Methylated N-aryl chitosan derivative/DNA complex nanoparticles for gene delivery: Synthesis and structure–activity relationships

In this study, three kinds of methylated chitosan containing different aromatic moieties were synthesized by two steps, reductive amination and methylation, respectively. The chemical structures of all methylated derivatives, methylated N-(4-N,N-dimethylaminocinnamyl) chitosan chloride (MDMCMChC), methylated N-(4-N,N-dimethylaminobenzyl) chitosan chloride (MDMBzChC), and methylated N-(4-pyridinylmethyl) chitosan chloride (MPyMeChC) were characterized by ATR–FTIR and ¹H NMR spectroscopy. The complexes between the chitosan derivatives and plasmid DNA at different N/P ratios were characterized by gel electrophoresis, dynamic light scattering, and atomic force microscopic techniques. The smallest particle sizes of these complexes were obtained at N/P ratio of 5 and ranged from 95 to 124 nm while the zeta-potentials were in the range of 18–27 mV. Transfection efficiencies of these complexes were investigated by expression of the plasmid DNA encoding green fluorescence protein (pEGFP-C2) on human hepatoma cells (Huh 7 cells) compared to N,N,N-trimethyl chitosan chloride (TMChC). The rank of transfection efficiency was MPyMeChC > MDMBzChC > TMChC > MDMCMChC, respectively. The cytotoxicity of these complexes was also studied by MTT assay where the MPyMeChC complex exhibited less toxicity than other derivatives even at high N/P ratios. Therefore, MPyMeChC demonstrated potential as its safe and efficient gene carrier.     

Methylated N-(4-N,N-Dimethylaminobenzyl) Chitosan, a Novel Chitosan Derivative, Enhances Paracellular Permeability Across Intestinal Epithelial Cells (Caco-2)

The aim of this study was to investigate the effect of methylated N-(4-N,N-dimethylaminobenzyl) chitosan, TM-Bz-CS, on the paracellular permeability of Caco-2 cell monolayers and its toxicity towards the cell lines. The factors affecting epithelial permeability, e.g., degree of quaternization (DQ) and extent of dimethylaminobenzyl substitution (ES), were evaluated in intestinal cell monolayers of Caco-2 cells using the transepithelial electrical resistance and permeability of Caco-2 cell monolayers, with fluorescein isothiocyanate dextran 4,400 (FD-4) as a model compound for paracellular tight-junction transport. Cytotoxicity was evaluated with the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide viability assay. The results revealed that, at pH 7.4, TM-Bz-CS appeared to increase cell permeability in a concentration-dependent manner, and this effect was relatively reversible at lower doses of 0.05–0.5 mM. Higher DQ and the ES caused the permeability of FD-4 to be higher. The cytotoxicity of TM-Bz-CS depended on concentration, %DQ, and %ES. These studies demonstrated that this novel modified chitosan has potential as an absorption enhancer.     

Synthesis and characterization of chitosan-homocysteine thiolactone as a mucoadhesive polymer

Two mucoadhesive thiolated polymers were synthesized by the covalent attachment of homocysteine thiolactone (HT) to chitosan and N,N,N-trimethyl-chitosan (TM-chitosan) at various chitosan:HT ratios. The amount of thiol and disulphide groups immobilized on the chitosan influenced the polymer's mucoadhesion positively and negatively, respectively, with the optimal chitosan:HT (w/w) ratio being found to be 1:0.1. The interaction between mucin and chitosan and its three derivatives was highest for the thiolated chitosan derivatives but was pH dependent. HT-chitosan and TM-HT-chitosan, with the thiol groups of 64.15 and 32.48 μmol/g, respectively, displayed a 3.67- and 6.33-fold stronger mucoadhesive property compared to that of the unmodified chitosan at pH 1.2, but these differences were only ∼1.7-fold at pH 6.4. The swelling properties of TM-HT-chitosan and HT-chitosan were higher than that of chitosan and TM-chitosan, attaining a swelling ratio of up to 240% and 140%, respectively, at pH 1.2 within 2 h.     

Antibacterial activity of quaternary ammonium chitosan containing mono or disaccharide moieties: Preparation and characterization

The 9 quaternary ammonium chitosans containing monosaccharides or disaccharides moieties were successfully synthesized by reductive N-alkylation then quaternized by N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (Quat-188). The chemical structures of quaternary ammonium chitosan derivatives were characterized by ATR-FTIR and ¹H NMR spectroscopy. The degree of N-substitution (DS) and the degree of quaternization (DQ) were determined by ¹H NMR spectroscopic method. It was found that the DS was in the range of 12–40% while the DQ was in the range of 90–97%. The results indicated that the O-alkylation was occured in this condition. Moreover, all quaternary ammonium chitosan derivatives were highly water-soluble at acidic, basic, and neutral pH. Minimum inhibitory concentration (MIC) antibacterial studies of these materials were carried out on Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria compared to quaternary ammonium N-octyl and N-benzyl chitosan derivatives. The quaternary ammonium mono and disaccharide chitosan derivatives showed very high MIC values which were in the range of 32 to >256 μg/mL against both bacteria. Also it was found that the antibacterial activity decreased with increasing the DS. This was due to the increased hydrophilicity of mono and disaccharide moieties. On the other hand, the low MIC values (8–32 μg/mL) were obviously observed when the DS of quaternary ammonium N-octyl and N-benzyl chitosan derivatives was lower than 18%. The results showed that the presence of hydrophobic moiety such as the N-benzyl group enhanced the antibacterial activity compared to the hydrophilic moiety against both bacteria.     

Preparation,Statistical Optimization,and <Emphasis Type="Italic">In vitro</Emphasis> Characterization of Insulin Nanoparticles Composed of Quaternized Aromatic Derivatives of Chitosan

The aim of this study was the preparation, optimization, and in vitro characterization of insulin nanoparticles composed of methylated N-(4-N,N-dimethylaminobenzyl), methylated N-(4-pyridinyl), and methylated N-(benzyl) chitosan. Three types of derivatives were synthesized by the Schiff base reaction followed by quaternization. Nanoparticles were prepared by the polyelectrolyte complexation method. Experimental design D-optimal response surface methodology was used for the optimization of the nanoparticles. Independent variables were pH of polymer solution, concentration ratio of polymer/insulin, and also polymer type. Dependent variables include size, zeta potential, polydispersity index (PdI), and entrapment efficiency (EE%). Optimized nanoparticles were studied morphologically by transmission electron microscopy (TEM), and in vitro release of insulin from nanoparticles were determined under phosphate buffer (pH = 6.8) condition. Although a quadratic model has been chosen to fit the responses for size, PdI, and EE%, the zeta potential of the particles has been best fitted to 2-FI model. The optimized nanoparticles were characterized. The size of the particles were found to be 346, 318, and 289 nm; zeta potentials were 28.5, 27.7, and 22.2 mV; PdI of particles were 0.305, 0.333, and 0.437; and calculated EE% were 70.3%, 84.5%, and 69.2%, for methylated (aminobenzyl), methylated (pyridinyl), and methylated (benzyl) chitosan nanoparticles, respectively. TEM images show separated and non-aggregated nanoparticles with sub-spherical shapes and smooth surfaces. An in vitro release study of the prepared nanoparticles showed that the cumulative percentage of insulin released from the nanoparticles were 47.1%, 38%, and 68.7% for (aminobenzyl), (pyridinyl), and (benzyl) chitosan, respectively, within 300 min.     

Synthesis, characterization, and antibacterial activity of N,O-quaternary ammonium chitosan

N,N,N-Trimethyl O-(2-hydroxy-3-trimethylammonium propyl) chitosans (TMHTMAPC) with different degrees of O-substitution were synthesized by reacting O-methyl-free N,N,N-trimethyl chitosan (TMC) with 3-chloro-2-hydroxy-propyl trimethyl ammonium chloride (CHPTMAC). The products were characterized by ¹H NMR, FTIR and TGA, and investigated for antibacterial activity against Staphylococcus aureus and Escherichia coli under weakly acidic (pH 5.5) and weakly basic (pH 7.2) conditions. TMHTMAPC exhibited enhanced antibacterial activity compared with TMC, and the activity of TMHTMAPC increased with an increase in the degree of substitution. Divalent cations (Ba²⁺ and Ca²⁺) strongly reduced the antibacterial activity of chitosan, O-carboxymethyl chitosan and N,N,N-trimethyl-O-carboxymethyl chitosan, but the repression on the antibacterial activity of TMC and TMHTMAPC was weaker. This indicates that the free amino group on chitosan backbone is the main functional group interacting with divalent cations. The existence of 100 mM Na⁺ slightly reduced the antibacterial activity of both chitosan and its derivatives.     

Synthesis of a series of fully methylated aldobiouronic acids,and β-elimination reactions of their synthetic precursors

Treatment of methyl 2,3,4-tri-O-acetyl-l-bromo-l-deoxy-α-d-glucopyranuronate severally with 2,4,6-, 2,3,6-, and 2,3,4-tri-O-methyl derivatives of methyl α-d-glucopyranoside and with methyl 4,6-O-benzylidene-3-O-methyl-α-d-glucopyranoside, in the presence of silver carbonate, afforded crystalline aldobiouronic acid derivatives in high yield. Deacetylation followed by methylation gave a series of fully methylated derivatives of laminaribiouronic, cellobiouronic, and gentiobiouronic acids, and the (1 → 2)-linked analogue. Methylation with methyl iodide and silver oxide in N,N-dimethylformamide was invariably accompanied by a small amount ofβ-elimination, with the formation of olefinic disaccharides which were also obtained by β-elimination reactions of the precursor acetates followed by methylation. Methyl 4,5-unsaturated 4-deoxyhexopyranosyluronate derivatives were the main products of the reaction, but these underwent further degradation with cleavage of the interglycosidic linkage and formation of 6-methoxycarbonyl-4-pyrone.     

Self-aggregates formation and mucoadhesive property of water-soluble β-cyclodextrin grafted with chitosan

Water-soluble β-cyclodextrin grafted with chitosan (CD-g-CS) was carried out by quaternizing the CD-g-CS with glycidyltrimethyl ammonium chloride (GTMAC) under mild acidic condition, corresponding to the quaternized CD-g-CS (QCD-g-CS). The degrees of substitution (DS) and quaternization (DQ), ranging from 5% to 23% and 66% to 80%, respectively, were determined by (1)H NMR spectroscopy. Self-aggregates formation of all QCD-g-CSs were investigated in water using dynamic light scattering (DLS), atomic force microscopy (AFM), and transmission electron microscopy (TEM) techniques. The result revealed that all QCD-g-CSs are able to form self-aggregates in water. Large particle sizes ranged from 800 to 3000nm were obtained by DLS while zeta-potentials were ranging from 25 to 40mV. AFM and TEM depicted a spherical shape with particle sizes ranging from 100 to 900nm. Mucoadhesive and cytotoxic properties of all QCD-g-CSs were evaluated using a mucin particle method and MTT assay compared to quaternized chitosan (QCS). It was found that the mucoadhesive property increased with decreasing DS due to less quaternary ammonium moiety into the chitosan backbone. On the other hand, the cytotoxicity increased with increasing DS even though the DQ is decreased.     

Tissue-specific biosynthesis of epsilon-N-monomethyllysine and epsilon-N-trimethyllysine in skeletal and cardiac muscle myosin: a model for the cell-free study of post-translational amino acid modifications in proteins.

As a continuation of the study on post-ribosomal amino acid modifications in myosin, the regulation of tissue-specific biosynthesis of ϵ-N-monomethyllysine and ϵ-N-trimethyllysine was investigated. While ϵ-N-trimethyllysine is a component of both skeletal and cardiac muscle myosins, in certain species the monomethylated amino acids occur only in myosin from skeletal muscle. The methylation of skeletal and cardiac muscle myosin with cardiac or skeletal muscle enzymes was expected to elucidate whether the tissue-specific occurrence of the ϵ-N-monomethyllysine is related to the structure of skeletal and cardiac myosin or to the existence of the methylating enzyme in the skeletal and cardiac muscle cells. The experimental approach is based on cell-free methylation of lysines at 24 °C, at which temperature the myosin chains remain polysome-bound. The methylated myosin was digested with trypsin and the radioactive methyl group-containing peptides were fractionated with ion-exchange chromatography. The peptide peaks with radioactivity were subjected to amino acid analyses and the radioactive methylated lysine derivatives were identified. ϵ-N-trimethyllysine was found in hydrolysates of all the methylated myosins, and ϵN-monomethyllysine was also present in both skeletal and cardiac muscle myosin if they were incubated with skeletal muscle supernatant. Thus the experimental results agree with our earlier suggestion (Huszar &; Elzinga, 1972) that the lack of a certain methylated amino acid in cardiac muscle myosin is due to the absence of the methylating enzyme rather than to differences in the structure of cardiac versus skeletal myosin. The experimental design developed for this work should be useful to study post-translational modifications in proteins, as well as to investigate muscle and other diseases in which the post-translational processing of proteins contributes to the dys function.     

Methylated N-(4-N,N-dimethylaminobenzyl) chitosan as effective gene carriers: Effect of degree of substitution

The objective of this study was to investigate the transfection efficiency of quaternized N-(4-N,N-dimethylaminobenzyl) chitosan; TM-Bz-CS, using the plasmid DNA encoding green fluorescent protein (pEGFP-C2) on human hepatoma cell lines (Huh7 cells). The factors affecting the transfection efficiency e.g. degree of quaternization (DQ), the degree of dimethylaminobenzyl substitution (DS) and polymer/DNA weight ratio, have been evaluated. The results revealed that all TM-Bz-CS derivatives were able to condense with DNA. Illustrated by agarose gel electrophoresis, complete complexes of TM₅₇-Bz₄₂-CS/DNA were formed at weight ratio of above 0.5, whereas those of TM₄₇-Bz₄₂-CS/DNA and TM₅₇- Bz₁₇-CS/DNA were above 1. The rank of transfection efficiency of the chitosan derivatives were TM₅₇-Bz₄₂-CS > TM₄₇-Bz₄₂-CS > TM₅₇-Bz₁₈-CS. The pH of culture medium did not affect the transfection efficiency of TM₅₇-Bz₄₂-CS/DNA complex, whereas it affected the transfection efficiency of chitosan/DNA complex. The results indicated that the improved gene transfection was due to the hydrophobic group (N,N-dimethylaminobenzyl) substitution on chitosan which promoted the interaction and condensation with DNA as well as N-quaternization which increased chitosan water solubility and enhance gene expression. For cytotoxicity studies, TM-Bz-CS was safe at the concentration of the highest transfection. In conclusion, this novel chitosan derivative, TM₅₇-Bz₄₂-CS showed elevated potential as gene carrier by efficient DNA condensation and mediated highest level of gene transfection with negligible cytotoxicity in Huh7 cells.     

Stereochemistry of the Reductive Amination of 4-Oxoproline Derivatives with Glycine Esters

An amination of 4-oxoproline derivatives with glycine methyl or benzyl ester and sodium cyanoborohydride led to the mixtures of corresponding diastereomeric 4-cis- and 4-trans-glycinoproline derivatives. We found that the ratio of diastereomers mainly depends on the structure of 4-oxoproline ester groups and, to a lesser extent, on the structure of N-acyl substituents. The best results were achieved with tert-butyl ester group; it ensured good yields of the amination products and the greatest prevalence of 4-cis-isomers. The structure of ester group in glycine molecule only scarcely affected the resulting ratio of N-(N-benzyloxycarbonylglycyl)-4-glycinoprolines.     

Antifungal property of quaternized chitosan and its derivatives

Five water-soluble chitosan derivatives were carried out by quaternizing either iodomethane or N-(3-chloro-2-hydroxypropyl) trimethylammonium chloride (Quat188) as a quaternizing agent under basic condition. The degree of quaternization (DQ) ranged between 28 ± 2% and 90 ± 2%. The antifungal activity was evaluated by using disc diffusion method, minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC) methods against Trichophyton rubrum (T. rubrum), Trichophyton mentagrophyte (T. mentagrophyte), and Microsporum gypseum (M. gypseum) at pH 7.2. All quaternized chitosans and its derivatives showed more effective against T. rubrum than M. gypseum and T. mentagrophyte. The MIC and MFC values were found to range between 125-1000 μg/mL and 500-4000 μg/mL, respectively against all fungi. Our results indicated that the quaternized N-(4-N,N-dimethylaminocinnamyl) chitosan chloride showed highest antifungal activity against T. rubrum and M. gypseum compared to other quaternized chitosan derivatives. The antifungal activity tended to increase with an increase in molecular weight, degree of quaternization and hydrophobic moiety against T. rubrum. However, the antifungal activity was depended on type of fungal as well as chemical structure of the quaternized chitosan derivatives.     

Preparation of 1-C-glycosyl aldehydes by reductive hydrolysis

Reductive hydrolysis of various protected glycosyl cyanides was carried out using DIBAL-H to form aldimine alane intermediates which were then hydrolyzed under mildly acidic condition to provide the corresponding aldehyde derivatives. While 1-C-formyl glycal and 2-deoxy glycosyl derivatives were stable during isolation and storage 1-C-glycosyl formaldehydes in the gluco, galacto and manno series were sensitive and decomposition occurred by 2-alkyloxy elimination. A one-pot method using N,N′-diphenylethylenediamine to trap these aldehydes in stable form was developed. Reductive hydrolysis of glycosyl cyanides offers valuable aldehyde building blocks in a convenient way which can be applied in the synthesis of complex C-glycosides.     

Mucoadhesive Bilayered Patches for Administration of Sumatriptan Succinate

The purpose of this study was to develop and optimize formulations of mucoadhesive bilayered buccal patches of sumatriptan succinate using chitosan as the base matrix. The patches were prepared by the solvent casting method. Gelatin and polyvinyl pyrrolidone (PVP) K30 were incorporated into the patches, to improve the film properties of the patches. The patches were found to be smooth in appearance, uniform in thickness, weight, and drug content; showed good mucoadhesive strength; and good folding endurance. A 3² full factorial design was employed to study the effect of independent variables viz. levels of chitosan and PVP K30, which significantly influenced characteristics like swelling index, in-vitro mucoadhesive strength, in vitro drug release, and in-vitro residence time. Different penetration enhancers were tried to improve the permeation of sumatriptan succinate through buccal mucosa. Formulation containing 3% dimethyl sulfoxide showed good permeation of sumatriptan succinate through mucosa. Histopathological studies revealed no buccal mucosal damage. It can be concluded that buccal route can be one of the alternatives available for administration of sumatriptan succinate.     

Synthesis of functionalized amino acid derivatives as new pharmacophores for designing anticancer agents

A new series of functionalized amino acid derivatives N-substituted 1-N-(tert-butoxycarbonyl)-2,2-dimethyl-4-phenyl-5-oxazolidine carboxamide (1-17) and 1-N-substituted-3-amino-2-hydroxy-3-phenylpropane-1-carboxamide (18-34) were synthesized and evaluated for their in vitro cytotoxicity against human cancer cell lines. Compound 6 has shown interesting cytotoxicity (IC₅₀ = 5.67 μm) in ovarian cancer, while compound 10 exhibited promising cytotoxicity in ovarian (IC₅₀ = 6.1 μm) and oral (IC₅₀ = 4.17 μm) cancers. These compounds could be of use in designing new anti-cancer agents.     

Improved synthesis and the crystal structure of methyl 4,6-dideoxy-4-(3-deoxy- -glycero-tetronamido)-α- -mannopyranoside, the methyl α-glycoside of the intracatenary repeating unit of the O-polysaccharide of Vibrio cholerae O:1

The crude product of deamination of the commercially available -homoserine was acetylated and the 2-O-acetyl-3-deoxy- -glycero-tetronolactone (18) formed was used to N-acylate methyl perosaminide (methyl 4-amino-4,6-dideoxy-α- -mannopyranoside, 12) and its 2,3-O-isopropylidene derivative. The major product isolated from the reaction was the crystalline methyl 4-(4-O-acetyl-3-deoxy- -glycero-tetronamido)-4,6-dideoxy-α- -mannopyranoside (1, 70–75%) resulting from acetyl group migration in the initially formed 2'-O-acetyl derivative. O-Deacetylation of 1 gave the title amide 2. Compound 2, obtained crystalline for the first time, was fully characterized, and its crystal structure was determined. Deoxytetronamido derivatives diastereomeric with 1 and 2, respectively, were obtained by the acylation of 12 with 2-O-acetyl-3-deoxy- -glycero-tetronolactone (prepared from -homoserine), and subsequent deacetylation. Structures of several byproducts of the reaction of 12 with 18 have been deduced from their spectral characteristics. Since these byproducts were various O-acetyl derivatives of 2, the title compound could be obtained in ≈ 90% yield by deacetylating (Zemplén) the crude mixture of N-acylation products, followed by chromatography.     

<Emphasis Type="Italic">In vitro</Emphasis> Permeability Enhancement in Intestinal Epithelial Cells (Caco-2) Monolayer of Water Soluble Quaternary Ammonium Chitosan Derivatives

The aim of this study was to investigate the effects of a type of hydrophobic moiety, extent of N-substitution (ES), and degree of quaternization (DQ) of chitosan (CS) on the transepithelial electrical resistance and permeability of Caco-2 cells monolayer, using fluorescein isothiocyanate dextran 4,400 (FD-4) as the model compound for paracellular tight junction transport. CS was substituted with hydrophobic moiety, an aliphatic aldehyde (n-octyl) or aromatic aldehyde (benzyl), for the improved hydrophobic interaction with cell membrane, and they were quaternized with Quat-188 to render CS soluble. The factors affecting the epithelial permeability have been evaluated in the intestinal cell monolayers, Caco-2 cells. Cytotoxicity was evaluated by using the trypan blue and MTT viability assay. The results revealed that at pH 7.4 CSQ appeared to increase cell permeability in dose-dependent manner, and this effect was relatively reversible at the lower doses of 0.05–1.25 mM. The higher DQ and ES caused the higher permeability of FD-4. Cytotoxicity of CSQ was concentration, %DQ, and %ES dependent. Substitution with hydrophobic moiety caused decreasing in permeability of FD-4 and cytotoxicity by benzyl group had more effect than octyl group. These studies demonstrated that these novel modified chitosan derivatives had potential for using as absorption enhancers.     

Synthesis and antiproliferative activity of some steroidal lactams

Using cholesterol as starting material, a series of 6-substituted-3-aza-A-homo-3-oxycholestanes and 6-substituted-4-aza-A-homo-3-oxycholestanes were synthesized by the oxidation, reduction, oximation, Beckman rearrangement and condensation reaction. These synthesized compounds displayed a distinct cytotoxicity against MGC 7901, HeLa and SMMC 7404 cancer cells. Our results revealed that the structures of functional groups at position-6 on the steroidal ring are crucial for the IC₅₀ value of antiproliferative activities of these compounds and the cytotoxic activity against MGC 7901 and SMMC 7404 cells was not significantly different between 4-N-lactams and 3-N-lactams when its 6-substituted group was a carbonyl or a hydroximino, but all 3-N-lactams showed a higher cytotoxicity against HeLa cells than 4-N-lactams. In particular, compounds 6, 8, 9 (IC₅₀6: 6.5 μmol/L; 8: 7.7 μmol/L; 9: 5.6 μmol/L) were even more cytotoxic than cisplatin to HeLa cells (positive contrast, 10.1 μmol/L). The information obtained from the studies may be useful for the design of novel chemotherapeutic drugs.     

Enhanced production of laccase in the fungus Trametes versicolor by the addition of xenobiotics

Agrochemicals, industrial compounds and their transformation products have been assayed for their ability to enhance laccase production in liquid cultures of Trametes versicolor, when added at 0.5 mM. After 3 days of treatment, enzymatic activity in the culture medium was increased 14-fold by 4-n-nonylphenol and 24-fold by aniline. Laccase activity was enhanced 10-fold by oxidised derivatives of the herbicide diquat, 17-fold by N,N-dimethyl-N-(5-chloro,4-hydroxyphenyl)urea and 22-fold by 9-fluorenone.     

The effect of size and acetylation degree of chitosan derivatives on tobacco plant protection against Phytophthora parasitica nicotianae

Enzymatic degradation of chitosan polymer with Pectinex Ultra SPL was used to obtain derivatives with biological potential as protective agents against Phytophthora parasitica nicotianae (Ppn) in tobacco plants. The 24 h hydrolysate showed the highest Ppn antipathogenic activity and the chitosan native polymer the lowest. The in vitro growth inhibition of several Phytophthora parasitica strains by two chitosans of different DA was compared. While less acetylated chitosan (DA 1%) fully inhibited three P. parasitica strains at the doses 500 and 1000 mg/l the second polymer (DA 36.5%) never completely inhibited such strains. When comparing two polymers of similar molecular weight and different DA, again the highest antipathogenic activity was for the less acetylated polymer. However, degraded chitosan always showed the highest pathogen growth inhibition. Additionally, a bioassay in tobacco seedlings to test plant protection against Ppn by foliar application demonstrated that partially acetylated chitosan and its hydrolysate induced systemic resistance and higher levels of glucanase activity than less acetylated chitosan. Similarly, when treatments were applied as seeds coating before planting, about 46% of plant protection was obtained using chitosan hydrolysate. It was concluded that, while less acetylated and degraded chitosan are better for direct inhibition of pathogen growth, partially acetylated and degraded chitosan are suitable to protect tobacco against P. parasitica by systemic induction of plant resistance.