1. Department of Chemistry, College of Natural Sciences, Seoul National University , Seoul 08826, Korea
2. School of Pharmacy, Chung-Ang University , Seoul 06974, Korea
3. Department of Life Science, Chung-Ang University , Seoul 06974, Korea
4. Key Laboratory of Natural Medicines of the Changbai Mountain, Ministry of Education, College of Pharmacy, Yanbian University , Yanji 133002, Jilin Province, China