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(3 H )-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.