Antibacterial activity and mechanism of chloroform fraction from aqueous extract of mugwort leaves (Artemisia argyi L.) against Staphylococcus aureus

In this work, the antibacterial activity and mechanism of chloroform fraction obtained from aqueous extract of mugwort leaves against Staphylococcus aureus were investigated. The extract showed obvious antibacterial activity against S. aureus which the minimum inhibitory concentration and minimum bactericidal concentration were determined to be 3·0 and 6·0 mg ml⁻¹ respectively. The mechanism study suggested that the extract could destroy the integrity of the S. aureus cell walls and increase the permeability of cell membrane in a certain concentration, but it could not kill S. aureus in a short time. Instead, the extract could make bacteria in a state of apoptosis for a long time, interfere with the normal physiological metabolism of bacteria, and eventually make bacteria die, which was confirm by scanning electronic microscope.     

Antibacterial Potential of Garlic-Derived Allicin and Its Cancellation by Sulfhydryl Compounds

Allicin (allyl 2-propenethiosulfinate), an antibacterial principle of garlic, has drawn much attention, since it has potent antimicrobial activity against a range of microorganisms, including methicillin-resistant Staphylococcus aureus. There have been many reports on the antibacterial properties of allicin, but no quantitative comparison of antibacterial activities between freshly prepared garlic extract and clinically useful antibiotics has been performed. To verify the substantial antibacterial effect of aqueous garlic extract, we compared it with those of allicin and several clinically useful antibiotics using two representative bacteria commonly found in the human environment, Gram-positive S. aureus and Gram-negative Escherichia coli. The garlic extract had more potent anti-staphylococcal activity than an equal amount of allicin. In terms of antibiotic potency against Gram-positive and Gram-negative bacteria, authentic allicin had roughly 1–2% of the potency of streptomycin (vs. S. aureus), 8% of that of vancomycin (vs. S. aureus), and only 0.2% of that of colistin (vs. E. coli). The antibacterial activity of allicin was completely abolished by cysteine, glutathione and coenzyme A, but not by non-SH-compounds. The oxygen in the structure (–S(=O)–S–) of allicin therefore functions to liberate the S-allyl moiety, which might be an offensive tool against bacteria.     

In vitro evaluation of Datura innoxia (thorn-apple) for potential antibacterial activity

Various parts of Datura innoxia were examined for potential antibacterial activity by preparing their crude aqueous and organic extracts against Gram-negative bacteria (Escherichia coli and Salmonella typhi) and Gram-positive bacteria (Bacillus cereus, Bacillus subtilis and Staphylococcus aureus). The results of agar well diffusion assay indicated that the pattern of inhibition depends largely upon the plant part, solvent used for extraction and the organism tested. Extracts prepared from leaves were shown to have better efficacy than stem and root extracts. Organic extracts provided potent antibacterial activity as compared to aqueous extracts. Among all the extracts, methanolic extract was found most active against almost all the bacterial species tested. Gram-positive bacteria were found most sensitive as compared to Gram-negative bacteria. Staphylococcus aureus was signifi cantly inhibited by almost all the extracts even at very low MIC followed by other Gram-positives. For Escherichia coli (a Gram-negative bacterium), the end point was not reached for ethyl acetate extract while it was very high for other extracts. The study promises an interesting future for designing a potentially active antibacterial agent from Datura innoxia.     

Design,synthesis and antistaphylococcal activity of marine pyrrole alkaloid derivatives

Abstract

A novel set of 16 hybrids of bromopyrrole alkaloids with aroyl hydrazone were designed, synthesized and evaluated for antibacterial and antibiofilm activities against methicillin-resistant Staphylococcus aureus (MRSA; ATCC 43866), methicillin-susceptible Staphylococcus aureus (MSSA; ATCC 35556) and Staphylococcus epidermidis (SE, S. epidermidis ATCC 35984). Of the 16 tested hybrids, 14 exhibited equal or superior antibiofilm activity against MSSA and MRSA relative to standard vancomycin. Compound 4m showed highest potency with antibiofilm activity of 0.39?µg/mL and 0.78?µg/mL against MSSA and MRSA, respectively. Thus, this compound could act as a potential lead for further development of new antistaphylococcal drugs.     

Extracellular biosynthesis,characterization, optimization of silver nanoparticles (AgNPs) using Bacillus mojavensis BTCB15 and its antimicrobial activity against multidrug resistant pathogens

Abstract

Biosynthesis of metal nanoparticles is an area of interest among researchers because of its eco-friendly approach. Current study focuses at biosynthesis of silver nanoparticles (AgNPs) and optimization of physico-chemical conditions to obtain mono-dispersed and stable AgNPs having antimicrobial activity. Initially Bacillus mojavensis BTCB15 produced silver nanoparticles (AgNPs) of 105?nm. Silver nanoparticles (AgNPs) were characterized by particle size analyzer, UV-Vis Spectroscopy, Fourier transforms infrared spectroscopy (FTIR), Atomic force microscopy (AFM), and X-ray diffraction (XRD). Whereas, under optimal conditions of temperature 55?°C, pH 8, addition of surfactant Tween 20, and metal ion K₂SO₄, about 104% size reduction was achieved with average size of 2.3nm. Molecular characterization revealed 98% sequence homology with Bacillus mojavensis. AgNPs exhibited antibacterial activity at concentrations ranging from 0.5 to 2.5?µg/µl against Escherichia coli BTCB03, Klebsiella pneumonia BTCB04, Acinetobacter sp. BTCB05, and Pseudomonas aeruginosa BTCB01 but none against Staphylococcus aureus BTCB02. Highest antibacterial activity was observed at 0.27?µg/µl and lowest at 0.05?µg/µl of AgNPs indicated by zone of inhibition. Conclusively, under optimum conditions, Bacillus mojavensis BTCB15 was able to produce AgNPs of 2.3?nm size and had antibacterial activity against multi drug resistant pathogens.     

In vitro antibacterial activity and physicochemical properties of a crude methanol extract of the larvae of the blow fly Lucilia cuprina

The emergence of multidrug‐resistant bacterial strains has prompted the reintroduction of maggot therapy in the treatment of chronic, infected wounds. Many previous studies have demonstrated the potent antibacterial activity of larval excretions/secretions of the blowfly Lucilia sericata (Meigen) (Diptera:Calliphoridae) against bacteria. However, the antibacterial activity of its sibling species, Lucilia cuprina (Wiedemann) (Diptera:Calliphoridae) against a wide range of pathogenic bacteria has never been determined. The aim of this study was to develop a new procedure to produce whole body extract of larvae of L. cuprina via methanol extraction as well as to demonstrate the in vitro antibacterial activity of this extract against seven selected wound pathogens (Staphylococcus aureus, methicillin‐resistant S. aureus, S. epidermidis, Streptococcus pyogenes, Klebsiella pneumoniae, Pseudomonas aeruginosa and Escherichia coli). The turbidimetric assay demonstrated that L. cuprina larval extract was significantly potent against all bacteria tested (P < 0.001). Additionally, colony‐forming unit (CFU), agar well diffusion and minimum inhibitory concentration assays have confirmed the apparent potency of larval extract against P. aeruginosa. The reconstituted larval extract was highly robust and thermally stable. These observations substantiated the feasibility of the methanol extraction method in the production of larval extract.     

Characterization of clinical strains of MSSA,MRSA and MRSE isolated from skin and soft tissue infections and the antibacterial activity of ZnO nanoparticles

Staphylococcus aureus, particularly methicillin-resistant S. aureus (MRSA), is an important cause of pyogenic skin and soft tissue infections (SSTIs). MRSA is an important pathogen in the healthcare sector that has neither been eliminated from the hospital nor community environment. In humans, S. aureus causes superficial lesions in the skin and localized abscesses, pyogenic meningitis/encephalitis, osteomyelitis, septic arthritis, invasive endocarditis, pneumonia, urinary tract infections and septicemia. Investigations focused in the search of other alternatives for the treatment of MRSA infections are in progress. Among the range of compounds whose bactericidal activity is being investigated, ZnO nanoparticles (ZnO–NPs) appears most promising new unconventional antibacterial agent that could be helpful to confront this and other drug-resistant bacteria. The aim of present study is to investigate the antibacterial potential of ZnO–NPs against Staphylococcus species isolated from the pus and wounds swab from the patients with skin and soft tissue infections in a tertiary care hospital of north India. ZnO–NPs (≈19.82 nm) synthesized by sol–gel process were characterized using scanning electron microscopy, X-ray diffraction , and Atomic force microscopy. The antibacterial potential was assessed using time-dependent growth inhibition assay, well diffusion test, MIC and MBC test and colony forming units methods. ZnO–NPs inhibited bacterial growth of methicillin-sensitive S. aureus (MSSA), MRSA and methicillin-resistant S. epidermidis (MRSE) strains and were effective bactericidal agents that were not affected by drug-resistant mechanisms of MRSA and MRSE.     

利用Mariannaea sp.HJ菌株胞内提取物合成纳米银及其抗菌特性研究

【目的】近年来,纳米银由于其自身独特的抗菌活性而受到越来越多的关注,有研究表明纳米银是一种广谱的抗菌剂,其对数十种致病微生物都有强烈的抑制和杀灭作用。相较于传统的合成方法而言,具有反应条件温和、环境友好等优势的生物合成法是目前的研究热点。【方法】本研究利用真菌Mariannaea sp. HJ的胞内提取物合成纳米银,并对其合成条件进行优化调控,还进一步考察了合成的纳米银颗粒的抗菌性能。【结果】胞内提取物浓度350 mg/L、AgNO_3浓度5 mmol/L、pH 7.0为菌株HJ胞内提取物合成纳米银的最优条件;TEM图像表明合成的纳米银颗粒主要为球形和伪球形,分散性良好,无明显的团聚现象;XRD表明合成的纳米银晶体结构为面心立方体结构;通过FTIR分析结果推测提取物中的羟基、羧基等官能团可能参与了纳米银的还原和稳定过程。此外,在本实验条件下合成的纳米银颗粒对革兰氏阴性菌Escherichia coli BL21和革兰氏阳性菌Arthrobacter sp. W1都有较好的抗菌活性。【结论】真菌Mariannaea sp. HJ胞内提取物能合成尺寸均一且分散性良好的球形纳米银颗粒,合成的纳米银颗粒在抗菌方面具有潜在的研究价值。     

Pomegranate peel induced biogenic synthesis of silver nanoparticles and their multifaceted potential against intracellular pathogen and cancer

In the field of nano-biotechnology, silver nanoparticles (AgNPs) share a status of high repute owing to their remarkable medicinal values. Biological synthesis of environment-friendly AgNPs using plant extracts has emerged as the beneficial alternative approach to chemical synthesis. In the current study, we have synthesized biogenic silver nanoparticles (PG-AgNPs) using the peel extract of Punica granatum as a reducing and stabilizing agent. The as-synthesized PG-AgNPs were characterized and evaluated for their antibacterial and anticancer potential. UV–Visible spectroscopy, transmission electron microscopy (TEM) and dynamic light scattering (DLS) confirmed the formation of biogenic PG-AgNPs. The antibacterial potential was assessed against the biofilm of Listeria monocytogenes. The PG-AgNPs were efficacious against sessile bacteria and their biofilm as well. The as-synthesized nanoparticles at sub-MIC values showed dose-dependent inhibition of biofilm formation. Corroborating results were observed under crystal violet assay, Congo red staining, Confocal microscopy and SEM analysis. The anticancer ability of the nanoparticles was evaluated against MDA-MB-231 metastatic breast cancer cells. As evident from the MTT results, PG-AgNPs significantly reduced the cell viability in a dose-dependent manner. Exposure of MDA-MB-231 cells led to the accumulation of reactive oxygen species (ROS). Morphological changes and DNA fragmentation showed the strong positive effect of PG-AgNPs on the induction of apoptosis. Collectively, the as-synthesized PG-AgNPs evolved with synergistically emerged attributes that were effective against L. monocytogenes and also inhibited its biofilm formation; moreover, the system displayed lower cytotoxic manifestation towards mammalian cells. In addition, the PG-AgNPs embodies intriguing anticancer potential against metastatic breast cancer cells.     

Synthesis and comparative study on the antimicrobial activity of hybrid materials based on silver nanoparticles (AgNps) stabilized by polyvinylpyrrolidone (PVP)

Hybrid materials based on polyvinylpyrrolidone (PVP) with silver nanoparticles (AgNps) were synthesized applying two different strategies based on thermal or chemical reduction of silver ions to silver nanoparticles using PVP as a stabilizer. The formation of spherical silver nanoparticles with diameter ranging from 9 to 16 nm was confirmed by TEM analysis. UV-vis and FTIR spectroscopy were also applied to confirm the successful formation of AgNps. The antibacterial activity of the synthesized AgNPs/PVP against etalon strains of three different groups of bacteria—Staphylococcus aureus (S. aureus; gram-positive bacteria), Escherichia coli (E. coli; gram-negative bacteria), Pseudomonas aeruginosa (P. aeruginosa; non-ferment gram-negative bacteria), as well as against spores of Bacillus subtilis (B. subtilis) was studied. AgNps/PVP were tested for the presence of fungicidal activity against different yeasts and mold such as Candida albicans, Candida krusei, Candida tropicalis, Candida glabrata, and Aspergillus brasiliensis. The hybrid materials showed a strong antimicrobial effect against the tested bacterial and fungal strains and therefore have potential applications in biotechnology and biomedical science.     

Ailanthus altissima leaf extract mediated green production of zinc oxide (ZnO) nanoparticles for antibacterial and antioxidant activity

BackgroundFabricating zinc oxide nanoparticles (ZnO-NPs) from plant extracts is a cost-effective, safe, and environmentally friendly alternative to established chemical procedures. This study was aimed at the environmentally friendly fabrication of ZnO-NPs from plant extract. An additional objective was to investigate the antibacterial and antioxidant activity of these biosynthesized ZnO-NPs.MethodsZnO-NPs were fabricated using the leaf extract of Ailanthus altissima, as an eco-friendly approach. The physicochemical properties of ZnO-NPs were explored using UV–visible spectroscopy, scanning electron microscopy, X-ray diffraction, and Fourier transform infrared spectrometry. The bio-fabricated ZnO-NPs were examined for bactericidal activity against pathogenic bacteria (gram-negative and gram-positive) using the agar well diffusion technique. The antioxidant efficiency of ZnO-NPs was assessed using a DPPH assay.ResultsA surface Plasmon peak was recorded at 327 nm, showing the existence of ZnO-NPs in the reaction solution of plant extract and zinc sulfate hexahydrate salt. These nanoparticles were predominantly spherical and capped by different functional groups of biomolecules. Furthermore, ZnO-NPs showed a dose-dependent antibacterial and antioxidant activity. At 20 mg/mL ZnO-NPs, the maximum bactericidal potential of ZnO-NPs was reported against Staphylococcus aureus (201.2 mm). ZnO-NPs have an IC₅₀ value of 78.23 µg/mL, indicating that they are an effective antioxidant.ConclusionThis research presents an environmentally acceptable method for producing spherical ZnO-NPs with high antibacterial and antioxidant activities. These bio-fabricated ZnO-NPs could be a good option for applications in medicine and the healthcare industry.     

Antibacterial activity of<Emphasis Type="Italic">Ulva lactuca</Emphasis> against methicillin-resistant<Emphasis Type="Italic">Staphylococcus aureus</Emphasis> (MRSA)

Thein vitro antimicrobial activity of the marine green algaeUlva lactuca was examined against gram-positive bacteria, gram-negative bacteria, and a fungus. The ethyl-ether extract of algae exhibited a broad-spectrum of antibacterial activity. but not antifungal activity againstCandida albicans. In particular, theU. lactuca extract showed strong activity aganst the bacterium methicillin-resistantStaphylococcus aureus (MRSA). This result confirms the potential use of seaweed extracts as a source of antibacterial compounds or as a health-promoting food for aquaculture.     

Synthesis,molecular docking,binding free energy calculation and molecular dynamics simulation studies of benzothiazol-2-ylcarbamodithioates as Staphylococcus aureus MurD inhibitors

Abstract

A new series of benzothiazol-2-ylcarbamodithioate functional compounds 5a-f has been designed, synthesized and characterized by spectral data. These compounds were screened for their in vitro antibacterial activity against strains of Staphylococcus aureus (NCIM 5021, NCIM 5022 and methicillin-resistant isolate 43300), Bacillus subtilis (NCIM 2545), Escherichia coli (NCIM 2567), Klebsiella pneumoniae (NCIM 2706) and Psudomonas aeruginosa (NCIM 2036). Compounds 5a and 5d exhibited significant activity against all the tested bacterial strains. Specifically, compounds 5a and 5d showed potent activity against K. pneumoniae (NCIM 2706), while compound 5a also displayed potent activity against S. aureus (NCIM 5021). Compound 5d showed minimum IC₅₀ value of 13.37?μM against S. aureus MurD enzyme. Further, the binding interactions of compounds 5a-f in the catalytic pocket have been investigated using the extra-precision molecular docking and binding free energy calculation by MM-GBSA approach. A 30?ns molecular dynamics simulation of 5d/modeled S. aureus MurD enzyme was performed to determine the stability of the predicted binding conformation.     

Linoleic acid, α-linolenic acid,and monolinolenins as antibacterial substances in the heat-processed soybean fermented with Rhizopus oligosporus

ABSTRACT

Antibacterial activities against Staphylococcus aureus and Bacillus subtilis were found in an ethanol fraction of tempe, an Indonesian fermented soybean produced using Rhizopus oligosporus. The ethanol fraction contained free fatty acids, monoglycerides, and fatty acid ethyl esters. Among these substances, linoleic acid and α-linolenic acid exhibited antibacterial activities against S. aureus and B. subtilis, whereas 1-monolinolenin and 2-monolinolenin exhibited antibacterial activity against B. subtilis. The other free fatty acids, 1-monoolein, monolinoleins, ethyl linoleate, and ethyl linolenate did not exhibit bactericidal activities. These results revealed that R. oligosporus produced the long-chain polyunsaturated fatty acids and monolinolenins as antibacterial substances against the Gram-positive bacteria during the fungal growth and fermentation of heat-processed soybean.     

Inhibition of methicillin-resistant Staphylococcus aureus (MRSA) biofilm by cationic poly (D,L-lactide-co-glycolide) nanoparticles

Abstract

The emergent need for new treatment methods for multi-drug resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) has focused attention on novel potential tools like nanoparticles (NPs). In the present study, a drug-free cationic nanoparticles (CNPs) system was developed and its anti-MRSA effects were firstly investigated. The results showed that CNPs (261.7?nm, 26.1?mv) showed time- and concentration-dependent activity against MRSA growth, killing ～ 90% of planktonic bacterial cells in 3?h at 400?μg ml^?1, and completely inhibiting biofilm formation at 1000?μg ml^?1. Moreover, CNPs at 400?μg ml^?1 reduced the minimum inhibitory concentration (MIC) of vancomycin on inhibition of planktonic MRSA growth (～ 25%) and biofilm formation (～ 50%). The CNPs–bacteria interaction force was up to 22 nN. Overall, these data suggest that CNPs have a good potential in clinical applications for the prevention and treatment of MRSA infection.     

Control of Staphylococcus aureus methicillin resistant isolated from auricular infections using aqueous and methanolic extracts of Ephedra alata

In the current study the potential use of aqueous and methanolic extracts of Ephedra alata aerial parts as biological control agent against pathogenic bacteria and especially Staphylococcus aureus methicillin resistant isolated from auricular infections was evaluated. Chemical tests and spectrophotometric methods were used for screening and quantification of phytochemicals. The assessment of the antioxidant activity was accomplished by DPPH and ABTS radicals scavenging assays. Extracts were evaluated for their antibacterial efficacy by diffusion and microdilution methods. Biofilm inhibition was tested using XTT assay and the cytotoxicity of extracts was carried out on Vero cell line. The GC-FID analysis revealed that E. alata was rich in unsatured fatty acids. In addition, the aqueous extract had the highest flavonoid and protein contents (30.82 mg QE /g dry extract and 98.92 mg BSAE/g dry extract respectively). However, the methanolic extract had the highest phenolic, sugars and tannins. The antioxidant activity demonstrated that the aqueous extract exhibited the strong potency (IC50 ranged between 0.001 and 0.002 mg/mL).Both extracts displayed antimicrobial activity on Gram negative and positive strains. They were effective against S. aureus isolated from auricular infections. The tested extracts were able to inhibit biofilm formation with concentration-dependent manner.Moreover, no cytotoxic effect on Vero cells line was demonstrated for the extracts. Overall, our findings highlight the potential use of E. alata extract as a novel source of bioactive molecules with antioxidant, antibacterial and antiobiofilm effects for the control of infectious disease especially those associated to S. aureus methicillin resistant.     

Biological evaluation and molecular modelling study of thiosemicarbazide derivatives as bacterial type IIA topoisomerases inhibitors

In the present article, we describe the inhibitory potency of nine thiosemicarbazide derivatives against bacterial type IIA topoisomerases, their antibacterial profile and molecular modelling evaluation. We found that one of the tested compounds, compound 7, significantly inhibits activity of Staphylococcus aureus DNA gyrase with an IC₅₀ below 15?μM. Besides, this compound displays antibacterial activity on reference Staphylococuss spp. and Enterococcus faecalis strains as well as clinical S. aureus isolates at non-cytotoxic concentrations in mammalian cells with MIC values ranging from 16 to 32?μg/mL thereby indicating, in some cases, equipotent or even more effective action than standard drugs such as vancomycin, ampicillin and nitrofurantoin. The computational studies showed that both molecular geometry and the electron density distribution have a great impact on antibacterial activity of thiosemicarbazide derivatives.     

Antimicrobial efficacy of extracts of Saudi Arabian desert Terfezia claveryi truffles

BackgroundTerfezia claveryi truffles are known for their nutritional value and have been considered among traditional treatments for ophthalmic infections and ailments.ObjectivesWe sought to investigate the in vitro antimicrobial efficacy of several T. claveryi extracts from Saudi Arabia. Certain pathogenic fungi and gram-negative and gram-positive bacteria were included.MethodsDry extracts were prepared using methanol, ethyl acetate, and distilled water, while the latter was used for preparing fresh extracts. The extracts were microbiologically evaluated through the disc-diffusion agar method; the zones of inhibition of microbial growth were measured post-incubation. The minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) were determined in Müller-Hinton Broth through the microdilution susceptibility method. anti-biofilm activity was assessed for potent extracts.ResultsDry extracts showed potent activity (>16-mm inhibition zones) against gram-positive (Bacillus subtilis IFO3007 and Staphylococcus aureus IFO3060) and gram-negative (Pseudomonas aeruginosa IFO3448 and Escherichia coli IFO3301) bacteria. The activity against fungi was moderate (12–16-mm inhibition zones) for both Aspergillus oryzae IFO4177 and Candida albicans IFO0583; there was no activity against Aspergillus niger IFO4414 growth. Methanolic extract had the lowest MIC and MBC, exhibiting remarkable activity against B. subtilis growth. Fresh extract showed moderate activity against bacterial growth and inactivity against fungal growth. Methanolic extract showed potent anti-biofilm activity (IC₅₀, 2.0 ± 0.18 mg/mL) against S. aureus.ConclusionsT. claveryi extracts showed antibacterial effects potentially suitable for clinical application, which warrants further in-depth analysis of their individual isolated compounds.     

In vitro anti- biofilm and anti-bacterial activity of Sesbania grandiflora extract against Staphylococcus aureus

The main objective of this research is to investigate the anti-biofilm and anti-bacterial activity of Sesbania grandiflora (S. grandiflora) against Staphylococcus aureus. S. grandiflora extract were prepared and analyzed with UV –Vis spectroscopy, Fourier transform infrared spectroscopy, Dynamic light scattering. Biofilm forming pathogens were identified by congo-red assay. Quantification of Extracellular polymeric substance (EPS) particularly protein and carbohydrate were calculated. The efficacy of the herbal extract S. grandiflora and its inhibition against the pathogenic strain of S. aureus was also evaluated. The gradual decrease or disappearance of peaks reveals the reduction of protein and carbohydrate content in the EPS of S. aureus when treated with S. grandiflora. The antibacterial activity of S. grandiflora extract against the bacterial strain S. aureus showed that the extract were more active against the strain. To conclude, anti-biofilm and antibacterial efficacy of S. grandiflora plays a vital role over biofilm producing pathogens and act as a good source for controlling the microbial population.     

Antioxidant and antibacterial activities of eugenol and carvacrol‐grafted chitosan nanoparticles

Essential oils are known to possess antimicrobial and antioxidant activity while chitosan is a biocompatible polymer with antibacterial activity against a broad spectrum of bacteria. In this work, nanoparticles with both antioxidant and antibacterial properties were prepared by grafting eugenol and carvacrol (two components of essential oils) on chitosan nanoparticles. Aldehyde groups were first introduced in eugenol and carvacrol, and the grafting of these oils to chitosan nanoparticles was carried out via the Schiff base reaction. The surface concentration of the grafted essential oil components was determined by X‐ray photoelectron spectroscopy (XPS). The antioxidant activities of the carvacrol‐grafted chitosan nanoparticles (CHCA NPs) and the eugenol‐grafted chitosan nanoparticles (CHEU NPs) were assayed with diphenylpicrylhydrazyl (DPPH). Antibacterial assays were carried out with a representative gram‐negative bacterium, Escherichia coli (E. coli) and a gram‐positive bacterium, Staphylococcus aureus (S. aureus). The grafted eugenol and carvacrol conferred antioxidant activity to the chitosan nanoparticles, and the essential oil component‐grafted chitosan nanoparticles achieved an antibacterial activity equivalent to or better than that of the unmodified chitosan nanoparticles. Cytotoxicity assays using 3T3 mouse fibroblast showed that the cytotoxicity of CHEU NPs and CHCA NPs were significant lower than those of the pure essential oils. Biotechnol. Bioeng. 2009; 104: 30–39 © 2009 Wiley Periodicals, Inc.