Comprehensive chemical characterization and biological evaluation of two Acacia species: A. nilotica and A. ataxacantha

The genus Acacia (Family Leguminosae) is composed of several medicinal plants used for treating miscellaneous diseases. Amid the important members of this genus, A. nilotica and A. ataxacantha are widely employed for their tremendous healing properties. Hence, this present work aimed to determine the total phenolic and flavonoid contents and investigate the antioxidant, antiproliferative, anti-enzyme and antimicrobial potentials of methanolic and water extracts of leaves and stem bark of A. nilotica and A. ataxacantha obtained by maceration and ultrasonication. The total phenolic and flavonoid contents were obtained in the range of 33.35–116.60 mg GAE/g and 0.26–49.90 mg RE/g, respectively, with the methanolic leaf extracts of both species showing the highest contents. Moreover, the methanolic extracts were observed to display higher antioxidant potentials in almost all antioxidant assays performed compared to the water extracts (ABTS: 52.66–943.81 mg TE/g, DPPH: 8.51–493.90 mg TE/g, CUPRAC: 106.39–1193.75 mg TE/g; FRAP: 31.38–416.21 mg TE/g, and phosphomolybdenum: 0.90–4.17 mM TE/g). However, the water extracts were seen to be better metal chelators than the methanolic extracts (8.47–36.85 mg EDTAE/g). Additionally, all extracts were found to exhibit anti-tyrosinase (30.79–74.80 mg KAE/g) and anti-amylase (0.10–1.10 mM ACAE/g) properties. With the exception of a few extracts, glucosidase and acetylcholinesterase inhibitions (1.69–2.12 mg ACAE/g and 0.42–2.61 mg GALAE/g, respectively) were also demonstrated. While the methanolic extracts of both species showed antimicrobial potency against all the 18 tested microorganisms (gram positive, gram negative, and fungi), the water extracts were effective only against the gram positive bacteria. The extracts were also found to exhibit antiproliferative effects on SH-SY5Y human neuroblastoma cells, with the methanolic extracts showing higher cytotoxic potential than the water extracts. Therefore, this study showed these species to be good sources of antioxidants, enzyme inhibitors, antimicrobials and antiproliferative agents, which could be of great interest for their applications as natural bioactive ingredients in the development of pharmaceuticals and nutraceuticals.