Screening of phytochemicals and in vitro evaluation of antibacterial and antioxidant activities of leaves, pods and bark extracts of Acacia nilotica (L.) Del.

• Comparative phytochemical analysis of A. nilotica extracts by LCMS, HPLC/DAD and FTIR.
• Total phenolic, flavonoid and protein contents of leaves pods and bark extracts were investigated.
• Antioxidant activities of extracts showed direct relationship with total phenolic content.
• Leaves showed high contents of phenolics, proteins, antibacterial and antioxidant activities comparatively.

The objective of this study was to determine the phytochemical content, antibacterial activity and antioxidant activity of leaves, bark and pods of Acacia nilotica. The different extracts of acacia were evaluated for total phenolic, flavonoid and protein contents, antibacterial (agar well diffusion and broth dilution methods) and antioxidant (DPPH; 1,1-diphenyl-2-picrylhydrazyl assay) activities. The characterization and identification of phenolic compounds was carried out by Liquid Chromatography–tandem Mass Spectrometry analysis. The MS2 fragmentation pattern showed the presence of galloylated catechins and gallocatechin derivatives in tested extracts. The results indicated that all parts of the plant, but especially leaves, were effective in inhibiting the growth of antibiotic resistant strains of Escherichia coli and Salmonella species obtained from clinical and food isolates. The leaves were found to be rich in total phenolic content, proteins and high antioxidant activity as compared to pods and bark. The presence of functional groups of active compounds was confirmed by Fourier transform infrared spectroscopy (FTIR) analysis of plant extracts. It was concluded that all tested parts of A. nilotica had antibacterial and antioxidant activities. These properties might be due to the presence of high total phenolic content, proteins and/or flavonoids. Hence the extracts of leaves, bark and pods of A. nilotica represent a potential source of antibacterial and antioxidant compounds that may be used in food, agriculture and/or pharmaceutical products.