1. Central Department of Chemistry, Tribhuvan University, Kirtipur, Kathmandu 44618, Nepal
2. Graduate School of Pharmaceutical Sciences, Kumamoto University, 5-1 Oe-honmachi, Chuo-Ku, Kumamoto 862-0973, Japan
3. Program for Leading Graduate Schools, HIGO Program, Kumamoto University, 5-1 Oe-honmachi, Chuo-Ku, Kumamoto 862-0973, Japan