Nature-inspired ZnO nanoparticles: unlocking the biomedical potential of Glycyrrhiza glabra-mediated green synthesis through in vitro and in silico approaches

Abstract

In this research work, the aqueous root extract of Glycyrrhiza glabra (G. glabra) was used to synthesize phytoconstituent-coated zinc oxide nanoparticles (ZnONPs) for the first time. The plant extract served as a reducing and coating/stabilizing agent. The alteration in the physicochemical properties and biomedical potential of the synthesized ZnONPs with an increase in the volume of G. glabra extract was investigated, making this study different from others. X-ray diffraction (XRD) analysis confirms that the average crystallite size of the nanoparticles decreased with an increase in the plant extract volume. Field-emission scanning electron microscopy (FESEM) analysis confirmed the formation of uniform spherical particles for all three samples, while energy-dispersive X-ray (EDX) analysis revealed their elemental composition. The samples showed excellent antibacterial activity against Gram-positive Streptococcus mutans and Gram-negative Escherichia coli with the highest zone of inhibition values of 19.33 ± 0.47 and 25 ± 0.81 mm, respectively. In silico molecular docking studies were also performed against two different receptors, i.e., DNA gyrase B (E. coli) and antigen-I/II carboxy-terminus (S. mutans) proteins with several phytoconstituents (identified through gas chromatography-mass spectroscopy (GC-MS) analysis). Among the four phytoconstituents, 9,12-octadecadienoic acid (Z,Z)- (−5.5, and −4.8 kcal mol⁻¹) and n-hexadecanoic acid (−5.5 and −4.5 kcal mol⁻¹) exhibited the highest binding affinity. The molecular docking outcome demonstrates good agreement with the in vitro result. Additionally, the cell viability of the as-synthesized ZnONPs against a normal cell line (HaCaT) was >95% compared to the cell viability against cancer cells (69.5% ± 3.8%), which indicates that the sample has higher selectivity towards cancer cells. Subsequently, the minimal toxicity of the phytochemical-coated ZnONPs enhances their suitability across diverse biomedical fields, especially in combating bacterial infections.