1. 1Department of Chemistry, Faculty of Sciences, Chiang Mai University, Chiang Mai, 50200, Thailand; fax: 66 53 892277
2. 2Department of Chemistry, Faculty of Sciences, Chiang Mai University, Chiang Mai, 50200, Thailand; fax: 66 53 892277; 2 Division of Clinical Immunology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, 50200, Thailand; fax: 66 53 9460
3. 3Division of Clinical Immunology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, 50200, Thailand; fax: 66 53 9460