1. Division of Marine Environment and Bioscience, College of Ocean Science and Technology, Korea Maritime University, #1 Dongsam, Youngdo, Busan 606-791, Korea, Natural Products Research Institute, College of Pharmacy, Seoul National University, #28 Yungun, Jongro, Seoul 110-460, Korea, and School of Agricultural Biotechnology, Seoul National University, San 56-1, Sillim, Gwanak, Seoul 151-921, Korea