Identification and characterization of anthocyanins and non-anthocyanin phenolics from Australian native fruits and their antioxidant, antidiabetic, and anti-Alzheimer potential

Polyphenols are vital bioactive constituents that have beneficial effects on human health. The aim of this study was to characterize the biologically active phenolic metabolites in Australian native commercial fruits (Kakadu plum, Davidson’s plum, quandong peach, and muntries) and their antioxidant, α-glucosidase, and acetylcholinesterase inhibition activities. Polyphenols were measured through total phenolic content (TPC), total flavonoid content (TFC), total condensed tannin (TCT), and total monomeric anthocyanin content (TMAC). Moreover, different in-vitro biological assays (DPPH, ABTS, FICA, OH-RSA, α-glucosidase, and acetylcholinesterase inhibition activities) were conducted to measure the antioxidant, anti-diabetic, and anti-Alzheimer’s potential of these selected fruits. LC-ESI-QTOF-MS/MS was implied for identification and quantification purposes. In this study, a total of 307 bioactive metabolites (51 phenolic acids, 194 flavonoids, 15 tannins, 23 other polyphenols, 5 stilbenes, 12 lignans, and 7 terpenoids) were putatively identified. A total of 41 phenolic compounds were quantified/semi-quantified. Kakadu plum was identified with a higher concentration of polyphenols and biological activities compared to Davidson plum, quandong peach, and muntries. Molecular docking was also conducted to discover the actual role of the most abundant phenolic metabolites in the α-glucosidase and acetylcholinesterase inhibition activities.