1. HortResearch Ltd., Ruakura Research Centre, Private Bag 3123, Hamilton, New Zealand; Natural Products Processing Division, Industrial Research Ltd., Gracefield Road, P.O. Box 31310, Lower Hutt, New Zealand; AgResearch Ltd., Ruakura Research Centre, Private Bag 3123, Hamilton 3240, New Zealand; Chemistry Department, The University of Waikato, Private Bag 3105, Hamilton, New Zealand; and National Veterinary Institute, P.B. 8156 Dep., NO-0033 Oslo, Norway