1. a Department of Pharmaceutical Chemistry , Faculty of Pharmacy , Rangsit University , Pathumtani 12000, Thailand
2. b Department of Pharmaceutical Botany , Faculty of Pharmaceutical Sciences , Chulalongkorn University , Bangkok 10330, Thailand
3. c Division of Pharmacognosy, Leiden/Amsterdam Center for Drug Research , Leiden University , Leiden 2300 RA, The Netherlands