Allylsulfide constituents of garlic volatile oil as antimicrobial agents

Broad Antibacterial Activity and Mechanism of Garlic (Allium sativum L. cv. Uiseong) Extracts against Cell Wall of Aeromonas hydrophila

Aeromonas hydrophila is a pathogenic bacterium known for its resistance to antibiotics and its ability to cause infections in aquatic environments. This has made disease management more complex, making the development of alternative antimicrobial agents necessary. Uiseong garlic is a superior variety from Republic of Korea, renowned for its high level of beneficial compounds, making it a promising candidate for natural antimicrobial application. Therefore, this study aimed to investigate the antibacterial activity and mechanism of Uiseong garlic extracts against the cell wall of A. hydrophila. Uiseong garlic extracts were prepared using water and ethanol at 22°C and 90°C, respectively. The antibacterial activities of Uiseong garlic extracts were evaluated for their yield, antibacterial dynamics, leakage of bacterial intracellular proteins, and changes in morphological characteristics. Uiseong garlic extracts at 22°C exhibited significant antibacterial activities against foodborne pathogens, particularly against 9 strains of A. hydrophila. In this study, the ethanol extract at 22°C demonstrated significantly higher antibacterial activity compared to the water extract at 22°C, with a similar pattern of antimicrobial dynamics with polymyxin B. The ethanol extract at 22°C caused a higher concentration of leaked bacterial proteins (92.87 ± 0.46 μg/ml), indicating cell membrane disruption. Additionally, transmission electron microscopy analysis further confirmed that both extracts induced plasmolysis, leading to notable damage to the bacterial cell membrane. Therefore, ethanol extract of Uiseong garlic was demonstrated as a promising alternative to antibiotics for controlling A. hydrophila.

Selective influence of garlic as a key ingredient in kimchi on lactic acid bacteria in a fermentation model system

Garlic is an essential ingredient added to kimchi, a fermented vegetable, in small amounts owing to its sensory and antibacterial properties. This study aimed to elucidate the complex relationship between garlic and specific lactic acid bacteria (LAB) and the resulting metabolite changes in a controlled kimchi model system using nine strains as mixed and individual starters. The group without garlic using mixed starters showed the highest LAB growth activity, which influenced lactic acid production, pH, and titratable acidity. The group without garlic also showed differences in the composition of bacteria, such as Latilactobacillus sakei, Levilactobacillus brevis, unclassified Leuconostoc, and Weissella koreensis, during the fermentation period. In addition, the altering patterns of metabolites in the group without garlic during fermentation differed from those in the group with garlic. In addition, the metabolic profile of L. brevis group was mostly different from that of the other strains in the controlled model kimchi system using individual starters, suggesting that changes in LAB composition by garlic could subsequently affect metabolites during fermentation. This study provides valuable insights into the complex interactions among food ingredients, LAB succession, and metabolite production during fermentation.

Detection of Antibiotic Resistance in Feline-Origin ESBL Escherichia coli from Different Areas of China and the Resistance Elimination of Garlic Oil to Cefquinome on ESBL E. coli

The development of drug-resistance in the opportunistic pathogen Escherichia coli has become a global public health concern. Due to the share of similar flora between pets and their owners, the detection of pet-origin antibiotic-resistant E. coli is necessary. This study aimed to detect the prevalence of feline-origin ESBL E. coli in China and to explore the resistance elimination effect of garlic oil to cefquinome on ESBL E. coli. Cat fecal samples were collected from animal hospitals. The E. coli isolates were separated and purified by indicator media and polymerase chain reaction (PCR). ESBL genes were detected by PCR and Sanger sequencing. The MICs were determined. The synergistic effect of garlic oil and cefquinome against ESBL E. coli was investigated by checkerboard assays, time-kill and growth curves, drug-resistance curves, PI and NPN staining, and a scanning electronic microscope. A total of 80 E. coli strains were isolated from 101 fecal samples. The rate of ESBL E. coli was 52.5% (42/80). The prevailing ESBL genotypes in China were CTX-M-1, CTX-M-14, and TEM-116. In ESBL E. coli, garlic oil increased the susceptibility to cefquinome with FICIs from 0.2 to 0.7 and enhanced the killing effect of cefquinome with membrane destruction. Resistance to cefquinome decreased with treatment of garlic oil after 15 generations. Our study indicates that ESBL E. coli has been detected in cats kept as pets. The sensitivity of ESBL E. coli to cefquinome was enhanced by garlic oil, indicating that garlic oil may be a potential antibiotic enhancer.

Ability of Garlic and Ginger Oil to Reduce Salmonella in Post-Harvest Poultry

Approximately 1.35 million human salmonellosis cases are reported in the United States every year, resulting in over 26,000 hospitalizations and 400 deaths. Consumption of contaminated poultry products is one of the leading causes of human salmonellosis. Poultry meat becomes contaminated when feces from an infected bird comes into contact with the carcass during processing. Additional carcasses can then become cross-contaminated along the processing line. While chemicals such as peracetic acid are currently used to kill microbes such as Salmonella, consumers are increasingly calling for more natural alternatives. Our objective for this study was to determine the ability of the phytochemicals garlic and ginger oil to reduce Salmonella prevalence in the processing environment. In a simulated scalding tank environment, dipping contaminated chicken skin samples in a solution containing both garlic and ginger oil reduced Salmonella by up to 2 log CFU. Furthermore, the oils prevented Salmonella growth in the tank solution. The mechanism of action of garlic and ginger was evaluated using the sub-inhibitory concentration of each oil individually. While both were found to decrease autoinducer-2 (AI-2) levels, no effect was seen on expression of 10 genes involved in Salmonella virulence and survival. In total, this work demonstrates the potential of garlic and ginger to reduce Salmonella prevalence in the post-harvest environment. However, more work remains to be done to understand the mechanism of action.

Atherosclerosis amelioration by allicin in raw garlic through gut microbiota and trimethylamine-N-oxide modulation

Cardiovascular disease (CVD) is strongly associated with the gut microbiota and its metabolites, including trimethylamine-N-oxide (TMAO), formed from metaorganismal metabolism of ʟ-carnitine. Raw garlic juice, with allicin as its primary compound, exhibits considerable effects on the gut microbiota. This study validated the benefits of raw garlic juice against CVD risk via modulation of the gut microbiota and its metabolites. Allicin supplementation significantly decreased serum TMAO in ʟ-carnitine-fed C57BL/6 J mice, reduced aortic lesions, and altered the fecal microbiota in carnitine-induced, atherosclerosis-prone, apolipoprotein E-deficient (ApoE-/-) mice. In human subjects exhibiting high-TMAO production, raw garlic juice intake for a week reduced TMAO formation, improved gut microbial diversity, and increased the relative abundances of beneficial bacteria. In in vitro and ex vivo studies, raw garlic juice and allicin inhibited γ-butyrobetaine (γBB) and trimethylamine production by the gut microbiota. Thus, raw garlic juice and allicin can potentially prevent cardiovascular disease by decreasing TMAO production via gut microbiota modulation.

A glutathione responsive nanocarrier based on viologen resorcinarene cavitand and 1-allylthymine

A glutathione-sensitive nanocarrier for doxorubicin to improve cellular penetration and selective cytotoxic effects on T98G human glioblastoma cells.

Development of topical patches releasing allicin using garlic extract

INTRODUCTION

Treating hair loss of Alopecia areata is a quite challenge. The treatment not only needs to be effective but must meet specific requirements in terms of accurate dose, sustain release, comfortable application with aesthetic appearance. Thus, the study was designed to develop sustained release topical patches releasing allicin using different sources, including the extract from fresh and aged garlic, and commercially pure one.

METHODS

Patches were formulated by solvent casting method using ethylene-vinyl acetate as backing layer and Carbopol^® 971P NF (CP) as mucoadhesive polymer. Physicochemical properties were evaluated including weight, thickness, drug content, surface pH, moisture content, folding endurance, and swelling. In addition to in vitro diffusion study across the cellulose and Strat-M^® membranes.

RESULTS

Patches showed good physicochemical properties. No significant difference (p > 0.05) was obvious in the percentage of allicin diffused across cellulose membrane between patch A (loaded with commercial allicin), patch B1 (loaded with fresh garlic extract), and patch C (loaded with aged garlic extract). However, ethanol enhanced the diffusion of allicin. The percentage of allicin diffused across cellulose membrane over 20 h from patch E (45 mg CP, 2 mL fresh garlic extract-equivalent to 60 mg allicin-and 1 mL of ethanol) was 79.94%. The flux and permeability coefficients were 2.62 mg/cm² /h and 0.52 cm/h, respectively, with an enhancement ratio of 2.60 times the reference patch M (mashed garlic).

CONCLUSION

Promising development of topical patches of allicin using garlic extract as natural source with lower cost than the commercial pure allicin and higher aesthetic acceptance than the used mashed garlic.

Antibacterial Properties of Organosulfur Compounds of Garlic (Allium sativum)

Garlic (Allium sativum), a popular food spice and flavoring agent, has also been used traditionally to treat various ailments especially bacterial infections for centuries in various cultures around the world. The principal phytochemicals that exhibit antibacterial activity are oil-soluble organosulfur compounds that include allicin, ajoenes, and allyl sulfides. The organosulfur compounds of garlic exhibit a range of antibacterial properties such as bactericidal, antibiofilm, antitoxin, and anti-quorum sensing activity against a wide range of bacteria including multi-drug resistant (MDR) strains. The reactive organosulfur compounds form disulfide bonds with free sulfhydryl groups of enzymes and compromise the integrity of the bacterial membrane. The World Health Organization (WHO) has recognized the development of antibiotic resistance as a global health concern and emphasizes antibiotic stewardship along with the urgent need to develop novel antibiotics. Multiple antibacterial effects of organosulfur compounds provide an excellent framework to develop them into novel antibiotics. The review provides a focused and comprehensive portrait of the status of garlic and its compounds as antibacterial agents. In addition, the emerging role of new technologies to harness the potential of garlic as a novel antibacterial agent is discussed.

Antimicrobial Potential of Naturally Occurring Bioactive Secondary Metabolites

The use of traditional medicines of natural origin has been prevalent since ancient times globally as the plants produce a great diversity in their secondary metabolites. The naturally occurring bioactive constituents in food and other plant materials have shown widespread attention for their use as alternative medicine to prevent and cure microbial growth with the least toxic manifestations. The inclusion of these contents revealed their crucial role to improve the therapeutic efficacy of the classical drugs against various pathogenic microorganisms. Furthermore, several metabolites have also been explored in combination with antimicrobial agents to overcome the problems associated with drug resistance. This current review discusses the antimicrobial activities of secondary metabolites as well as their role in drug sensitivity against multiple-drug resistant pathogenic microbes.

Diallyl sulfide from garlic suppresses quorum-sensing systems of Pseudomonas aeruginosa and enhances biosynthesis of three B vitamins through its thioether group

Diallyl sulfide (DAS) and diallyl disulfide (DADS), two constituents of garlic, can inhibit quorum sensing (QS) systems of Pseudomonas aeruginosa. However, the differences in the mechanism of QS inhibition between DAS and DADS, and the functional chemical groups of these sulfides that contribute in QS inhibition have not been elucidated yet. We assumed that the sulfide group might play a key role in QS inhibition. To prove this hypothesis and to clarify these unsolved problems, in this study, we synthesized diallyl ether (DAE), and compared and investigated the effects of DAS and DAE on the growth and production of virulence factors, including Pseudomonas quinolone signal (PQS), elastase and pyocyanin, of P. aeruginosa PAO1. Transcriptome analysis and qRT‐PCR were used to compare and analyse the differentially expressed genes between the different treatment groups (DAS, DAE and control). The results indicated that DAS did not affect the growth dynamics of P. aeruginosa PAO1; however, DAS inhibited transcription of most of the QS system genes, including lasR, rhlI/rhlR and pqsABCDE/pqsR; thus, biosynthesis of the signal molecules C₄‐HSL (encoded by rhlI) and PQS (encoded by pqsABCDE) was inhibited. Furthermore, DAS inhibited the transcription of virulence genes regulated by the QS systems, including rhlABC, lasA, lasB, lecA and phzAB, phzDEFG, phzM and phzS that encode for rhamnolipid, exoprotease, elastase, lectin and pyocyanin biosynthesis respectively. DAS also enhanced the expression of the key genes involved in the biosynthesis of three B vitamins: folate, thiamine and riboflavin. In conclusion, DAS suppressed the production of some virulence factors toxic to the host and enhanced the production of some nutrition factors beneficial to the host. These actions of DAS may be due to its thioether group. These findings would be significant for development of an effective drug to control the virulence and pathogenesis of the opportunistic pathogen P. aeruginosa.

Headspace Characterization and Quantification of Aromatic Organosulfur Compounds in Garlic Extracts Using Surface-Enhanced Raman Scattering with a Mirror-in-a-Cap Substrate

Background

Surface-enhanced Raman scattering (SERS) has been deployed in the analysis of food at solid and aqueous states. However, its capability has not been fully explored in headspace profiling.

Objective

To develop an innovative SERS method for analyzing headspace volatile compounds in foods.

Methods

A volatile-capture device was developed by depositing a film of silver nanoparticles in a vial cap to capture the volatiles released from a model flavor compound (garlic).

Results

SERS peaks at 1632, 1400, 1291, 1191, 731, and 577 cm−1 were identified in the headspace of the garlic sample, which was representative of an organosulfur compound (diallyl disulfide), and its concentration was determined at 135 ppm, which was comparable to the value determined using GC. Preparation and analysis could be carried out in <10 min for the SERS method. The sensitivity of the SERS method (10 ppm), however, was slightly less than that of the GC method (5 pm).

Conclusions

The SERS method was able to quantify the concentration of diallyl disulfide in the headspace of a raw garlic ethanolic extract. Compared to GC, the SERS method had a much shorter analysis time and simpler sample preparation procedure than GC when analyzing large numbers of samples.

Highlights

The innovative “mirror-in-a-cap” substrate was simpler and faster than other reported SERS substrates used for this purpose. Additionally, SERS has much better portability and the potential for real-time monitoring of changes in the garlic headspace concentration during manufacturing and processing.

Allicin Modifies the Composition and Function of the Gut Microbiota in Alcoholic Hepatic Steatosis Mice

The intestinal microbiome plays an important role in the pathogenesis of liver diseases. Alcohol intake induces gut microbiota dysbiosis and alters its function. This study investigated the antibiotic effect of allicin in mice with hepatic steatosis. Male C57BL/6 mice were administered an ethanol diet supplemented with allicin (5 and 20 mg/(kg bw day)) for 4 weeks. Allicin modified the gut microbiota composition. Cecal microbiota exhibited a positive correlation with alcohol and hepatic triacylglycerol, but were suppressed with allicin. Ethanol diet with 5 mg of allicin induced a lower intestinal permeability compared to the ethanol diet alone. Allicin mediated the lipopolysaccharide (LPS)-CD14-toll-like receptor 4 (TLR4)-induced hepatic inflammation pathway by reducing LPS, CD14, TLR4, and pro-inflammatory cytokines-tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6. However, hepatic inflammation primarily resulted from alcohol toxicity rather than LPS production in the gut. The prediction of functional profiles from metagenomic 16S ribosomal RNA (rRNA) data revealed different functional profiles in each group. The predicted aldehyde dehydrogenase tended to increase in alcoholic mice administered allicin. The predicted LPS-related pathway and LPS biosynthesis protein results exhibited a similar trend as plasma LPS levels. Thus, alcohol and allicin intake shapes the gut microbiota and its functional profile and improves the CD14-TLR4 pathway to alleviate inflammation in the liver.

The Antifungal Effect of Garlic Essential Oil on Phytophthora nicotianae and the Inhibitory Component Involved

This study explored the chemical compositions of garlic essential oil, the inhibitory activity of garlic essential oil and diallyl disulfide (DADS) against Phytophthora nicotianae, and the effects on mycelial plasma membrane permeability and P. nicotianae inhibition. In total, 29 compounds were detected in garlic essential oil, of which 26 were detected by gas chromatography‒mass spectrometry (GC-MS) and 21 by headspace solid-phase microextraction (HS-SPME) GC-MS. DADS (60.12% and 19.09%) and trisulfide di-2-propenyl (14.18% and 17.98%) were the major components identified by HS-SPME GC-MS and GC-MS analysis, respectively. Half-inhibitory concentration (Ec50, antagonism) and minimum inhibitory concentration (MIC, fumigation) of DADS against P. nicotianae were 150.83 μL/L and 20 μL/L, respectively, while Ec50 of garlic essential oil was 1108.25 μL/L. Mycelial membrane permeability gradually increased in a concentration-dependent manner, and cell death increased at 450 μL/L DADS. Furthermore, DADS treatment significantly reduced the incidence of tobacco black shank and the number of P. nicotianae pathogens in rhizosphere soil. DADS also promoted root development of tobacco seedlings at low concentrations, which was inhibited at high concentrations. Therefore, DADS may play an important role in the antifungal effect against P. nicotianae by destroying mycelial cell membrane integrity, causing an increase in cell membrane permeability, and leading to cell death.

Inhibitory Activity of Plant Essential Oils against E. coli 1-Deoxy-d-xylulose-5-phosphate reductoisomerase

The rate-limiting enzyme of the 2-methyl-d-erythritol-4-phosphate (MEP) terpenoid biosynthetic pathway, 1-deoxy-d-xylulose-5-phosphate reductoisomerase (DXR), provides the perfect target for screening new antibacterial substances. In this study, we tested the DXR inhibitory effect of 35 plant essential oils (EOs), which have long been recognized for their antimicrobial properties. The results show that the EOs of Zanbthoxylum bungeanum (ZB), Schizonepetae tenuifoliae (ST), Thymus quinquecostatus (TQ), Origanum vulgare (OV), and Eugenia caryophyllata (EC) displayed weak to medium inhibitory activity against DXR, with IC₅₀ values of 78 μg/mL, 65 μg/mL, 59 μg/mL, 48 μg/mL, and 37 μg/mL, respectively. GC-MS analyses of the above oils and further DXR inhibitory activity tests of their major components revealed that eugenol (EC) and carvacrol (TQ and OV) possess medium inhibition against the protein (68.3% and 55.6%, respectively, at a concentration of 20 μg/mL), whereas thymol (ST, TQ, and OV), carveol (ZB), and linalool (ZB, ST, and OV) only exhibited weak inhibition against DXR, at 20 μg/mL (23%−26%). The results add more details to the antimicrobial mechanisms of plant EOs, which could be very helpful in the direction of the reasonable use of EOs in the food industry and in the control of phytopathogenic microbials.

Placebo-controlled study on the effects of oral administration of Allium sativum L in postweaning piglets

Postweaning diarrhoea (PWD) due to Escherichia coli is an economically important disease in pig production. In this placebo-controlled study performed in Switzerland, the effects of oral supplementation of Allium sativum L. (garlic, AS) on performance (bodyweight (BW) and daily weight gain (DWG)) and health (body condition and clinical score) were investigated in postweaning piglets. Piglets (n=600) were randomly assigned to the treatment groups (placebo, AS or colistin) and observed from birth until three weeks postweaning. The treatments were administered for the first two weeks postweaning. Faecal dry matter (FDM) and coliform bacteria on pen level were measured weekly. Data were analysed using generalised mixed-effect models in R. BW and DWG of the AS group were significantly higher compared with placebo in the third week postweaning. No differences in body condition and FDM were observed. The clinical score of AS-treated animals was significantly better compared with the colistin group. About 33 per cent of the piglets of the AS and the placebo group had to be treated with antibiotics due to the occurrence of severe PWD. The major finding of this study showed that AS supplementation increased growth performance and improved clinical health, but did not reduce the incidence and severity of PWD.

Antifungal activity of Gallesia integrifolia fruit essential oil

Gallesia integrifolia (Phytolaccaceae) is native to Brazil and has a strong alliaceous odor. The objective of this study was to identify the chemical composition of G. integrifolia fruit essential oil and evaluate fungicidal activity against the main food-borne diseases and food spoilage fungi. The essential oil was extracted by hydrodistillation and identified by GC-MS. From 35 identified compounds, 68% belonged to the organosulfur class. The major compounds were dimethyl trisulfide (15.49%), 2,8-dithianonane (52.63%) and lenthionine (14.69%). The utilized fungi were Aspergillus fumigatus, Aspergillus niger, Aspergillus ochraceus, Aspergillus versicolor, Penicillium funiculosum, Penicillium ochrochloron, Penicillium verrucosum var. cyclopium, and Trichoderma viride. Minimal fungicidal concentration for the essential oil varied from 0.02 to 0.18mg/mL and bifonazole and ketoconazole controls ranged from 0.20 to 3.50mg/mL. The lower concentration of the essential oil was able to control P. ochrochloron, A. fumigatus, A. versicolor, A. ochraceus and T. viride. This study shows a high fungicidal activity of G. integrifolia fruit essential oil and can support future applications by reducing the use of synthetic fungicides.

Diallyl disulfide from garlic oil inhibits Pseudomonas aeruginosa virulence factors by inactivating key quorum sensing genes

Garlic oil can disrupt the quorum sensing (QS) pathways of the opportunistic pathogen Pseudomonas aeruginosa; however, the underlying mechanisms for this effect are unclear. Diallyl disulfide (DADS) is one of the most abundant sulfur-containing compounds in garlic oil. This study investigated the effects of DADS on the growth, virulence factor production (elastase, pyocyanin, biofilm, and swarming motility), and essential gene expression of P. aeruginosa PAO1, particularly as they apply to QS and virulence. DADS at 1.28 mg/mL did not affect P. aeruginosa PAO1 growth, although it decreased elastase and pyocyanin production, biofilm formation, and swarming motility. Each of these phenomena is regulated by the three QS systems of P. aeruginosa PAO1 (las, rhl, and pqs). Real-time q-PCR revealed that DADS down-regulated the transcription levels of several important QS genes (lasI, lasR, rhlI, rhlR, pqsA, and pqsR) in the three systems. Furthermore, the transcription levels of QS-regulated virulence genes were also down-regulated. The lasB gene, encoding LasB elastase, is co-regulated by the las, rhl, and pqs systems, and thus the down-regulation of genes across the three systems further down-regulated lasB. Additionally, phzM (encoding pyocyanin), pslB (responsible for the production of a biofilm matrix polysaccharide), and chiC (encoding chitinase) were positively activated by LasR, and a decrease in lasR transcription further down-regulated the transcription of phzM, pslB, and chiC. Hence, DADS inhibits P. aeruginosa PAO1 virulence factors by inactivating the transcription of key genes across three different QS systems.

Antibacterial Effect of (2E,2E)-4,4-Trisulfanediylbis(but-2-enoic acid) against Staphylococcus aureus

A new highly active molecule, (2E, 2E)-4,4-trisulfanediylbis(but-2-enoic acid) (TSDB), was designed and synthesized through comparative molecular field analysis with the diallyl trisulfide structure of garlic. TSDB exerted a strong inhibitory effect against Staphylococcus aureus, with minimal inhibitory and minimal bactericidal concentrations of 16 and 128 μg/mL, respectively. TSDB destructed the integrity of the S. aureus cell membrane but weakly damaged the bacterial cell wall. TSDB also increased the conductivity and protein expression in microbial broth but minimally influenced the level of extracellular alkaline phosphatase. TSDB could be a novel food preservative.

COMPARATIVE STUDIES ON EFFECTS OF FREEZING ON PHYSICOCHEMICAL PROPERTIES OF FILLETS TWO FISH SPECIES IN IRAN

Because of fishes Sparidentex hasta and Pampus argenteus in the southern of Iran are consumed abundant in a particular season and it should be frozen for consumption throughout the year. Therefore, this research was carried out to investigate the effects of freezing on some of the physicochemical properties of fillets the fishes. Factors such as fat with chloroform-methanol method, amount of TBA (Thiobarbituric acid) in fish muscle accordance method of Pearson, pH using a pH meter, FFA (Free fatty acids) with titration in the presence of phenolphthalein was determined based on the percentage of oleic acid, peroxide value according to AOAC (Association of Official Analytical Chemists), in fresh samples at time zero and after different periods of freezing were tested respectively. Result showd that TBA (Thiobarbituric acid) content in fish fillet, found Pampus argenteus and Sparidentex hasta 0.65 and 0.53 respectively. The results showed that the highest percentage of fat found for Pampus argenteus at 95 days 24.2(%2) and for Sparidentex hasta at 35 days (25.19%), free fatty acids contents found highest (0.9%) and (0.97%) for Sparidentex hasta and Pampus argenteus after 95 days. It can conclude that the TBA (Thiobarbituric acid), FFA (Free fatty acids)  contents and pH of both fish species during storage in freezer were increased. Peroxide value in fish Pampus argenteus was reduced but, in Sparidentex hasta showed no significant differently.  The best time of storage of fishes Pampus argenteus and Sparidentex hasta at -18 °C was 35 days freezing, but nutritional value of fillets and fatty acids greatly reduced

A Possible Role for Singlet Oxygen in the Degradation of Various Antioxidants. A Meta-Analysis and Review of Literature Data

The thermodynamic parameters Eact, ΔH≠, ΔS≠, and ΔG≠ for various processes involving antioxidants were calculated using literature kinetic data (k, T). The ΔG≠ values of the antioxidants' processes vary in the range 91.27-116.46 kJmol-1 at 310 K. The similarity of the ΔG≠ values (for all of the antioxidants studied) is supported to be an indication that a common mechanism in the above antioxidant processes may be taking place. A value of about 10-30 kJmol-1 is the activation energy for the diffusion of reactants depending on the reaction and the medium. The energy 92 kJmol-1 is needed for the excitation of O₂ from the ground to the first excited state (¹Δg, singlet oxygen). We suggest the same role of the oxidative stress and specifically of singlet oxygen to the processes of antioxidants as in the processes of proteinaceous diseases. We therefore suggest a competition between the various antioxidants and the proteins of proteinaceous diseases in capturing singlet oxygen's empty π* orbital. The concentration of the antioxidants could be a crucial factor for the competition. Also, the structures of the antioxidant molecules play a significant role since the various structures have a different number of regions of high electron density.

Characterization of garlic endophytes isolated from the black garlic processing

The objectives of this study were to isolate and identify garlic endophytes, and explore the characteristics of dominant strains. Garlic endophytes were studied through phenotypical characterization and comparative sequence analysis of 16S rDNA based on culture‐dependent approaches. Representative strains inferred from 16S rDNA sequencing were selected for further identification by gyrA and rpoB gene loci and phylogenetic analysis based on concateneted house‐keeping sequences. Seven kinds of Bacillus were found from garlic and black garlic, respectively. Further studies demonstrated that the total bacteria and endophytes showed a sharp decrease firstly, followed by a rapid rise, then maintained at a certain level, and finally slowed down during the black garlic processing. B. subtilis, B. methylotrophicus, and B. amyloliquefaciens were the dominant strains. The selected strains were capable of fermenting glucose, lactose, sucrose, and garlic polysaccharide to produce acid but no gas, with a strong ability of heat resistance. The results indicated that there were a certain number of garlic endophytes during the black garlic processing, and Bacillus was the dominant strains under the conventional culture‐dependent methods. This report provided useful information for the presence and type of garlic endophytes during the black garlic processing, which were of great significance to study the formation mechanism and quality improvement of black garlic in the future, as well as the security of garlic powder.

Modulation of the multidrug efflux pump EmrD-3 from Vibrio cholerae by Allium sativum extract and the bioactive agent allyl sulfide plus synergistic enhancement of antimicrobial susceptibility by A. sativum extract

The causative agent of cholera, Vibrio cholerae, is a public health concern. Multidrug-resistant V. cholerae variants may reduce chemotherapeutic efficacies of severe cholera. We previously reported that the multidrug efflux pump EmrD-3 from V. cholerae confers resistance to multiple structurally distinct antimicrobials. Medicinal plant compounds are potential candidates for EmrD-3 efflux pump modulation. The antibacterial activities of garlic Allium sativum, although poorly understood, predicts that a main bioactive component, allyl sulfide, modulates EmrD-3 efflux. Thus, we tested whether A. sativum extract acts in synergy with antimicrobials and that a main bioactive component allyl sulfide inhibits EmrD-3 efflux. We found that A. sativum extract and allyl sulfide inhibited ethidium bromide efflux in cells harboring EmrD-3 and that A. sativum lowered the MICs of multiple antibacterials. We conclude that A. sativum and allyl sulfide inhibit EmrD-3 and that A. sativum extract synergistically enhances antibacterial agents.

Chemical composition and antimicrobial activity of garlic essential oils evaluated in organic solvent, emulsifying, and self-microemulsifying water based delivery systems

The chemical composition of garlic essential oils (GEOs) extracted from two different cultivars has been characterized using GC-MS analysis. GEO that was extracted from the white-skin cultivar (WGO) had a lower percentage of the major constituents diallyl trisulfide and diallyl disulfide (45.76 and 15.63%) than purple-skin cultivar (PGO) which contained higher percentages (58.53 and 22.38%) of the same components, respectively. Evaluation of the antimicrobial activity of WGO and PGO delivered in organic solvent (isopropanol) showed dose-dependent antimicrobial activity against the tested pathogenic bacteria and fungi, especially with WGO. On the other hand, formulation of both GEOs in water-based emulsions totally suppressed the antimicrobial activity of GEO. Re-formulation of GEOs in water-based microemulsion (particle size 10.1nm) showed better antimicrobial activity than emulsions at the same concentration of GEOs. This study can assist in designing the proper water-based delivery system of GEO for application in food preservation.

Garlic, from Remedy to Stimulant: Evaluation of Antifungal Potential Reveals Diversity in Phytoalexin Allicin Content among Garlic Cultivars; Allicin Containing Aqueous Garlic Extracts Trigger Antioxidants in Cucumber

Garlic has the charisma of a potent remedy and holds its repute of a therapeutic panacea since the dawn of civilization. An integrated approach was adopted to evaluate the genetic diversity among Chinese garlic cultivars for their antifungal potency as well as allicin content distribution and, furthermore; a bioassay was performed to study the bio-stimulation mechanism of aqueous garlic extracts (AGE) in the growth and physiology of cucumber (Cucumis sativus). Initially, 28 garlic cultivars were evaluated against four kinds of phytopathogenic fungi; Fusarium oxysporum, Botrytis cinerea, Verticillium dahliae and Phytophthora capsici, respectively. A capricious antifungal potential among the selected garlic cultivars was observed. HPLC fingerprinting and quantification confirmed diversity in allicin abundance among the selected cultivars. Cultivar G025, G064, and G074 had the highest allicin content of 3.98, 3.7, and 3.66 mg g(-1), respectively, whereas G110 was found to have lowest allicin content of 0.66 mg g(-1). Cluster analysis revealed three groups on the basis of antifungal activity and allicin content among the garlic cultivars. Cultivar G025, G2011-4, and G110 were further evaluated to authenticate the findings through different solvents and shelf life duration and G025 had the strongest antifungal activity in all conditions. minimum inhibitory concentration and minimum fungicidal concentration of Allicin aqueous standard (AAS) and AGE showed significant role of allicin as primary antifungal substance of AGE. Leaf disk bioassay against P. capsici and V. dahliae to comparatively study direct action of AGE and AAS during infection process employing eggplant and pepper leaves showed a significant reduction in infection percentage. To study the bioactivity of AGE, a bioassay was performed using cucumber seedlings and results revealed that AGE is biologically active inside cucumber seedlings and alters the defense mechanism of the plant probably activating reactive oxygen species at mild concentrations. However, at higher concentrations, it might cause lipid peroxidation and membrane damage which temper the growth of cucumber seedlings. At the outcome of the study, an argument is advanced that current research findings provide bases for cultivar selection in antifungal effectivity as well as genetic variability of the cultivars. Allicin containing AGE can be used in specialized horticultural situations such as plastic tunnel and organic farming as a bio-stimulant to enhance cucumber growth and attenuate fungal degradation of agricultural produce.

The Garlic Allelochemical Diallyl Disulfide Affects Tomato Root Growth by Influencing Cell Division, Phytohormone Balance and Expansin Gene Expression

Diallyl disulfide (DADS) is a volatile organosulfur compound derived from garlic (Allium sativum L.), and it is known as an allelochemical responsible for the strong allelopathic potential of garlic. The anticancer properties of DADS have been studied in experimental animals and various types of cancer cells, but to date, little is known about its mode of action as an allelochemical at the cytological level. The current research presents further studies on the effects of DADS on tomato (Solanum lycopersicum L.) seed germination, root growth, mitotic index, and cell size in root meristem, as well as the phytohormone levels and expression profile of auxin biosynthesis genes (FZYs), auxin transport genes (SlPINs), and expansin genes (EXPs) in tomato root. The results showed a biphasic, dose-dependent effect on tomato seed germination and root growth under different DADS concentrations. Lower concentrations (0.01-0.62 mM) of DADS significantly promoted root growth, whereas higher levels (6.20-20.67 mM) showed inhibitory effects. Cytological observations showed that the cell length of root meristem was increased and that the mitotic activity of meristematic cells in seedling root tips was enhanced at lower concentrations of DADS. In contrast, DADS at higher concentrations inhibited root growth by affecting both the length and division activity of meristematic cells. However, the cell width of the root meristem was not affected. Additionally, DADS increased the IAA and ZR contents of seedling roots in a dose-dependent manner. The influence on IAA content may be mediated by the up-regulation of FZYs and PINs. Further investigation into the underlying mechanism revealed that the expression levels of tomato EXPs were significantly affected by DADS. The expression levels of EXPB2 and beta-expansin precursor were increased after 3 d, and those of EXP1, EXPB3 and EXLB1 were increased after 5 d of DADS treatment (0.41 mM). This result suggests that tomato root growth may be regulated by multiple expansin genes at different developmental stages. Therefore, we conclude that the effects of DADS on the root growth of tomato seedlings are likely caused by changes associated with cell division, phytohormones, and the expression levels of expansin genes.

The dynamics and mechanism of the antimicrobial activity of tea tree oil against bacteria and fungi

Tea tree oil (TTO) is a yellow liquid extracted from Melaleuca alternifolia. Although the antimicrobial activity of TTO has been known for a long time, its specific antimicrobial effects and mechanism underlying these remain poorly characterized. The present study investigated the chemical composition of TTO and the dynamics and mechanism of its antimicrobial activities in two bacterial and two fungal strains. Gas chromatography-mass spectrometry analysis identified alkenes and alcohols as the main constituents of TTO. Terpinen-4-ol was the most abundant individual component, accounting for approximately 23 % of the TTO. Poisoned food technique assessment showed that the minimum inhibitory concentrations of TTO for bacterial strains (Escherichia coli and Staphylococcus aureus) and fungal strains (Candida albicans and Aspergillus niger) were 1.08 and 2.17 mg/mL, respectively. Antimicrobial dynamic curves showed that with increasing concentrations of TTO, the rate of cell killing and the duration of growth lag phase increased correspondingly. These data indicated that TTO produced concentration and time-dependent antimicrobial effects. The minimum bactericidal and fungicidal concentrations of TTO were 2.17, 4.34, and 4.34 against E. coli, S. aureus, and C. albicans, respectively. However, A. niger conidia were not completely eradicated, even after 3 days in the presence of 17.34 mg/mL TTO. Transmission electron microscopy images indicated that TTO penetrated the cell wall and cytoplasmic membrane of all the tested bacterial and fungal strains. TTO may also penetrate fungal organelle membrane. These findings indicated that TTO maybe exerts its antimicrobial effects by compromising the cell membrane, resulting in loss of the cytoplasm and organelle damage, which ultimate leads to cell death.

Antileishmanial and Immunomodulatory Activity of Allium sativum (Garlic): A Review

Leishmaniasis is caused by an obligate intracellular protozoa belonging to Leishmania genus. The current drugs for treatment of leishmaniasis possess many disadvantages; therefore, researchers are continuously looking for the more effective and safer drugs. The aim of this study is to review the effectiveness, toxicities, and possible mechanisms of pharmaceutical actions of different garlic extracts and organosulfur compounds isolated from garlic against Leishmania spp. in a variety of in vitro, in vivo and clinical trials reports. All relevant databases were searched using the terms "Allium sativum," "Garlic," "Allicin," "Ajoene," "Leishmania," "in vitro," "in vivo," and "clinical trial," alone or in combination from 5 English databases (Web of Science, PubMed, Science Direct, Scopus, Google Scholar) and 3 Persian databases (Scientific Information Database, Iran Medex, and Magiran) from 1990 to 2014. In summary, garlic with immunomodulatory effects and apoptosis induction contributes to the treatment of leishmaniasis.

The role of spices and lactic acid bacteria as antimicrobial agent to extend the shelf life of metata ayib (traditional Ethiopian spiced fermented cottage cheese)

Spices and lactic acid bacteria have natural antimicrobial substances and organic compounds having antagonistic activity against microorganisms. The objective of this study was to investigate the role of spices and lactic acid bacteria as antimicrobial agent to extend the shelf life of metata ayib. Antimicrobial activities of spices and lactic acid bacteria (LAB) filtrates were determined by agar well diffusion method against E. coli, S. aureus, S. flexneri and S. peumoniae. Aantimicrobial activity of garlic was found to be the most effective against all the tested pathogens. Inhibition zones of garlic extract against all pathogens was significantly (P ≤ 0.05) greater than the remaining spice extracts. Inhibition zones (12.50 ± 1.00 to 15.50 ± 1.00 mm) of ginger and R. graveolens ethanol extracts against all tested pathogens were significantly (P ≤ 0.05) greater than the remaining solvent extracts. Inhibition zone of O. basilicum ethanol extract against all pathogenic bacteria was significantly (p ≤ 0.05) greater than hexane and acetone extracts. Lactobacillus isolates were shown the highest antimicrobial activity than the other LAB isolates against all pathogens. The synergistic effect of spices together with LAB might be contributed a lot to preserve and extend shelf life of metata ayib. Their antimicrobial activity can reduce the risk of spoilage and pathogenesis. The possible reason of LAB isolates was may be due to production of lactic acid, acetic acid and secondary metabolites like bacteriocins. Aseptic processing of traditional cottage cheese (ayib) is by far needed to minimize risks associated during consumption of metata ayib.

Antibacterial activity and kinetics of Litsea cubeba oil on Escherichia coli

Litsea cubeba oil is extracted from the fresh fruits of Litsea cubeba by distillation. In this study, its chemical constituents, antibacterial activity, kinetics and effects against Escherichia coli were studied. Its minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were both 0.125% (v/v) by toxic food method. Moreover, the antibacterial kinetic curves indicated 0.0625% (v/v) of litsea cubeba oil was able to prolong the growth lag phase of E. coli cells to approximate 12 hours while 0.125% (v/v) of litsea cubeba oil was able to kill the cells completely. Furthermore, transmission electron microscope (TEM) observation showed most E. coli cells treated with 0.125% (v/v) of litsea cubeba oil were killed or destroyed severely within 2 hours. The litsea cubeba oil might penetrate and destroy the outer and inner membrane of E. coli cells. Thus many holes and gaps were observed on the damaged cells, which led to their death eventually. The antibacterial effects of litsea cubeba oil mainly attributed to the presence of aldehydes, which accounted for approximately 70% in its whole components analyzed by GC/MS. Based on the antimicrobial properties, litsea cubeba oil would have a broad application in the antimicrobial industry.

Antifungal effect and mechanism of garlic oil on Penicillium funiculosum

Garlic oil is a kind of fungicide, but little is known about its antifungal effects and mechanism. In this study, the chemical constituents, antifungal activity, and effects of garlic oil were studied with Penicillium funiculosum as a model strain. Results showed that the minimum fungicidal concentrations (MFCs, v/v) were 0.125 and 0.0313 % in agar medium and broth medium, respectively, suggesting that the garlic oil had a strong antifungal activity. The main ingredients of garlic oil were identified as sulfides, mainly including disulfides (36 %), trisulfides (32 %) and monosulfides (29 %) by gas chromatograph-mass spectrometer (GC/MS), which were estimated as the dominant antifungal factors. The observation results by transmission electron microscope (TEM) and scanning electron microscope (SEM) indicated that garlic oil could firstly penetrate into hyphae cells and even their organelles, and then destroy the cellular structure, finally leading to the leakage of both cytoplasm and macromolecules. Further proteomic analysis displayed garlic oil was able to induce a stimulated or weakened expression of some key proteins for physiological metabolism. Therefore, our study proved that garlic oil can work multiple sites of the hyphae of P. funiculosum to cause their death. The high antifungal effects of garlic oil makes it a broad application prospect in antifungal industries.

Comparitive study on volatile aroma compounds of two different garlic types (Kastamonu and Chinese) using gas chromatography mass spectrometry (HS-GC/MS) technique

BACKROUND

The medicinal use of garlic is much older than its usage as a food. The medical importance of garlic comes forward for its sulfur-containing components. In this study, it was aimed to compare Kastamonu garlic type with Chinese garlic type based on their aroma profiles.

MATERIALS AND METHODS

Fresh Kastamonu garlic samples harvested from Kastamonu region of Turkey and Chinese garlic samples obtained from Turkish market were used as plant material. Volatile aroma compounds were determined using Headspace Gas Chromatography Mass Spectrometry (HS-GC/MS).

RESULTS

Sixteen and twenty aroma components were identified in Kastamonu and Chinese garlic types, respectively. Kastamonu garlic type was found to be richer than Chinese garlic types in terms of sulfur-containing compounds. Diallyl disulphide, which is one of these components, was detected at level of 41.87% and 34.95% in the Kastamonu and Chinese garlic types, respectively. Also di-2-propenyl trisulfide was found only in Kastamonu garlic types. Disulfide, methyl 2-propenyl was determined at similar levels in both garlic types.

CONCLUSION

The majority of garlic grown in Kastamonu region of Turkey is assessed by medical companies.

CONCLUSION

The results of the current study showed that Kastamonu garlic type has important medical properties. Therefore, this garlic can also be used in the medical field, as well as the consumption as food.

Computational identification and characterization of conserved miRNAs and their target genes in garlic (Allium sativum L.) expressed sequence tags

The endogenous small non-coding functional microRNAs (miRNAs) are short in size, range from ~21 to 24 nucleotides in length, play a pivotal role in gene expression in plants and animals by silencing genes either by destructing or blocking of translation of homologous mRNA. Although various high-throughput, time consuming and expensive techniques like forward genetics and direct cloning are employed to detect miRNAs in plants but comparative genomics complemented with novel bioinformatic tools pave the way for efficient and cost-effective identification of miRNAs through homologous sequence search with previously known miRNAs. In this study, an attempt was made to identify and characterize conserved miRNAs in garlic expressed sequence tags (ESTs) through computational means. For identification of novel miRNAs in garlic, a total 3227 known mature miRNAs of plant kingdom Viridiplantae were searched for homology against 21,637 EST sequences resulting in identification of 6 potential miRNA candidates belonging to 6 different miRNA families. The psRNATarget server predicted 33 potential target genes and their probable functions for the six identified miRNA families in garlic. Most of the garlic miRNA target genes seem to encode transcription factors as well as genes involved in stress response, metabolism, plant growth and development. The results from the present study will shed more light on the understanding of molecular mechanisms of miRNA in garlic which may aid in the development of novel and precise techniques to understand some post-transcriptional gene silencing mechanism in response to stress tolerance.

Brown seaweed (Saccharina japonica) as an edible natural delivery matrix for allyl isothiocyanate inhibiting food-borne bacteria

The edible, brown seaweed Saccharina japonica was prepared as powder in the size range 500-900 μm for the desorption release of allyl isothiocyanate (AITC). Powders were used as raw (containing lipids) and as de-oiled, where the lipid was removed. In general, de-oiled powders adsorbed larger masses of AITC after vapour or solution contact. Mass adsorbed due to solution contact exceeded vapour contact. Larger particles adsorbed more than smaller particles. No chemical bonding between AITC and the powder surface occurred. Release from vapour deposited particles reached 70-85% available within 72 h; solution deposited reached 70-90% available at 192 h. The larger amounts of AITC adsorbed via solution deposition resulted in greater vapour-phase concentrations at 72 h for antimicrobial activity studies. No loss of activity was detected against Escherichia coli, Salmonella Typhimurium or Bacillus cereus. Only a nominal activity against Staphylococcus aureus was demonstrated. S. japonica powder could be used as an edible, natural vehicle for AITC delivery.

Antibacterial activity of selected Cameroonian dietary spices ethno-medically used against strains of Mycobacterium tuberculosis

ETHNOPHARMACOLOGICAL RELEVANCE

Tuberculosis (TB) is considered as a re-emerging disease and one of the most important public health problems worldwide. The use or (in most cases) misuse of existint anti-tuberculosis drugs over the years has led to an increasing prevalence of resistant strains, establishing an urgent need to search for new effective agents. Spices are largely used ethno-medically across Africa.

AIM OF THE STUDY

The present study aimed to evaluate the in vitro antimycobacterial activities of a total of 20 methanol crude extracts prepared from 20 Cameroonian dietary spices for their ability to inhibit the growth of or kill Mycobacterium tuberculosis strains H(37)Rv (ATCC 27294) and H(37)Ra (ATCC 25177).

MATERIALS AND METHODS

The antituberculosis screening was performed using the Microplate Alamar Blue Assay (MABA) method to determine the minimum inhibitory concentration (MIC) and the minimum mycobactericidal concentration (MBC).

RESULTS

Fifteen (15) plant extracts out of 20 showed varied levels of antimycobacterial activity against the strains M. tuberculosis H(37)Rv and H(37)Ra, with MICs in the range of 2.048-0.016 mg/ml. The extract of Echinops giganteus exhibited the most significant activity with a MIC value of 32 μg/ml and 16 μg/ml, respectively against H(37)Ra and H(37)Rv. To the best of our knowledge, the antimycobacterial activity of the tested spices has not been reported before and therefore our results can be evaluated as the first report about the antimycobacterial properties.

CONCLUSIONS

The results of this study suggest that Echinops giganteus and Piper guineense could be important sources of bactericidal compounds against M. tuberculosis and could probably be promising candidates that can be further investigated.

Inhibitory effect of Allium sativum and Zingiber officinale extracts on clinically important drug resistant pathogenic bacteria

BACKGROUND

Herbs and spices are very important and useful as therapeutic agent against many pathological infections. Increasing multidrug resistance of pathogens forces to find alternative compounds for treatment of infectious diseases.

METHODS

In the present study the antimicrobial potency of garlic and ginger has been investigated against eight local clinical bacterial isolates. Three types of extracts of each garlic and ginger including aqueous extract, methanol extract and ethanol extract had been assayed separately against drug resistant Escherichia coli, Pseudomonas aeruginosa, Bacillus subtilis, Staphylococcus aureus, Klebsiella pneumoniae, Shigella sonnei, Staphylococcusepidermidis and Salmonella typhi. The antibacterial activity was determined by disc diffusion method.

RESULTS

All tested bacterial strains were most susceptible to the garlic aqueous extract and showed poor susceptibility to the ginger aqueous extract. The (minimum inhibitory concentration) MIC of different bacterial species varied from 0.05 mg/ml to 1.0 mg/ml.

CONCLUSION

In the light of several socioeconomic factors of Pakistan mainly poverty and poor hygienic condition, present study encourages the use of spices as alternative or supplementary medicine to reduce the burden of high cost, side effects and progressively increasing drug resistance of pathogens.

An Overview of Antimicrobial Properties of Different Classes of Phytochemicals

Plants produce a great diversity of phytochemicals, the beneficial properties of which have been used by humans for centuries since the advent of human civilization. With the discovery of effective and potent antimicrobial compounds, these synthetic antimicrobial compounds are widely used to prevent and cure microbial diseases. However, the development of antibiotic resistant strains of bacteria, reduced efficacy and safety of antimicrobials and the search of new antimicrobials against emerging incurable diseases by conventional antimicrobial agents have revived to explore phytochemicals as an alternative to synthetic antimicrobial compounds. Although numerous studies have been conducted in vitro and in vivo in the recent years on the efficacy of plant phytochemicals as antimicrobial agents, this chapter provides an overview of the antimicrobial properties of some major group of phytochemicals, namely, different phenolic compounds, alkaloids, saponins, iridoids and secoiridoids, polyacetylenes, glucosinolates, terpenoids, sulfinate, limonoids (tetranortepenoids) and anthranoids against pathogenic bacteria, fungi, viruses and commensal bacteria in the intestinal tracts of humans and animals. This chapter also discusses their antimicrobial mechanisms of action, the efficiency of different groups of phytochemicals against multiple-drug resistant bacteria, the effect of active dietary phytometabolites on the beneficial and pathogenic microbes of the gastrointestinal tracts and the outcomes of combination of phytofactors and drugs interactions.

In vitro efficacy of diallyl sulfides against the periodontopathogen Aggregatibacter actinomycetemcomitans

The in vitro antibacterial effects of diallyl sulfide (DAS) against the Gram-negative periodontopathogen Aggregatibacter actinomycetemcomitans, the key etiologic agent of the severe form of localized aggressive periodontitis and other nonoral infections, were studied. A. actinomycetemcomitans was treated with garlic extract, allicin, or DAS, and the anti-A. actinomycetemcomitans effects of the treatment were evaluated. Garlic extract, allicin, and DAS significantly inhibited the growth of A. actinomycetemcomitans (greater than 3 log; P < 0.01) compared to control cells. Heat inactivation of the garlic extracts significantly reduced the protein concentration; however, the antimicrobial effect was retained. Purified proteins from garlic extract did not exhibit antimicrobial activity. Allicin lost all its antimicrobial effect when it was subjected to heat treatment, whereas DAS demonstrated an antimicrobial effect similar to that of the garlic extract, suggesting that the antimicrobial activity of garlic extract is mainly due to DAS. An A. actinomycetemcomitans biofilm-killing assay performed with DAS showed a significant reduction in biofilm cell numbers, as evidenced by both confocal microscopy and culture. Scanning electron microscopy (SEM) analysis of DAS-treated A. actinomycetemcomitans biofilms showed alterations of colony architecture indicating severe stress. Flow cytometry analysis of OBA9 cells did not demonstrate apoptosis or cell cycle arrest at therapeutic concentrations of DAS (0.01 and 0.1 μg/ml). DAS-treated A. actinomycetemcomitans cells demonstrated complete inhibition of glutathione (GSH) S-transferase (GST) activity. However, OBA9 cells, when exposed to DAS at similar concentrations, showed no significant differences in GST activity, suggesting that DAS-induced GST inhibition might be involved in A. actinomycetemcomitans cell death. These findings demonstrate that DAS exhibits significant antibacterial activity against A. actinomycetemcomitans and that this property might be utilized for exploring its therapeutic potential in treatment of A. actinomycetemcomitans-associated oral and nonoral infections.