Identification of Phytochemicals in Bioactive Extracts of Acacia saligna Growing in Australia

Acacia saligna growing in Australia has not been fully investigated for its bioactive phytochemicals. Sequential polarity-based extraction was employed to provide four different extracts from individual parts of A. saligna. Bioactive extracts were determined using in vitro antioxidant and yeast α-glucosidase inhibitory assays. Methanolic extracts from barks, leaves, and flowers are the most active and have no toxicity against 3T3-L1 adipocytes. Compound isolation of bioactive extracts provided us with ten compounds. Among them are two novel natural products; naringenin-7-O-α-L-arabinopyranoside 2 and (3S*,5S*)-3-hydroxy-5-(2-aminoethyl) dihydrofuran-2(3H)-one 9. D-(+)-pinitol 5a (from barks and flowers), (−)-pinitol 5b (exclusively from leaf), and 2,4-di-t-butylphenol 7 are known natural products and new to A. saligna. (−)-Epicatechin 6, quercitrin 4, and myricitrin 8 showed potent antioxidant activities consistently in DPPH and ABTS assays. (−)-Epicatechin 6 (IC(50) = 63.58 μM), D-(+)-pinitol 5a (IC(50) = 74.69 μM), and naringenin 1 (IC(50) = 89.71 μM) are the strong inhibitors against the α-glucosidase enzyme. The presence of these compounds supports the activities exerted in our methanolic extracts. The presence of 2,4-di-t-butylphenol 7 may support the reported allelopathic and antifungal activities. The outcome of this study indicates the potential of Australian A. saligna as a rich source of bioactive compounds for drug discovery targeting type 2 diabetes.