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

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.