## 3 Results and Discussion
### Cytotoxicity Effect of Kakadu Plum Extract and KKD-ZnO-NPs  
According to our findings, we observed the cytotoxicity level of the Kakadu plum extract and KKD-ZnO-NPs on murine macrophage (RAW 264.7) cells and A549 lung cancer cells were medicated several concentrations (0, 2.5, 5, 10, 20 \(\mathrm{\SIUnitSymbolMicro g}\)/mL) for 24 h. In the cytotoxicity experiment, we used MTT solution for measuring the cell toxic level. Evaluation of the cytotoxicity in cancer-free RAW 264.7 cells was determined as safety of samples. It was observed that cell viability of RAW 264.7 cells was showed low toxicity with Kakadu plum extract and KKD-ZnO-NPs at 20 \(\mathrm{\SIUnitSymbolMicro g}\)/mL after 24 h (Figure 7A).  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Lattice Plane**} & **Position of** & **D Spacing** & **FWHM** & **Size (nm)** & **Average** \\  & **Peak (20)** & **Value (A\({}^{\circ}\))** & **Value (20)** & & **(nm)** \\ \hline
100 & 31.830 & 2.80915 & 0.4905 & 16.85 & \\
002 & 34.451 & 2.60116 & 0.2747 & 30.30 & \\
101 & 36.316 & 2.47176 & 0.4513 & 18.54 & \\
102 & 47.578 & 1.90966 & 1.025 & 8.48 & 21.89 \\
110 & 56.634 & 1.6239 & 0.7457 & 12.11 & \\
103 & 62.945 & 1.47543 & 0.9419 & 9.88 & \\
112 & 68.023 & 1.3771 & 0.8438 & 11.37 & \\ \hline \end{tabular}
\end{table}
Table 1: XRD analysis of the crystalline size of KKD-ZnO-NPs.  
Figure 6: XRD pattern of KKD-ZnO-NPs.  
On the other hand, it was observed that KKD-ZnO-NPs decreased A549 cell viability in a dose-dependent manner. Additionally, cytotoxicity determination was performed for KKD-ZnO-NPs compared to positive control such as commercial cisplatin, which is used as an anticancer drug. Results observed in Figure 7B, at the concentration of 10 \(\mathrm{\SIUnitSymbolMicro}\)/mL, KKD-ZnO-NPs had much higher toxicity than cisplatin. This study's cytotoxicity results are consistent with a previous report that observed _Mangifera indica_ leaves mediated ZnO-NPs, which could enhance the anticancer activity [50]. Moreover, there were several pieces of literature that reported the anticancer activity of ZnO nanoparticles [4; 9; 51; 52]. ZnO nanoparticles have the ability to dissolve Zn ions in the extracellular region by themselves, which in turn leads to increased intracellular Zn\({}^{2+}\) levels. ZnO-NPs are able to penetrate easily through the cell membrane to damage the mitochondrial and specific DNA sequences so that the medication significantly represses the growth of the tumor with the specific target location and specific cytotoxicity. Past examination detailed the anticancer impact of ZnO-NPs in cancer cells [53; 54]. Not only as reducing and stabilizing agents, but Kakadu plum extract could also enhance the anticancer effect on human lung cancer cell line (A549). Hence, the current investigation suggests that at a limit dosage (10 \(\mathrm{\SIUnitSymbolMicro}\)/mL), KKD-ZnO-NPs are effective as a cancer therapy drug with minimum toxicity.  
Figure 7: In vitro, cell cytotoxicity evaluation for Kakadu plum extract and KKD-ZnO-NPs (**A**) on murine macrophage (RAW 264.7), (**B**) on human lung carcinoma (A549) cells compared to positive control (cisplatin). Graph shows mean \(\pm\) SD values of four replicates. **\(p<0.01\); ***\(p<0.001\)** indicates significant differences from control groups.