Preparation and properties of chitosan–soybean trypsin inhibitor blend film with anti-Aspergillus flavus activity

The chitosan-based blend films were prepared from chitosan, soybean trypsin inhibitor extract (STI)/wild soybean trypsin inhibitor extract (WTI) and glycerol (Gly) solutions, the properties of which were also investigated, including thickness, mechanical property, water vapor transmission, optical transmittance, and solubility. In addition, the resulting films were characterized by scanning electron microscope (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The result of SEM images showed the surface and cross-section of chitosan–STI/WTI–Gly blend film had more smooth and dense morphology than pure chitosan film, which suggested there was a better compatibility among the three components. XRD and FTIR spectra indicated that the possible interaction force among the components might be the hydrogen bonds of NH?OC and OH?OC. Furthermore, the antifungal activity against A. flavus by the prepared blend films had been investigated. The facts that the germination and growth of A. flavus were strongly inhibited by chitosan–STI/WTI–Gly film indicated the blend films might be useful as potential bio-control packaging against A. flavus during the peanuts and other cereals storage.     

Chitosan–starch composite film: preparation and characterization

Chitosan film has potential applications in agriculture, food, and pharmacy. However, films made only from chitosan lack water resistance and have poor mechanical properties. Forming miscible, biodegradable composite film from chitosan with other hydrophilic biopolymers is an alternative. The objective of this study was to prepare chitosan/starch composite films by combining chitosan (deacetylated degree, 90%) solution and two thermally gelatinized cornstarches (waxy starch and regular starch with 25% amylose). The film’s tensile strength (TS), elongation-at-break (E), and water vapor transmission rate (WVTR) were investigated. The possible interactions between the two major components were evaluated by X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR). Regardless of starch type, both the TS and E of the composite films first increased and then decreased with starch addition. Composite film made with regular starch showed higher TS and E than those with waxy starch. The addition of starch decreased WVTRs of the composite films. The introduction of gelatinized starch suppressed the crystalline peaks of chitosan film. The amino group band of chitosan molecule in the FTIR spectrum shifted from 1578 cm⁻¹ in the chitosan film to 1584 cm⁻¹ in composite films. These results indicated that there was a molecular miscibility between these two components.     

Preparation of Cross-linked Chitosan Quaternary Ammonium Salt Hydrogel Films Loading Drug of Gentamicin Sulfate for Antibacterial Wound Dressing

Hydrogels, possessing high biocompatibility and adaptability to biological tissue, show great usability in medical applications. In this research, a series of novel cross-linked chitosan quaternary ammonium salt loading with gentamicin sulfate (CTMCSG) hydrogel films with different cross-linking degrees were successfully obtained by the reaction of chitosan quaternary ammonium salt (TMCS) and epichlorohydrin. Fourier transform infrared spectroscopy (FTIR), thermal analysis, and scanning electron microscope (SEM) were used to characterize the chemical structure and surface morphology of CTMCSG hydrogel films. The physicochemical property, gentamicin sulphate release behavior, cytotoxicity, and antibacterial activity of the CTMCSG against Escherichia coli and Staphylococcus aureus were determined. Experimental results demonstrated that CTMCSG hydrogel films exhibited good water stability, thermal stability, drug release capacity, as well as antibacterial property. The inhibition zone of CTMCSG hydrogel films against Escherichia coli and Staphylococcus aureus could be up to about 30 mm. Specifically, the increases in maximum decomposition temperature, mechanical property, water content, swelling degree, and a reduction in water vapor permeability of the hydrogel films were observed as the amount of the cross-linking agent increased. The results indicated that the CTMCSG-4 hydrogel film with an interesting physicochemical property, admirable antibacterial activity, and slight cytotoxicity showed the potential value as excellent antibacterial wound dressing.     

Antimicrobial fibers based on chitosan and polyvinyl-alcohol

A series of antimicrobial fibers with different weight ratio of chitosan (CS) and polyvinyl alcohol (PVA) were fabricated via a primarily industrialized trail of wet-spinning method, and the morphology and structure of the resulting fibers were studied with the aid of scanning electron micrography (SEM), infrared spectroscopy (FTIR), and X-ray diffraction (XRD). The CP60 blend fiber (60 % chitosan content) was confirmed as the best optimal sample among the blend fibers owing to strong intermolecular hydrogen bonds between PVA and chitosan and showed the maximum mechanical, antistatic, moisture absorption/desorption properties. The CP60 also exhibited good antimicrobial effects against Escherichia coli and Staphylococcus aureus as the chitosan fiber and could be recommended as the alternative material for the wound dressing and the food packing.     

Synthesis,Characterization, and Antibacterial Activity of Cross-Linked Chitosan-Glutaraldehyde

This present study deals with synthesis, characterization and antibacterial activity of cross-linked chitosan-glutaraldehyde. Results from this study indicated that cross-linked chitosan-glutaraldehyde markedly inhibited the growth of antibiotic-resistant Burkholderia cepacia complex regardless of bacterial species and incubation time while bacterial growth was unaffected by solid chitosan. Furthermore, high temperature treated cross-linked chitosan-glutaraldehyde showed strong antibacterial activity against the selected strain 0901 although the inhibitory effects varied with different temperatures. In addition, physical-chemical and structural characterization revealed that the cross-linking of chitosan with glutaraldehyde resulted in a rougher surface morphology, a characteristic Fourier transform infrared (FTIR) band at 1559 cm⁻¹, a specific X-ray diffraction peak centered at 2θ = 15°, a lower contents of carbon, hydrogen and nitrogen, and a higher stability of glucose units compared to chitosan based on scanning electron microscopic observation, FTIR spectra, X-ray diffraction pattern, as well as elemental and thermo gravimetric analysis. Overall, this study indicated that cross-linked chitosan-glutaraldehyde is promising to be developed as a new antibacterial drug.     

Antibacterial blend films of cellulose and chitosan prepared from binary ionic liquid system

A new hybrid ionic liquids solvent, 1-allyl-3-methylimidazolium chloride (AMIMCl) and glycine hydrochloride (Gly·HCl) was utilized to dissolve chitosan and fabricate chitosan/cellulose (Cs/Ce) blend films with chitosan proportion varying from 2 to 35 wt.% through solution casting method. FTIR, XRD, TG, SEM and EA were used to evaluate the prepared composites. Besides, the mechanical property and antibacterial activity were also analyzed. The shifting of the characteristic peaks of -NH and C=O for chitosan, similar crystal pattern with low intensity diffraction peaks at 2θ of around 20°, superior thermal stability (increased T_onset) with chitosan ratio below 10 wt.% in the composites suggested that the interactions via hydrogen bonds formed between chitosan and cellulose. Besides, the elemental analysis showed that the actual N% contents from the chitosan in the blend films were roughly equivalent to the theoretical value though the inevitable residue of ionic liquids. Furthermore, the blends not only presented compact structure but also processed high bacterial reduction to E. coli and S. aureus at pH 6.3, which indicated that the Cs/Ce blend films prepared via the Gly·HCl/AMIMCl dissolution method were suitable for production of degradable antibacterial materials.     

Organic-inorganic hybrid of chitosan/poly (vinyl alcohol) containing yttrium(III) membrane for the removal of Cr(VI)

In this present study, an organic-inorganic hybrid membrane was prepared by embedding yttrium(III) into chitosan matrix for the removal of Cr(VI) from aqueous solutions. Several techniques, including fourier infrared spectrum (FTIR), scanning electron microscope (SEM), X-ray diffraction (XRD), and transmission electron microscope (TEM) are employed to characterize the properties of the membrane. The mechanical properties of the membrane were also examined. The chitosan/poly(vinyl alcohol) containing yttrium(III) (CY) membrane was experimentally used for the removal of Cr(VI) ions from aqueous solution under the optimized conditions. The results showed that the adsorption capacity for the removal of Cr(VI) ions was enhanced when yttrium(III) was introduced. The adsorption data from the experiment were fit well by Langmuir isotherm. Based on Langmuir model, q _m was calculated to be 38.48 mg g^?1. Kinetic study results indicated that the adsorption process followed a pseudo-second-order kinetics.     

Fabrication,Characterization and Antimicrobial property of natural TTOLs/CS composite sponges

The essential oil liposomes, a kind of ecological friendly natural antibacterial agents, have good bactericidal effect. In the present study, tea tree oil liposomes (TTOLs) were prepared by the thin-membrane hydration method with sonication, and then were blended with chitosan (CS) to successfully fabricate novel TTOLs/CS composite sponges by freeze-dried method. Through the scanning electron microscope (SEM), fourier transform infrared spectroscopy (FTIR) and performance tests, it was found that the material had good water absorption, water retention and water vapor permeability due to the high porosity. Furthermore, the incorporation of TTOLs in the CS-based sponges significantly improved the microbicidel effect of the sponges against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and Candida albicans (C. albicans). Killing log values of TTOLs/CS composite sponges against bacteria and fungi reached over 3. According to the microbial clearance test, propidium iodide (PI) fluorescence test and transmission electron microscope (TEM) observation, the results indicated on one hand that TTOLs/CS composite sponges adsorbed and intercepted microbial cells through the internal pore and surface charge, and on the other hand that they could destroy bacterial intercellular substance, disperse cell colony and damage the integrity of cell membrane, finally leading to the death of microbial cells. In summary, TTOLs/CS composite sponges had great potential to be used as antimicrobial materials in the field of food, cosmetics, medicine, biomedical and biochemical engineering.     

Effect of thermal annealing on mechanical properties of polyelectrolyte complex nanofiber membranes

Optimization of mechanical properties is required in the applications of tissue-engineered scaffolds. Thermal annealing strategy is proposed to improve the mechanical properties of polyelectrolyte complex nanofiber membranes. The effects of annealing on the structural and mechanical properties of electrospun chitosan-gelatin (CG) nanofiber membranes were investigated using tensile tests, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and differential scanning calorimetry (DSC). Tensile test results showed that annealing processing at 90 °C produced 1.3-fold and 1.1-fold increase on Young’s modulus and tensile strength, respectively. By scanning electron microscopy (SEM) observation, it was found there was a formation of partial interfiber bonding when annealing temperature was elevated over the glass transition temperature (T _g ) of CG nanofibers. FTIR results showed enhanced molecular interactions within fibers, suggesting that annealing treatment promoted the conjunction between chitosan and gelatin. In contrast, no detectable changes in crystallinity for CG nanofiber specimens were exhibited on XRD patterns following annealing treatment. In addition, thermal annealing induced the improvement in thermal stability, aqueous stability and swelling capacity. Therefore, annealing is proved to be an effective strategy for mechanical enhancement of polyelectrolyte complex nanofibrous scaffolds. The enhanced stiffness and strength is mainly attributed to the formation of interfiber bonding and strengthened molecular interactions between chitosan and gelatin.     

Manufacture and performance of O-carboxymethyl chitosan sodium salt/cellulose fibers in N-methylmorpholine-N-oxide system

A series of O-carboxymethyl chitosan sodium salt (NaCMCh) with different degree of substitution (DS) of -CH₂COONa agent were successfully prepared by altering the reaction temperature and time. Both fourier transform infrared spectroscopy (FTIR) and ¹³C-Nuclear Magnetic Resonance (¹³C-NMR) were used to study the structure of NaCMCh. And the impact of DS on the antibacterial activity of NaCMCh was investigated. Then, the NaCMCh with optimal antibacterial activity was selected to prepare NaCMCh/cellulose fibers in N-methylmorpholine-N-oxide (NMMO) system. The structure, crystallization behavior, thermal property and morphology of obtained fibers were carefully studied with FTIR, Wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), thermal gravimetric (TG) and scanning electron microscope (SEM), respectively. Meanwhile, the antibacterial activity as well as mechanical properties of resultant fibers was also investigated. The results demonstrated that the fibers had strong antibacterial activity against Escherichia coli (E. coli), acceptable mechanical properties and good water retention.     

Dissolution and regeneration behavior of chitosan in 3-methyl-1-(ethylacetyl)imidazolium chloride

3-methyl-1-(ethylacetyl)imidazolium chloride ([EtMIM]Cl), was synthesized for chitosan dissolution, and the dissolution and regeneration behaviors of chitosan in [EtMIM]Cl were thoroughly investigated. The solubility of chitosan in [EtMIM]Cl was measured at temperatures ranging from 40 °C to 110 °C, based on which the thermodynamic parameters of chitosan in [EtMIM]Cl were calculated. The polarizability and hydrogen bond accepting ability was determined by solvatochromic UV/vis spectroscopy. The regenerated chitosan from [EtMIM]Cl by adding methanol was characterized by thermogravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Density functional theory (DFT) computations were performed to study the interactions between [EtMIM]Cl and chitobiose. Five kinds of hydrogen bonds, C-H/O, O-H/O, O-H/Cl, C-H/Cl, N-H/Cl were found, suggesting strong interactions between [EtMIM]Cl and chitobiose. In particular, the oxygen atom and the active methylene group of carboxylic ester in [EtMIM]⁺, formed strong hydrogen bonding with chitobiose. The molecular simulation results indicated that both the Cl^? anions and [EtMIM]⁺ cation played important roles in the chitosan dissolution process, by the disruption of native hydrogen bonds of chitosan.     

Antimicrobial properties of chitosan nanoparticles: Mode of action and factors affecting activity

The present investigation describes the synthesis and characterization of novel biodegradable nanoparticles based on chitosan for biomedical applications. The presence of primary amine groups in repeating units of chitosan grants it several properties like antibacterial activity, antitumor activity and so on. Chitosan forms nanoparticles spontaneously on the addition of polyanion tripolyphosphate which has greater antimicrobial activity than parent chitosan. In the present study, chitosan nanoparticles (ChNP) were prepared by the ionic gelation method. The physiochemical characteristics of nanoparticles were analyzed using XRD, SEM, FTIR. The antibacterial activity of chitosan nanoparticles against medical pathogens Klebsiella pneumoniae, Escherichia coli, Staphylococcus aureus and Pseudomonas aeruginosa was evaluated by calculation of minimum inhibitory concentration (MIC) and compared with chitosan and chitin activity. The mode of action and factors affecting antibacterial activity were also analyzed. ChNP compounds exhibited superior antimicrobial activity against all microorganisms in comparison with chitosan and chitin. The antibiofilm activity was studied using crystal violet assay and growth on congo red agar. The study is thus a good demonstration of the applicability of chitosan nanoparticles as an effective antimicrobial agent with antibiofilm activity as well.     

Enhancing Stability and Mucoadhesive Properties of Chitosan Nanoparticles by Surface Modification with Sodium Alginate and Polyethylene Glycol for Potential Oral Mucosa Vaccine Delivery

Background: The present study aimed to fabricate surface-modified chitosan nanoparticles with two mucoadhesive polymers (sodium alginate and polyethylene glycol) to optimize their protein encapsulation efficiency, improve their mucoadhesion properties, and increase their stability in biological fluids. Method: Ionotropic gelation was employed to formulate chitosan nanoparticles and surface modification was performed at five different concentrations (0.05, 0.1, 0.2, 0.3, 0.4% w/v) of sodium alginate (ALG) and polyethylene glycol (PEG), with ovalbumin (OVA) used as a model protein antigen. The functional characteristics were examined by dynamic light scattering (DLS), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM)/scanning transmission electron microscopy (STEM). Stability was examined in the presence of simulated gastric and intestinal fluids, while mucoadhesive properties were evaluated by in vitro mucin binding and ex vivo adhesion on pig oral mucosa tissue. The impact of the formulation and dissolution process on the OVA structure was investigated by sodium dodecyl-polyacrylamide gel electrophoresis (SDS-PAGE) and circular dichroism (CD). Results: The nanoparticles showed a uniform spherical morphology with a maximum protein encapsulation efficiency of 81%, size after OVA loading of between 200 and 400 nm and zeta potential from 10 to 29 mV. An in vitro drug release study suggested successful nanoparticle surface modification by ALG and PEG, showing gastric fluid stability (4 h) and a 96 h sustained OVA release in intestinal fluid, with the nanoparticles maintaining their conformational stability (SDS-PAGE and CD analyses) after release in the intestinal fluid. An in vitro mucin binding study indicated a significant increase in mucin binding from 41 to 63% in ALG-modified nanoparticles and a 27–49% increase in PEG-modified nanoparticles. The ex vivo mucoadhesion showed that the powdered particles adhered to the pig oral mucosa. Conclusion: The ALG and PEG surface modification of chitosan nanoparticles improved the particle stability in both simulated gastric and intestinal fluids and improved the mucoadhesive properties, therefore constituting a potential nanocarrier platform for mucosal protein vaccine delivery.     

Development and evaluation of novel eucalyptus essential oil liposomes/chitosan composite sponges for medical use

Novel eucalyptus essential oil liposomes (EEOLs)/chitosan composite sponges (EC) were successfully fabricated by electrostatic self-assembly. EEOLs were prepared by the thin-membrane hydration method with sonication and blended with chitosan solution to create the sponges by lyophilization. The observations of transmission electron microscopy (TEM) and scanning electron microscopy (SEM) confirmed the existence of eucalyptus essential oil in the lipid bilayer of liposomal membrane and the location of the liposomes in positive holes formed by the protonated amino groups of chitosan. The average size of EEOLs was about 60 nm. Fourier transform infrared (FTIR) analysis showed the destroy of inter- and intramolecular hydrogen bonding among chitosan chains and the construction of the intermolecular hydrogen bonding between chitosan and molecules on the surface of EEOLs. The incorporation of EEOLs in chitosan sponges slightly decreased the porosity, fluid absorptivity, gas permeability and hemostatic property of sponges, but increased their biodegradation ability. EC exhibited more rapid and efficient microbicidal effects against Staphylococcus aureus (S. aureus), Pseudomonas aeruginosa (P. aeruginosa) and Candida albicans (C. albicans) than pure chitosan sponges. EC showed no toxicity toward human HEK293T cells and no significant adverse effect on cell attachment and proliferation of HEK293T cells. This inherent behaviour can be exploited to apply in the medical field.     

Oceanalin B,a Hybrid α,ω-Bifunctionalized Sphingoid Tetrahydroisoquinoline β-Glycoside from the Marine Sponge Oceanapia sp.

Oceanalin B (1), an α,ω-bipolar natural product belonging to a rare family of sphingoid tetrahydoisoquinoline β-glycosides, was isolated from the EtOH extract of the lyophilized marine sponge Oceanapia sp. as the second member of the series after oceanalin A (2) from the same animal. The compounds are of particular interest due to their biogenetically unexpected structures as well as their biological activities. The structure and absolute stereochemistry of 1 as a α,ω-bifunctionalized sphingoid tetrahydroisoquinoline β-glycoside was elucidated using NMR, CD and MS spectral analysis and chemical degradation. Oceanalin B exhibited in vitro antifungal activity against Candida glabrata with a MIC of 25 μg/mL.     

Antifungal activity of leaf extracts from South African trees against plant pathogens

The antifungal activity of acetone, methanol, hexane and dichloromethane leaf extracts of six plant species (Bucida buceras, Breonadia salicina, Harpephyllum caffrum, Olinia ventosa, Vangueria infausta and Xylotheca kraussiana) were evaluated for antifungal activity against seven plant pathogenic fungal species (Aspergillus niger, Aspergillus parasiticus, Colletotricum gloeosporioides, Penicillium janthinellum, Penicillium expansum, Trichoderma harzianum and Fusarium oxysporum). These plant species were selected from 600 evaluated inter alia, against two animal fungal pathogens. All plant extracts were active against the selected plant pathogenic fungi. Of the six plant species, B. buceras had the best antifungal activity against four of the fungi, with minimum inhibitory concentration (MIC) values as low as 0.02 mg/ml and 0.08 mg/ml against P. expansum, P. janthinellum, T. harzianum and F. oxysporum. Some of the plant extracts had moderate to low activity against other fungi, indicating that the activity is not based on a general metabolic toxicity. P. janthinellum, T. harzianum and F. oxysporum were the most sensitive fungal species, with a mean MIC of 0.28 mg/ml, while the remaining four fungi were more resistant to the extracts tested, with mean MICs above 1 mg/ml. The number of active compounds in the plant extracts was determined using bioautography with the listed plant pathogens. No active compounds were observed in some plant extracts with good antifungal activity as a mixture against the fungal plant pathogens, indicating possible synergism between the separated metabolites, B. salicina and O. ventosa were the most promising plant species, with at least three antifungal compounds. Leaf extracts of different plant species using different methods (acetone, hexane, DCM and methanol) had antifungal compounds with the same R_f values. The same compounds may be responsible for activity in extracts of different plant species. Based on the antifungal activity, crude plant extracts may be a cost effective way of protecting crops against fungal pathogens. Because plant extracts contain several antifungal compounds, the development of resistant pathogens may be delayed.     

Antifungal activity of polyacetylenes isolated from Cirsium japonicum roots against various phytopathogenic fungi

Antifungal substances from a methanol extract of Cirsium japonicum roots were purified and characterized, and their antifungal activities against various plant pathogens were evaluated. Three polyacetylene substances were isolated from roots of C. japonicum using repeated column chromatography; these were identified as ciryneol A, ciryneol C and 1-heptadecene-11,13-diyne-8,9,10-triol by mass and nuclear magnetic resonance spectral analyses. In vitro antifungal activity of the three substances varied according to compound and target species. Magnaporthe oryzae, Colletotrichum coccodes, Colletotrichum acutatum, Pythium ultimum and Botrytis cinerea were relatively sensitive to the three polyacetylenes, with IC₅₀ values below 50 μg mL⁻¹. In vivo, they all showed similar and broad antifungal spectra against the seven plant diseases tested. At 500 μg mL⁻¹, all three compounds effectively suppressed the development of rice blast, rice sheath blight, tomato late blight, wheat leaf rust and red pepper anthracnose, with control values over 90%. They were highly active especially against wheat leaf rust; they controlled the development of this disease more than 88% even at a concentration of 125 μg mL⁻¹. In addition, ciryneol C effectively suppressed barley powdery mildew. This is the first report on the antifungal activities of the three polyacetylenes from roots of C. japonicum against plant pathogenic fungi. Polyacetylenes from roots of C. japonicum may contribute to the development of environmentally safer alternatives to protect crops from various phytopathogenic fungi.     

Antifungal activity of prenylated flavonoids isolated from Tephrosia apollinea L. against four phytopathogenic fungi

Four prenylated flavonoids, isoglabratephrin, (+)-glabratephrin, tephroapollin-F and lanceolatin-A were isolated from Tephrosia apollinea L. growing in Egypt. The structures of compounds have been elucidated using physical and spectroscopic methods including (UV, IR, ¹H NMR, ¹³C NMR, DEPT, 2D ¹H–¹H COSY, HSQC, HMBC and NOESY). The isolated flavonoids showed considerable antifungal activity against four phytopathogenic fungi, namely Alternaria alternata, Helminthosporium sp., Colletotrichum acutatum and Pestalotiopsis sp. in a dose-dependent manner using the agar well-diffusion bioassay. They differ significantly in their activity with tephroapollin-F was the most effective. In a test using a concentration of 4 mg/ml of tephroapollin-F, strong fungicidal activities (32.8–58.3%) were produced against the test fungi, where C. acutatum, Helminthosporium sp. and Pestalotiopsis sp. showed greater susceptibility, while A. alternata was the least susceptible. Using the same concentration, the two flavonoids isoglabratephrin and (+)-glabratephrin showed moderate activities with % inhibition of fungal growth were ranged between (16.1–37.8) against A. alternata, Helminthosporium sp. and Pestalotiopsis sp., while showed a strong antifungal activity against C. acutatum (% growth inhibition were 46.4 and 42.9, respectively). In all treatments, the flavonoid lanceolatin-A exhibited weak to moderate activities. Using lower concentrations of the test flavonoids (2 and 1 mg/ml), weak to moderate antifungal activities were observed against all of the test fungal strains. In all cases and regardless of the flavonoid tested, C. acutatum was the most susceptible, while A. alternata was the least. The study recommends the use of the test compounds as rational fungicides of natural origin.     

Five New Cytotoxic Metabolites from the Marine Fungus Neosartorya pseudofischeri

The marine fungus Neosartorya pseudofischeri was isolated from Acanthaster planci from the South China Sea. In a preliminary bioactivity screening, the crude methanol extract of the fungal mycelia showed significant inhibitory activity against the Sf9 cell line from the fall armyworm Spodoptera frugiperda. Five novel compounds, including 5-olefin phenylpyropene A (1), 13-dehydroxylpyripyropene A (4), deacetylsesquiterpene (7), 5-formyl-6-hydroxy-8-isopropyl-2- naphthoic acid (9) and 6,8-dihydroxy-3-((1E,3E)-penta-1,3-dien-1-yl)isochroman-1-one (10), together with eleven known compounds, phenylpyropene A (2) and C (3), pyripyropene A (5), 7-deacetylpyripyropene A (6), (1S,2R,4aR,5R,8R,8aR)-1,8a-dihydroxy-2-acetoxy-3,8-dimethyl-5- (prop-1-en-2-yl)-1,2,4a, 5,6,7,8,8a-octahydronaphthalene (8), isochaetominine C (11), trichodermamide A (12), indolyl-3-acetic acid methyl ester (13), 1-acetyl-β-carboline (14), 1,2,3,4-tetrahydro-6-hydroxyl-2-methyl-l,3,4-trioxopyrazino[l,2-a]-indole (15) and fumiquinazoline F (16), were obtained. The structures of these compounds were determined mainly by MS and NMR data. The absolute configuration of 9 was assigned by the single-crystal X-ray diffraction studies. Compounds 1–11 and 15 showed significant cytotoxicity against the Sf9 cells from S. frugiperda.     

Chitosan boehmite-alumina nanocomposite films and thyme oil vapour control brown rot in peaches (Prunus persica L.) during postharvest storage

Brown rot (Monilinia spp.) affects the shelf life, fruit quality and marketability of peaches (Prunus persica L.). Increasing consumer concern regarding food safety makes it necessary to search for natural environmentally friendly alternative products for postharvest disease control. In this investigation, polyethylene terephthalate (PET) punnets containing thyme oil (TO sachets) and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the incidence and severity of brown rot caused by Monilinia laxa in artificially inoculated peach fruits (cv. Kakawa) held at 25 °C for 5 days. Furthermore, PET punnets containing TO sachets and sealed with chitosan/boehmite nanocomposite lidding films significantly reduced the brown rot incidence to 10% in naturally infected fruits stored at 0.5 °C, 90% RH for 7 days and at the simulated market shelf conditions for 3 days at 15 °C, 75% RH. The chitosan/boehmite nanocomposite lidding films maintained the active components of thyme oil, thymol (56.43% RA), caryophyllen (9.47% RA) and β-linalool (37.6% RA) within the (head space volatiles) punnet. Panellists preferred fruits packed from commercial punnet containing thyme oil (sachets) and sealed with chitosan/boehmite nanocomposite lidding films due to overall appearance, taste, and natural peach flavour.