Undaria pinnatifida (U.pinnatifida) is a type of brown seaweed native to the temperate shores of Japan, Korea and China. It was introduced to New Zealand accidently through ships travelling from Asia in 1987. Since then, it has widely spread to areas frequented by vessels in New Zealand. This study was carried out to investigate the fucoxanthin content and antioxidant properties of U.pinnatifida collected from the Marlborough Sounds, New Zealand.

U.pinnatifida was collected from two locations - Port Underwood and Pelorus Sound of the Marlborough Sounds, from their appearance in late autumn (June) to the onset of senescence in early summer (November), 2011. Results showed that freeze dried U.pinnatifida harvested from Port Underwood had higher fucoxanthin content in the blade particularly in July, August and September compared to Pelorus Sound. The sporophyll which is usually discarded when processing U.pinnatifida as a dried food product was also found to contain a significant amount of fucoxanthin, but all lower than that in the blade, throughout the harvest season. New Zealand U.pinnatifida was further processed in this study to produce cut wakame, which was the most popular form of commercially dried products available in New Zealand. The New Zealand processed U.pinnatifida was compared to four other commercial dried products from Korea (Ottogi and Chung Jung Won) and Japan (Wako Shokai and Riken) in terms of their fucoxanthin content and antioxidant activities. For antioxidant measurement, 1,1- diphenyl-2-picrylhydrazyl assay (DPPH) and cupric reducing antioxidant capacity (CUPRAC) were utilised. Processed U.pinnatifida had lower fucoxanthin content and antioxidant capacities compared to the freeze-dried U.pinnatifida. Fucoxanthin content and antioxidant activity of New Zealand processed U.pinnatifida was not significantly different from other commercial samples. In conclusion, sporophyll is a useful resource for fucoxanthin extraction, and New Zealand U.pinnatifida is a valuable food or nutraceuticals resource, as it has similar fucoxanthin content and antioxidant activity compared with Japanese and Korean U.pinnatifida products.