Nutritional properties of commercially grown native Australian fruits: Lipophilic antioxidants and minerals

A high level of antioxidant activity of lipophilic fractions obtained from commercially grown native Australian fruits, as evaluated in the oxygen radical absorbance capacity assay for lipophilic antioxidants (ORAC-L), was identified for the first time. The level of contribution of lipophilic fractions varied from 5.8% (quandong) to 30.7% (riberry) of the total oxygen radical scavenging capacity (ORAC-T). Vitamin E components - α-tocopherol, γ-tocopherol and δ-tocopherol and lutein - were identified as the main sources of this activity. Among the evaluated sources, Kakadu plum emerges as a fruit with unique nutritional qualities: it exhibited a superior ORAC-T value (430.0 μM trolox eq/g fresh weight, TEq/g FW) with 26.7% contribution of the lipophilic fraction. The major compounds of Kakadu plum's lipophilic fraction were α-tocopherol (1.022 ± 0.1 mg/100 g, FW), lutein (0.26 ± 0.01 mg/100 g FW) and chlorophyll a and b (2.72 ± 0.1 and 0.54 ± 0.1 mg/100 g FW, respectively). With regards to mineral content, the levels of major minerals, such as potassium, phosphorus, calcium, magnesium, and trace elements such as iron, zinc, manganese, selenium and copper as well as cobalt, nickel, aluminium and led in native Australian fruits are similar to the levels of these elements in a range of vegetables and frutis produced and consumed elsewhere.