Biosynthesis of CuO nanoparticle using leaf extracts of Ocimum lamiifolium Hochst. ex Benth and Withana somnifera (L) Dunal for antibacterial activity

Abstract

Nanotechnology is becoming a promise for scientific advancement nowadays in areas like medicine, consumer products, energy, materials, and manufacturing. Copper oxide nanoparticles (CuO NPs) were synthesized using Ocimum lamiifolium Hochst. ex Benth and Withana somnifera (L) Dunal leaf extract via green synthetic pathway. The leaf of O. lamiifolium and W. somnifera were known to have strong antibiotic and antioxidant properties arising due to the presence of various secondary metabolites, including, flavonoids, alkaloids, saponins, tannins, cardiac glycosides, and phenolic compounds which serve as reducing, stabilizing, and capping agents for the CuO-Nanoparticles (NPs) synthesized. The biosynthesized CuO NPs were characterized based on Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, and scanning electron microscopy. O. lamiifolium and W. somnifera leaf extract mediated synthesis could produce CuO NPs with average crystallite size of 15 nm and 19 nm, respectively. The biosynthesized CuO-NPs were further examined for antibacterial activity with Gram-positive (S. aureus) and Gram-negative bacteria (E. coli and P. aeruginosa). The GZDK-CuO NPs synthesized using W. somnifera leaf extract inhibited the growth of E. coli. and P. aeruginosa largely in comparison to S. aureus. Whereas the DMAZ-CuO NPs synthesized with the help of O. lamiifolium leaf extract showed higher bacterial inhibition on E. coli compared to S. aureus and P. aeruginosa. The minimum inhibitory concentration (MIC) values of both types of NPs are also assessed on all three pathogens. The newly biosynthesized nanoparticles, thus, were found to be optional materials for inhibiting the growth of drug- resistant bacterial pathogens.

Keywords: Antibacterial activity; Green synthesis; Nanotechnology; Phytochemicals.

Fig. 1

Schematic diagram showing the synthesis of CuO NPs from W. somnifera (L) Dunal and O.lamiifolium Hochest.ex.Benth aqueous leaf extract, characterization, and use in antibacterial activity.

Fig. 2

X-ray diffraction patterns of GZDK-CuO NPs (a), DMAZ-CuO NPs (b) and CuO NPs calculated from CCDC 1,602,101.

Fig. 3

FT-IR spectra of GZDK -CuO NPs and DMAZ- CuO NPs.

Fig. 4

Tauc plot of biosynthesized CuO NPs using (a) O. lamiifolium and (b) W. somnifera leaf extracts, respectively.

Fig. 5

SEM images of (A) DMAZ- CuO NPs and (B) GZDK- CuO NPs.

Fig. 6

Disc diffusion observed when bacterial strains are treated with different concentration of GZDK- CuO NPs against (a) S. aureus, (b) P. aeruginosa and (c) E.coli; DMAZ-CuO NPs against (d) S. aureus, (e) P. aeruginosa and (f) E.coli.

Fig. 7

Zone of inhibition when different concentration of (a) GZDK-CuO NPs and (b) DMAZ- CuO NPs are treated with S. aureus, P. aeruginosa and E.coli. Error bars represent deviations from the mean, with significant differences at p < 0.05.

Fig. 8

MIC vale for GZDK-CuO NPs (a) and DMAZ-CuO NPs (b) against S. aureus, Ecoli and P. aeruginosa. Error bars represent deviations from the mean, with significant differences at p < 0.05.