1. National Agriculture Research Center, Ministry of Agriculture, Forestry and Fisheries, 3-1-1 Kannondai, Tsukuba 305, Japan
2. National Food Research Institute, Ministry of Agriculture, Forestry and Fisheries, 2-1-2, Kannondai, Tsukuba 305, Japan
3. Department of Chemistry, School of Science, Kwansei-Gakuin University, Uegahara, Nishinomiya 662, Japan