1. College of Pharmacy, Chosun University, 375 Seosuk-dong, Dong-gu, Gwangju 501-759, Republic of Korea, National Institute of Medicinal Materials, 3B Quang Trung, Hoan Kiem, Hanoi, Vietnam, Institute of Chemistry, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Caugiay, Hanoi, Vietnam, and College of Pharmacy, Chonnam National University, Yongbong-dong, Gwangju 500-757, Republic of Korea