1. Department of Chemistry, University of Otago, P. O. Box 56, Dunedin 9054, New Zealand
2. The New Zealand Institute for Plant and Food Research Limited, Private Bag, Palmerston North 11600, New Zealand
3. The New Zealand Institute for Plant and Food Research Limited, Department of Chemistry, University of Otago, P.O. Box 56, Dunedin 9054, New Zealand