1. College of Pharmacy, Pusan National University, Busan 609-735, Korea, Shenyang Pharmaceutical University, Shenyang 110016, People's Republic of China, College of Pharmacy, Kyung Hee University, Seoul 130-701, Korea, Korea Research Institute of Chemical Technology, Daejon 305-343, Korea, and Department of Biology, Hannam University, Daejon 306-791, Korea