1. Faculty of Science, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada
2. Sciences Biologiques, Université de Pau, Pau, France
3. Faculty of Pharmacy, Chiang Mai University, Chiang Mai, Thailand
4. Universidad National, Heredia, apdo 86—3000, Costa Rica
5. Department of Plant Science, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada