The study determined the in vitro antioxidant potential of zinc oxide nanoparticles (ZnONPs) and inhibitory properties of ZnONPs-ciprofloxacin nanoconjugate on the activity of dehydrogenase enzyme from multi-drug resistant Staphylococcus aureus (MRSA). Rauwolfia vomitoria (SW) leaf extract was used for the synthesis of the ZnONPs. Volatile phytochemical constituents of the leaf extract were assessed using Gas Chromatography-Mass Spectrometry (GC–MS) which confirmed fifteen volatile phytochemicals with phytol (39.99 %) being the most abundant and the least being 4-hydoxy-3-methylacetophenone (0.85 %). The ZnONPs were characterized with UV–Vis spectroscopy, Energy Dispersive X-ray Spectroscopy (EDX), Scanning Electron Microscopy (SEM), and Transmission Electrron Microscopy (TEM). The UV–Vis results showed maximum light absorption at a wavelength of 300 nm whereas EDS revealed 64.84 % Zn, 18.88 % O, and 16.28 % C. The microscopic studies gave agglomerated spherical zinc nanoparticles with average size of 99.02 nm. The free radical scavenging ability showed weaker properties for the ZnONPs compared to the control and the leaf extract. At 30 mg/mL, the nanoconjugates significantly (p < 0.05) recorded 100 % inhibition of the enzyme activities. The inhibitory properties of the antimicrobial agents indicated that ZnONPs-ciprofloxacin > ZnONPs > R. vomitoria leaf extract. The ZnONPs-ciprofloxacin nanoconjugate expressed mild dose–response inhibitory relationship (R2 = 0.66) against the MRSA dehydrogenase activity at the IC50 of 2.93 mg/mL. © 2023 Elsevier B.V.