2, DK- 2100 Copenhagen, Denmark, Retrovirus Laboratory, Department of Virology, Statens Serum Institute, Artillerivej 5, DK-2300 Copenhagen S, Denmark, and Department of Chemistry, The Royal Veterinary and Agricultural University, Thorvaldsensvej 40, DK-1871, Frederiksberg, Denmark