title: Enhancement of fungicidal and insecticidal activity by reductive alkylation of chitosan.
abstract: A series of N-alkyl chitosan (NAC) derivatives were synthesized using a reductive alkylation reaction to examine their fungicidal and insecticidal activity. The chemical structures were characterized by IR and (1)H NMR spectroscopy, and the degree of substitution (DS) ranged from 0.02 to 0.37. Their fungicidal activity was evaluated against the grey mould Botrytis cinerea Pers ex Fr (Leotiales: Sclerotiniaceae) and the rice leaf blast pathogen Pyricularia grisea Sacc [Teleomorph: Magnaporthe grisea (Hebert) Barr] by a radial growth bioassay. It was of interest that most of the NAC derivatives were more active against both fungi than chitosan itself. The most active derivative was N-(2,2-diphenylethyl)chitosan with EC50 values of 0.031 and 0.23 g L(-1) against B. cinerea and P. grisea respectively. In addition, some derivatives, at higher concentrations up to 1.0 g L(-1), inhibited the mycelial growth and spore formation of P. grisea. Bioassays against larvae of the cotton leafworm, Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) with the NAC derivatives at a rate of 5.0 g kg(-1) in artificial diet demonstrated that N-(3-phenylbutyl)chitosan was the most active compound. In addition, N-propylchitosan, N-undecanylchitosan and N-(3-phenylpropyl)chitosan derivatives strongly inhibited larval weight gain in S. littoralis, with respective reductions of 76, 66 and 65% after 4 days of feeding on treated diet.
authors.affiliation: Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Coupure Links 653, B-9000 Ghent, Belgium.
authors.forename: Entsar I
authors.initials: EI
authors.lastname: Rabea
authors.forename: Mohamed
authors.initials: M
authors.lastname: El Badawy
authors.forename: Tina M
authors.initials: TM
authors.lastname: Rogge
authors.forename: Christian V
authors.initials: CV
authors.lastname: Stevens
authors.forename: Walter
authors.initials: W
authors.lastname: Steurbaut
authors.forename: Monica
authors.initials: M
authors.lastname: Höfte
authors.forename: Guy
authors.initials: G
authors.lastname: Smagghe
mesh_terms: D000478:Alkylation; D000818:Animals; D001203:Ascomycota / Q000187:drug effects; D020171:Botrytis / Q000187:drug effects; D048271:Chitosan / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000633:toxicity*; D005659:Fungicides, Industrial; D007306:Insecticides; D007814:Larva / Q000502:physiology; D019906:Nuclear Magnetic Resonance, Biomolecular; D018411:Spodoptera / Q000502:physiology
chemical_list: D005659:Fungicides, Industrial; D007306:Insecticides; D048271:Chitosan