Antibacterial and antioxidant activity of Juniperus thurifera L. leaf extracts growing in East of Algeria

Abstract

Aim: This work aimed to evaluate the biological activity of the leaf extracts of Juniperus thurifera L., which is an Algerian endemic tree that belongs to the family of Cupressaceae.

Materials and methods: The plant leaves were extracted in solvents of increasing polarity to obtain different extracts such as methanol, petroleum ether, chloroform, ethyl acetate, and aqueous extracts (MeE, PEE, ChlE, EtAE, and AqE). The antioxidant activity of four extracts (MeE, ChlE, EtAE, and AqE) was assessed by trapping test of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical. The evaluation of antibacterial activity of MeE, ChlE, EtAE, and PEE was done using the disk diffusion method on solid agar.

Results: The three extracts of EtAE, AqE, and MeE showed high antiradical activity toward the DPPH radical (IC₅₀=29.348 µg/mL, 37.538 µg/mL, and 52.573 µg/mL, respectively), while the lowest radical scavenging activity was expressed by the ChlE (IC₅₀=70.096 µg/mL). These extracts were active only toward the Gram-positive bacteria (Staphylococcus aureus ATCC and methicillin-resistant S. aureus) at different concentrations, and the highest activity was obtained with the ChlE with an inhibition diameter of 14 mm at the concentration of 1 g/mL. No inhibition was detected for all of these extracts against the Gram-negative tested strains (Escherichia coli ATCC, Pseudomonas aeruginosa ATCC, and Enterobacter cloacae (extended spectrum β-lactamase).

Conclusion: From this study, on the one hand, it was concluded that J. thurifera L. leaves extracts exhibited a very intense antioxidant potential toward the DPPH radical, and on the other hand, the antibacterial activity showed an action spectrum exclusively toward the Gram-positive bacteria.

Keywords: Juniperus thurifera L; antibacterial activity; antioxidant activity; extraction; trapping test of 1,1-diphenyl-2-picrylhydrazyl radical.

Figure-1

Reference antioxidant antiradical activity. Values are the mean ± SD (n=3).

Figure-2

Juniperus thurifera L. leaves extracts’ antiradical activity. Values are the mean ± SD (n=3). EBr=Methanolic extract; EChl=Chloroform extract; EEtA=Ethy acetate exctract; EAq=Aqueous extract

Figure-3

IC₅₀ of the antiradical activity of Juniperus thurifera leaf extracts and reference antioxidants toward 1,1-diphenyl-2-picrylhydrazyl radical. Values represent mean ± SD (n=3). Values are compared to the BHT. Ns=Not significant, ***p<0.001. EBr=Methanolic extract, EChl=Chloroform extract; EEtA=Ethy acetate exctract; EAq=Aqueous extract

Figure-4

Antibacterial activity of Juniperus thurifera L. crude extract.

Figure-5

Antibacterial activity of Juniperus thurifera L. chloroform extract.

Figure-6

Antibacterial activity of Juniperus thurifera L. petroleum ether extract.

Figure-7

Antibacterial activity of Juniperus thurifera L. ethyl acetate extract.