1. Natural Products Research Institute, College of Pharmacy, Seoul National University, San 56-1, Sillim, Gwanak, Seoul 151-742, Korea
2. College of Pharmacy, Seoul National University, San 56-1, Sillim,
Gwanak, Seoul 151-742, Korea
3. Department of Agricultural Biotechnology, College of Agriculture & Life Science, Seoul National University, San 56-1, Sillim, Gwanak, Seoul 151-921, Korea