Phytochemical divergence in 45 accessions of Terminalia ferdinandiana (Kakadu plum)

• Hydrolysable tannins and ellagic acid are the major phenolic compounds of Kakadu plum.
• Kakadu plum appears as exceptionally rich source of ellagic acid among edible fruits.
• Fruits from the Northern Territory contain higher levels of phenolic compounds.
• Fruits from the Western Australia contain higher levels of sugars.
• The highest vitamin C level (32% DW) had accession 15 from the Northern Territory.

This study investigated the variations in the levels of phenolic compounds, vitamin C, sugars and antioxidant capacities of 45 newly collected accessions of Terminalia ferdinandiana (Kakadu plum), a native Australian fruit utilised in dietary supplement industry. Pattern recognition tools, principal component analysis (PCA) and agglomerative hierarchical clustering (AHC) were applied to understand interrelationships between the antioxidant capacities [Ferric reducing antioxidant power (FRAP) and Oxygen radical absorbance capacity (ORAC)] and antioxidant groups: phenolic compounds and vitamin C. On the basis of these parameters AHC classified samples into three main groups, with accessions 2, 8, 15, 6, 3 and 5 from the Northern Territory, Australia, representing superior quality fruits combining high levels of total phenolics (505.2 to 376.1 mg GA E/g DW), vitamin C (322.2 to 173.5 mg/g DW), with pronounced antioxidant capacities (FRAP: 5030.5 to 4244.9 μmol Fe2+/g DW; ORAC: 3861.5 to 2985.6 μmol Trolox E/g DW). Hydrolysable tannins and ellagic acid were identified as the major phenolic compounds. The levels of ellagic acid varied from 140.2 to 30.5 mg/g DW, which places Kakadu plum as a unique edible source of this compound. The levels of sugars varied from 619.0 to 130.0 mg Glu E/g DW. This study for the first time revealed a unique phytochemical profile and significant variability in phytochemical composition of Kakadu plum. These features create opportunities for selection of sources with different characteristics addressing the needs of the nutraceutical industry, food processors and the consumers of fresh fruit.