Biogenic synthesis of copper oxide nanoparticles using Clausena anisata leaf and Euphorbia abyssinica bark extracts and its comparative study of antibacterial activities

Green synthesis of metallic oxide nanoparticles has been used and preferred over physical and chemical methods of synthesis since it is a simple, inexpensive, and environmentally friendly method. This study aims to synthesize copper oxide nanoparticles that were successfully synthesized using Clausena anisata leaf and Euphorbia abyssinica bark by using copper sulphate pentahydrate (CuSO4·5H2O) as a precursor. The copper oxide nanoparticles were synthesized by using 2.5 mL of Clausena anisata leaf and the same amount of Euphorbia abyssinica bark extracts in 10 mL of a 15 mM CuSO4·5H2O solution using the green method. The synthesized copper oxide nanoparticles have been characterized by ultraviolet–visible (UV–Vis) absorption spectra, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), and scanning electron microscopy (SEM). The formation of copper oxide nanoparticles was confirmed by the UV–visible absorption spectrum in an intense surface plasmon resonance between 330 and 370 nm, which revealed the formation of copper oxide nanoparticles (CuO NPs). X-ray diffraction (XRD) spectra indicated the crystalline nature of CuO NPs. The average crystalline size of CuO NPs synthesized from Clausena anisata and Euphorbia abyssinica is 47.15 and 19.34 nm, respectively. The FT-IR results showed the existence of bioactive functional groups required for the reduction of copper ions, whereas the results of SEM confirm the green synthesized CuO NPs are spherical in shape. For antibacterial activity studies, the agar disk diffusion method was used. Anti-bacterial activities were studied against three different bacteria: Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli and Enterobacter cloacae) using CuO NPs (100–12.5 mg/mL). Ciprofloxacin and dimethyl sulphoxide, were used as positive and negative controls, respectively. Ciprofloxacin (60 µg/mL) inhibited Escherichia coli, Staphylococcus aureus, and Enterobacter cloacae with inhibition zones of 18, 20, and 25 mm, respectively. The CuO NPs synthesized from Euphorbia abyssinica bark showed higher anti-bacterial activity. Euphorbia abyssinica bark-mediated CuO NPs exhibited inhibition zones of 7, 11, and 13 mm against Escherichia coli, Enterobacter cloacae, and Staphylococcus aureus, respectively. Conversely, Clausena anisata leaf-mediated CuO NPs demonstrated inhibition zones of 8, 14, and 15 mm against the same microorganisms.