1. Natural Products Research Laboratories, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599-7568, United States
2. Division of Medicinal Chemistry & Natural Products, Eshelman School of Pharmacy, University of North Carolina, Chapel Hill, North Carolina 27599-7568, United States
3. Chinese Medicine Research and Development Center, China Medical University and Hospital, Taichung, Taiwan