Biosynthesis, characterization, and antibacterial activity of ZnO nanoaggregates using aqueous extract from Anacardium occidentale leaf: comparative study of different precursors
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Date
2021
Journal Title
Journal ISSN
Volume Title
Publisher
Beni-Suef University Journal of Basic and Applied Sciences
Abstract
Background: Various parts of Anacardium occidentale plant possess curative qualities like antidiabetic, anti inflammatory, antibacterial, antifungal, and antioxidant. Aqueous extract of this plant leaf was used in
biosynthesizing zinc oxide (ZnO) nanoaggregates using two precursors of zinc salt (zinc acetate dihydrate
[Zn(CH3COO)2∙2H2O] and zinc chloride [ZnCl2]). The synthesized ZnO samples were used in a comparative study to
investigate the antibacterial activity against selected Gram-positive and Gram-negative microbes [Staphylococcus
aureus, Exiguobacterium aquaticum (Gram +ve) and Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii
(Gram −ve)]. The synthesized ZnO nanoaggregates from the two precursors were characterized using Fourier
transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy
(TEM), and energy-dispersive x-ray spectroscopy (EDX) techniques.
Results: Micrographs of SEM and TEM confirmed nanoparticles agglomerated into aggregates. While spherical
nanoaggregates were identified in samples prepared from Zn(CH3COO)2∙2H2O, flake-like structures were identified
in samples synthesized from ZnCl2. Particle size determined by TEM was 107.03 ± 1.54 nm and 206.58 ± 1.86 nm for
zinc acetate dihydrate and zinc chloride precursors respectively. ZnO nanoaggregate synthesized using zinc acetate
as precursor gave higher antibacterial activity than its counterpart, zinc chloride with K. pneumonia recording the
highest inhibition zone of 2.08 ± 0.03 mm (67.53%) whereas S. aureus recorded the least inhibition zone of 1.06 ±
0.14 mm (34.75%) for ZnO nanoaggregate from zinc chloride precursor. Also, antibacterial activity increases with
increasing concentration of the extract in general. However, A. baumannii, E. aquaticum, and K. pneumoniae did not
follow the continuity trend with regards to the 250 ppm and 500 ppm concentrations.
Conclusion: Biosynthesis of ZnO nanoaggregates using aqueous extract of A. occidentale leaf from zinc acetate
dihydrate and zinc chloride as precursors was successful with the formation of nanospheres and nanoflakes. The
study suggested that A. occidentale sp. could be an alternative source for the production of ZnO nanoparticles and
are efficient antibacterial compounds against both Gram +ve and Gram −ve microbes with its promising effect
against infectious bacteria
Description
Research Article
Keywords
Zinc oxide nanoaggregate, Zinc acetate dihydrate, Zinc chloride, Anacardium occidentale, Antibacterial activity, Biosynthesis