# Green Synthesis, Characterization, and Antifungal Efficiency of Biogenic Iron Oxide Nanoparticles
## 3 Results and Discussion
### Antifungal Efficacy of Standard Fungicide and Biogenic Iron Oxide Nanoparticles Against  
Different concentrations of the biogenic iron oxide nanoparticles (50, 100, 200, 400, and 800 ppm) were evaluated for their antifungal activity against the _A. alternata_ OR236467 and _A. alternata_ OR236468 strains utilizing the food poisoning technique (Figure 11). The commercial fungicide, namely, metalaxyl + mancozeb, at the concentration of 800 ppm revealed a higher antifungal efficiency against the _A. alternata_ OR236467 strain compared to the _A. alternata_ OR236468 strain, demonstrating relative growth inhibition percentages of 72.23 and 58.54%, respectively. Accordingly, the _A. alternata_ OR236468 strain showed a high resistance to the metalaxyl + mancozeb fungicide compared to the _A. alternata_ OR236467 strain. The antifungal efficiency of the biogenic IONPs synthesized using _L. nobilis_ extract (800 ppm) revealed a higher antifungal efficiency compared to the metalaxyl + mancozeb fungicide against the _A. alternata_ OR236467 strain, demonstrating relative growth inhibition percentages of 75.89 and 72.23%, respectively (Tables 2 and 3). Interestingly, the _A. alternata_ OR236468 strain revealed a higher level of susceptibility to the phytosynthesized IONPs in all of the tested concentrations compared to the metalaxyl + mancozeb fungicide. In the present study, the _A. alternata_ OR236468 strain exhibited a fungal growth diameter of 24.31 \(\pm\) 0.18 mm when exposed to a concentration of 800 ppm of the biogenic IONPs. This measurement was found to be significantly lower than the control, which had a fungal growth diameter of 58.63 \(\pm\) 0.43 mm. These results suggest that the biogenic IONPs are highly effective in inhibiting the growth of the tested strain, surpassing the efficacy of the metalaxyl + mancozeb fungicide. Furthermore, the fungal growth strain _A. alternata_ OR236467 exhibited a significant inhibition when subjected to treatment with the biogenic IONPs, as compared to the control group. Within this particular context, it is observed that the growth diameter experiences a reduction, specifically from a diameter of 78.35 \(\pm\) 0.16 mm in the control group to a diameter of 18.89 \(\pm\) 0.78 mm in the treatment group, subjected to 800 ppm of the biogenic IONPs. Collectively, the antifungal bioactivity of the biogenic IONPs was found to increase with the increasing concentration. The findings of our study align with those of a previous investigation that assessed the antifungal efficacy of the biogenic IONPs of _Oscillatoria linntica_ using the food poisoning technique. The prior report revealed that the higher concentrations of the biogenic IONPs exhibited a higher impact on the growth of fungal mycelium, with the greatest inhibition percentage observed at a concentration of 200 \(\upmu\)g/mL of the biogenic IONPs [64]. The biogenic IONPs synthesized using the leaf extract of _Parthenium hysterophorus_ were reported to possess antifungal effectiveness against the _A. dispersillus niger_ and _A. flavus_ strains [65]. Moreover, the antifungal efficiency of the biogenic IONPs synthesized using _Chorella_-K01 extract was confirmed against _Fusarium oxysporum_, _Fusarium manifilforme_, _Fusarium tricintcutum_, _Rhizoctonia solani_, and _Plythtium_ sp. [66]. Furthermore, the phyto-synthesized IONPs of _Laurus nobilis_ L. leaf extract revealed antifungal efficiency against the _A. dispersillus flavus_ and _Penicillium spinulosum_ strains [67]. Another study affirmed the antifungal efficiency of IONPs of _Euphoria herita_ leaf extract at a concentration range from 10 to 30 mg/mL against the _A. Aspergillus twinagatus_, _A. dispersillus niger_, and _Arthoghrophis cuboida_ strains [68]. Collectively, the biogenic IONPs synthesized using _L. nobilis_ extract was found to possess a potential antifungal efficiency at low concentrations of 50 and 100 ppm comparable to previous reports, indicating their potential use as natural fungicides, avoiding the harmful impact of synthetic chemical fungicides.