Evaluation of the Effect of Chitosan/Cinnamon Essential Oil Hydrogel Formulation on Biochemical Traits (Total Phenol, Flavonoid, and Antioxidant Enzyme Activity) of Pepper Plant Against the Fungus Alternaria Solani

Abstract

This study evaluated the inhibitory effects of cinnamon essential oil, chitosan, and their combination against Alternaria solani, as well as their impact on disease severity, phenolic and flavonoid content, and the activity of defense-related enzymes peroxidase (POD) and superoxide dismutase (SOD). Based on the analysis of inhibitory percentages, the positive control, Cin.Ch. 500 ppm, and chitosan 600 ppm were identified as the most effective treatments for suppressing fungal growth, with mean inhibition rates of 93.66%, 93.33%, and 95.00%, respectively. Analysis of variance (ANOVA) revealed that treatment type, concentration, and their interaction significantly influenced disease severity (p < 0.05). The combined treatment of 600 ppm cinnamon and chitosan (Cin.Chi 600 ppm) showed the lowest mean disease severity (19.67), representing the most effective strategy for disease reduction. Regarding flavonoid and phenol content, treatment had a significant effect on flavonoids (F=550.501, p<0.001) and on phenols (F=3.538, p=0.038). Day significantly affected both flavonoids (F=23.530, p<0.001) and phenols (F = 46.506, p<0.001) and concentration parameter significantly affected flavonoids (F = 260.453, p < 0.001) and phenols (F=4.438, p=0.041). However, the interaction between treatment and concentration significantly affected flavonoids (F=19.621, p<0.001) but did not significantly affect phenols (F=2.638, p=0.106). Regarding defense enzymes, all treatments of cinnamon essential oil, chitosan, and their combination significantly affected POD and SOD activity, and the interaction between day and treatment also had a notable impact. Overall, the Cin.Chi 600 ppm treatment exhibited the greatest effect on both POD and SOD activity across the three examined days, indicating that increasing the concentration of both components to 600 ppm enhances the stimulation of defense enzyme activity. In conclusion, the application of Cin.Chi 600 ppm, incorporating both cinnamon and chitosan, serves as an effective strategy for enhancing POD and SOD defense enzyme activity, increasing flavonoid and phenol content, and reducing disease severity caused by Alternaria solani.