The toxicity risks, instability of essential oil, and complex composition are principal obstacles to using essential plant oil for clinical applications. Solving stability-related problems, providing targeted drug delivery, and decreasing plant essential oil toxicity, encapsulation can be used successfully. Rosemary (Rosmarinus officinalis) is a perennial plant of the Lamiaceae family with various healing properties. However, the rosemary essential oil, as volatile oil, is fast evaporated, which limits its applications. This study’s goal is to boost the prevent evaporation and bioactivity of rosemary essential oil by developing zein-NPs as a promising NDS (nano-drug-delivery system) and assessing the effect of NPs on the rosemary essential oil efficacy. Scanning electron microscopy (SEM) showed NPs sizes between 70–200 nm. With dynamic light scattering analysis (DLS), the average size of zein nanoparticle-containing rosemary essential oil (NPZLA) was obtained at ca. 154.5 nm. The entrapment efficiency (EE) on rosemary essential oil was ca. 71% inside the zein NPs. The in vitro release suggests that the polymeric barrier can control the rosemary essential oil release. Zein-NPs can be potentially used as NC (nanocarrier) for enhancing the evaporation inhibitor of ether oil of rosemary essential oil to enhance its bioavailability and performance further. It can be concluded that rosemary plant can be used as the core inside the nanoparticle by biological production method due to its medicinal properties and other properties. Based on the stated content, it is clear that in the future, by conducting more extensive research, the necessary platform can be provided for the use of this medicinal plant as much as possible in the pharmaceutical industry.
