Synthesis of Chitosan and Its Complexes From Snail Shells: Development and Biological Evaluation of Biopesticide Applications

Abstract Pest control in modern agriculture relies heavily on synthetic pesticides, raising critical concerns about public health, environmental sustainability, and development of resistant pest species. As a viable alternative, this study aimed to synthesized chitosan-based biopesticides and its Cu (II) and Zn (II) complexes from Archachatina marginate shell and Achatina fulica shell. Chitosan was synthesized through sequential deproteinization, demineralization, and deacetylation of chitin using a published procedure. Physicochemical properties were assessed using standard methods. Further characterization of the chitosan and its complexes were conducted using FT-IR and UV-Vis. The resulting biopesticides were applied to maize weevils, and compared with chemical pesticide. Antimicrobial screening was performed using the agar well diffusion method. The chitosan obtained from Archachatina marginate shell and Achatina fulica shell yielded 75% and 70% with a pH of 7.0 and 6.9 respectively; the DD is 76% and 63% respectively. FT-IR spectra of both chitosan demonstrated hydroxyl and amide groups, the complexes show M-O and M-N band which was absent in the chitosan. The UV/Vis spectrum of both chitosan indicated the absorption peaks from 220 nm to 250 nm. n→π*intra ligand electronic transition was observed in both chitosan due to the C = O of the N-acetyl group in chitosan, which shifted to lower or higher wavelength in the complexes. Zn (II) and Cu (II) chitosan achieved 100% and 98% mortality rate against maize weevils respectively which was better compared to the chemical pesticide and control. Archachatina marginata shell chitosan shows higher antimicrobial activity compared to Achatina fulica shell chitosan.