H OH metabolites OH Article Untargeted and Targeted Metabolomic Profiling of Australian Indigenous Fruits Vuanghao Lim 1,2,* , Sara Ghorbani Gorji 1, Venea Dara Daygon 1 and Melissa Fitzgerald 1,* 1 School of Agriculture and Food Sciences, The University of Queensland, Brisbane, QLD 4072, Australia;
[email protected] (S.G.G.);
[email protected] (V.D.D.) 2 Integrative Medicine Cluster, Advanced Medical and Dental Institute, Universiti Sains Malaysia, Bertam, Kepala Batas 13200, Penang, Malaysia * Correspondence:
[email protected] (V.L.); m.fi
[email protected] (M.F.) Received: 18 February 2020; Accepted: 11 March 2020; Published: 19 March 2020 Abstract: Selected Australian native fruits such as Davidson’s plum, finger lime and native pepperberry have been reported to demonstrate potent antioxidant activity. However, comprehensive metabolite profiling of these fruits is limited, therefore the compounds responsible are unknown, and further, the compounds of nutritional value in these native fruits are yet to be described. In this study, untargeted and targeted metabolomics were conducted using the three fruits, together with assays to determine their antioxidant activities. The results demonstrate that targeted free and hydrolysed protein amino acids exhibited high amounts of essential amino acids. Similarly, important minerals like potassium were detected in the fruit samples. In antioxidant activity, Davidson’s plum reported the highest activity in ferric reducing power (FRAP), finger lime in antioxidant capacity (ABTS), and native pepperberry in free radical scavenging (DPPH) and phosphomolybdenum assay. The compounds responsible for the antioxidant activity were tentatively identified using untargeted GC GC-TOFMS and × UHPLC-QqQ-TOF-MS/MS metabolomics.