Antibacterial and Antiproliferative Activities of Azadirachta indica Leaf Extract and Its Effect on Oil-in-Water Food Emulsion Stability

Abstract

The present study aims to identify and quantify the phenolic compounds of Azadirachta indica leaf extract using HPLC-MS and to evaluate the antioxidant, antibacterial (against different Gram-positive and negative bacteria) and in vitro anti-proliferative activities of this extract (against breast, human liver and cervix adenocarcinoma-derived cells). The application of this extract as a natural antioxidant for food preservation was also tested on oil-in-water food emulsions for the first time in the present work in order to determine the use of Azadirachta indica leaves as a natural additive to preserve the food against lipid oxidation and rancidity. The results obtained revealed that 50%-aqueous ethanol leaf extract showed the best extraction yield (25.14%), which was characterized by a high content in phenolic compounds and strong antioxidant activity. Moreover, this leaf extract inhibited the growth of the bacterial strains tested (Staphylococcus aureus, Escherichia coli, Salmonella paratyphi and Micrococcus luteus) and showed better anti-proliferative activity against breast and cervix adenocarcinoma-derived cells than human liver cancer cells after 48 h of treatment. Additionally, Azadirachta indica leaf extract showed almost similar effects as gallic acid solutions (0.25% and 0.5%) in preserving the oxidation of oil-in-water food emulsions and prevented the formation of secondary oxidation products (malondialdehyde) as well. The results obtained suggested that extracts of Azadirachta indica leaves are a potential source of antioxidant and antibacterial compounds and pointed to the potential of these natural extracts as therapeutic agents.

Keywords: Azadirachta indica; HPLC-MS; anti-bacterial; antioxidant; cancer cells; food emulsion.

Figure 1

Peroxide value (PV) of emulsions incorporated with A. indica leaf 50%-aqueous EtOH extract (0.25% and 0.5%, v/v) during storage. Error bars represent the standard deviation (n = 3). Lowercase letters indicate significant differences between emulsion samples on the same day at α = 0.05, and uppercase letters indicate significant differences between the days of storage for the same sample at α = 0.05.

Figure 2

pH changes of the emulsions treated with A. indica leaf 50%-aqueous EtOH extract (0.25% and 0.5%, v/v) during storage. Error bars represent the standard deviation (n = 3). Lowercase letters indicate significant differences between emulsion samples on the same day at α = 0.05, and uppercase letters indicate significant differences between days of storage for the same emulsion sample α = 0.05.

Figure 3

TBARS value of the emulsions incorporated with A. indica leaf 50%-aqueous EtOH extract (0.25% and 0.5%, v/v) during storage. Error bars represent the standard deviation (n = 3). Lowercase letters indicate significant differences between emulsion samples on the same day at α = 0.05, and uppercase letters indicate significant differences between days of storage for the same emulsion sample at α = 0.05.

Figure 4

Effect of A. indica leaf 50%-aqueous EtOH extract (AI; 2% and 7%, v/v) on cell viability assayed 48 h after treatment. CTR, non-treated cells, PBS and control cells incubated in the presence of solvent without AI. Error bars represent the standard deviation (n = 3). Lowercase letters indicate significant differences between the three cancer cell lines with the same treatment at α = 0.05, and uppercase letters indicate significant differences between the same cancer cell line with different treatments at α = 0.05.