Genetic screening of wine‐related enzymes in Lactobacillus species isolated from South African wines

Aims: The objective of this study was to investigate the presence of genes coding for enzymes of oenological relevance in wine Lactobacillus strains isolated from South African grape and wine samples during the 2001 and 2002 harvest seasons. Methods and Results: A total of 120 wine lactobacilli isolates belonging to Lactobacillus plantarum, Lactobacillus hilgardii, Lactobacillus brevis, Lactobacillus pentosus, Lactobacillus paracasei, Lactobacillus sakei and Lactobacillus paraplantarum were genetically screened for enzyme‐encoding genes using PCR with primers specific for β‐glucosidase, protease, esterase, citrate lyase and phenolic acid decarboxylase. The results of PCR screening showed that the Lactobacillus strains possessed different combinations of enzymes and that some strains did not possess any of the enzymes tested. Confirmation analysis with gene sequencing also showed high similarity of genes with those available in GenBank database. Conclusion: In this study, we have demonstrated the existence of genes coding for wine‐related enzymes in wine lactobacilli that could potentially hydrolyse wine precursors to positively influence wine aroma. Significance and Impact of the Study: An expansion of knowledge on the genetic diversity of wine‐associated lactic acid bacteria will enable the selection of novel malolactic fermentation starter cultures with desired oenological traits for the improvement of the organoleptic quality of the wine, and hence wine aroma.     

Recovery of bioactive compounds from white grape (Vitis vinifera L.) stems as potential antimicrobial agents for human health

The grape is a matrix rich in bioactive compounds and its production generates large quantities of by-products, such as grape stems, which, to date, present low commercial value. However, there is a growing interest in the application of this material as a source of phenolic compounds. Therefore, the present study aims at assessing the phytochemical profile of (poly)phenolic extracts of white Portuguese grape stem varieties produced in the Região Demarcada do Douro (Portugal). The antioxidant activity determined by several assays, as well as the antimicrobial activity using the disc diffusion method against human gastrointestinal pathogenic bacteria of the hydromethanolic extracts, were evaluated. This work presents very positive results as the rich composition in phenolic compounds (94.71–123.09 mg GA⁻¹ and 0.02–73.79 mg g⁻¹ for the total phenol content and for individual phenolics, respectively) presented by grape stems can explain the high antioxidant (0.37–1.17 mmol Trolox g⁻¹) and antimicrobial activities against, essentially, Gram-positive bacteria, and in some cases with higher efficacy than commercial antibiotics. Thus, demonstrating that this wine by-product should deserve greater attention from the pharmaceutical industries due to its excellent biological properties and characteristics not yet applied.     

Study of the Biological Activity and Phenolic Content of the Ethanol Extract of Phyllogonium viride Brid. (Phyllogoniaceae,Bryophyta)

The present study aimed to examine the phenolic content and evaluate the antimicrobial and antioxidant potential of ethanol extracts from the moss species Phyllogonium viride Brid. on the pathogenic bacteria Salmonella enterica serovar enteritidis, Staphylococcus aureus, Listeria monocytogenes and Escherichia coli, and the pathogenic fungi Candida albicans and Cryptococcus neoformans. The antimicrobial activity was determined from Minimum Inhibitory Concentration (MIC) Minimum Bactericidal Concentration (MBC) and Minimum Fungicidal Concentration (MFC). Antioxidant activity was determined by the DPPH method. Folin-Denis reagent was used for the content of total phenolics and flavonoids and HPLC-DAD for identification of phenolic compounds. The results showed that bacteriostatic and bactericidal activities occurred at concentrations ranging from 9.76 μg/mL–78.13 μg/mL among all evaluated microorganisms. These values, considering the criteria used, suggest the P. viride extract as a potent antimicrobial. For antioxidant activity, P. viride extract was considered weak. Analysis of the phenolic content showed a wide range of compounds, with Kaempferol (0.41 mg/g) being the major compound, followed by t-cinnamic acid and caffeic acid (0.17 mg/g). Although P. viride is a species of moss not yet referenced in scientific publications of biotechnological interest, it has shown promising potential for further studies and possible application as an antimicrobial of natural origin.     

Sensitivity to vinyl phenol derivatives produced by phenolic acid decarboxylase activity in Escherichia coli and several food-borne Gram-negative species

Ferulic, p-coumaric, and caffeic acids are phenolic acids present in soil, food, and gut, which have antimicrobial effects. Some Gram (+) bacteria metabolize these phenolic acids into vinyl derivatives due to phenolic acid decarboxylase activity (PAD) involved in the phenolic acid stress response (PASR). In this study, the antimicrobial activity of phenolic acids and their vinyl derivatives was tested on a panel of desirable and undesirable food-borne bacteria, especially Gram (?) species of Salmonella, Enterobacter, Klebsiella, and Pseudomonas, most of them without PAD activity. Native and engineered Escherichia coli strains either expressing or not PAD activity were included. Gram (?) bacteria of the panel were not significantly inhibited by phenolic acids at 3 mM, but were dramatically inhibited by the corresponding vinyl derivatives. On the contrary, Gram (+) bacteria displaying the PASR face the toxicity of phenolic acids by PAD activity and are not inhibited by vinyl phenols. In E. coli, the genes aaeB and marA, encoding efflux pumps for antimicrobial compounds, are upregulated by the addition of p-coumaric acid, but not by its derivative 4-vinyl phenol (p-hydroxystyrene). These results suggest that phenolic acids and their vinyl phenol derivatives produced by PAD (+) species could have a significant impact on undesirable or pathogenic food-borne Gram (?) bacteria in complex microbial ecosystems.     

Copper Oxide Nanomaterials Derived from Zanthoxylum armatum DC. and Berberis lycium Royle Plant Species: Characterization,Assessment of Free Radical Scavenging and Antibacterial Activity

Copper oxide nanomaterials were synthesized by a facile sustainable biological method using two plant species (Zanthoxylum armatum DC. and Berberis lycium Royle ). The formation of materials was confirmed by FT‐IR, ATR, UV‐visible, XRD, TEM, SEM, EDX, TGA and PL. The antibacterial activity was evaluated by agar well diffusion method to ascertain the efficacy of plant species extract and extract derived copper oxide nanomaterials against six Gram‐positive bacteria namely Staphylococcus aureus, Streptococcus mutans, Streptococcus pyogenes, Corynebacterium diphtheriae, Corynebacterium xerosis, Bacillus cereus and four Gram‐negative bacteria such as Klebsiella pneumonia, Escherichia coli, Pseudomonas aeruginosa and Proteus vulgaris against the standard drug, Ciprofloxacin for Gram‐positive and Gentamicin for Gram‐negative bacteria, respectively. In both cases, copper oxide nanomaterials were found to be sensitive in all the bacterial species. Sensitivity of copper oxide nanomaterials shows an be higher as compared to plant species extract against different bacteria. Scavenging activity of plant extracts along with nanomaterials have been accessed using previously reported protocols employing ascorbic acid as standard. Scavenging activity of copper oxide nanomaterials shows an increase with increase in concentration. The biological activity (bactericidal and scavenging efficiency) of plant derived copper oxide nanomaterials revealed that these materials can be used as potent antimicrobial agent and DPPH scavengers in industrial as well as pharmacological fields.     

Antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20

Aims: The aim of this study was to determine the antimicrobial and antiadhesive properties of a biosurfactant isolated from Lactobacillus paracasei ssp. paracasei A20 against several micro‐organisms, including Gram‐positive and Gram‐negative bacteria, yeasts and filamentous fungi. Methods and Results: Antimicrobial and antiadhesive activities were determined using the microdilution method in 96‐well culture plates. The biosurfactant showed antimicrobial activity against all the micro‐organisms assayed, and for twelve of the eighteen micro‐organisms (including the pathogenic Candida albicans, Escherichia coli, Staphylococcus aureus, Staphylococcus epidermidis and Streptococcus agalactiae), the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were achieved for biosurfactant concentrations between 25 and 50 mg ml^?1. Furthermore, the biosurfactant showed antiadhesive activity against most of the micro‐organisms evaluated. Conclusions: As far as we know, this is the first compilation of data on antimicrobial and antiadhesive activities of biosurfactants obtained from lactobacilli against such a broad group of micro‐organisms. Although the antiadhesive activity of biosurfactants isolated from lactic acid bacteria has been widely reported, their antimicrobial activity is quite unusual and has been described only in a few strains. Significance and Impact of the Study: The results obtained in this study regarding the antimicrobial and antiadhesive properties of this biosurfactant opens future prospects for its use against micro‐organisms responsible for diseases and infections in the urinary, vaginal and gastrointestinal tracts, as well as in the skin, making it a suitable alternative to conventional antibiotics.     

Influence of epigallocatechin gallate and phenolic compounds from green tea on the growth of Oenococcus oeni

Aims: To investigate the effect of phenolic compounds on the growth of Oenococcus oeni. Methods and Results: Oenococci are usually grown in media often supplemented with complex additives such as tomato juice. In order to improve our knowledge about the growth requirements of oenococci, we added several juices and leaf extracts such as green tea to the culture media and screened them for growth‐stimulating substances to substitute complex supplements such as juices by more defined components. We found that also green tea could cause a growth stimulation of Oenococcus oeni strain B2. Conclusions: Further experiments showed that the stimulating effect was as a result of the phenolic compounds of green tea, especially epigallocatechin gallate (EGCG). On the other hand, EGCG could also inhibit the growth of O. oeni strain B2 just depending on its concentration. Significance and Impact of the Study: Individual catechins should have a minor influence on the growth of oenococci during wine making as their concentration in grapes is <30 mg kg^?1 grape. Whether there is a synergistic effect of the different catechins in wine has to be investigated.     

Laserpitium zernyi Hayek Flower and Herb Extracts: Phenolic Compounds,and Anti‐edematous,Antioxidant, and Antimicrobial Activities

Phenolic compounds and different biological activities of the dry MeOH extracts of the flowers and the herb (aerial parts without flowers) of Laserpitium zernyi Hayek (Apiaceae) were investigated. The total phenolic contents in the extracts were determined spectrophotometrically using Folin–Ciocalteu reagent. In both extracts, apigenin, luteolin, their 7‐O ‐glucosides, and chlorogenic acid were detected by HPLC . Identified phenolics were quantified in both extracts, except luteolin in L . zernyi herb extract. The extracts (p.o .) were tested for anti‐edematous activity in a model of carrageenan (i.pl .) induced rat paw edema. Antioxidant activity of the extracts was assessed by FRAP assay and DPPH and ^?OH radicals scavenging tests. Antimicrobial activity was investigated using broth microdilution test against five Gram ‐positive and three Gram ‐negative bacteria, as well as against two strains of Candida albicans . The polyphenol‐richer flower extract exerted higher anti‐edematous and antioxidant activities. The herb extract exhibited better antimicrobial effect against Micrococcus luteus , Enterococcus faecalis , Bacillus subtilis , and Pseudomonas aeruginosa , while against other tested microorganisms, the activity of both extracts was identical. Demonstrated biological activities of L . zernyi flower and herb extracts represent a good basis for their further investigation as potential new herbal medicinal raw materials.     

Comparison of the Composition and Antimicrobial Activities of the Essential Oils of Green Branches and Leaves of Egyptian Navel Orange (Citrus sinensis (L.) Osbeck var. malesy)

The essential oils isolated from the leaves and green branches of the Egyptian navel orange trees were analyzed by GC and GC/MS. A total of 33 and 24 compounds were identified from the oils of the leaves and branches accounting for 96.0% and 97.9%, respectively, of the total detected constituents. The major ones were sabinene (36.5; 33.0%), terpinen‐4‐ol (8.2; 6.2%), δ‐3‐carene (7.0; 9.4%), limonene (6.8; 18.7%), trans‐ocimene (6.7; 6.1%), and β‐myrcene (4.5; 4.4%). The antimicrobial activities of both oils were evaluated using the agar‐well diffusion method toward three representatives for each of Gram‐positive bacteria, Gram‐negative bacteria, and fungi. The oil of leaves was more effective as antimicrobial agent than that of the branches. Streptococcus pyogenes, Staphylococcus aureus, Salmonella typhimurium, and Aspergillus fumigatus were the most sensitive bacteria and fungi by the leaves oil.     

In vitro anti-bacterial and anti-adherence effects of natural polyphenolic compounds on oral bacteria

Aims: To investigate the action of different polyphenolic compounds, extracted from red wine, grape marc and pine bark, on oral bacteria. Methods and Results: The anti-microbial activity of extracts was examined by determining the Minimal Inhibitory Concentration and Minimal Bactericidal Concentration using the macro dilution broth technique. Their effect on the adherence was tested on growing cells of Streptococcus mutans on a glass surface and on a multi-species biofilm grown on saliva-coated hydroxyapatite discs. The effect on glucosyltransferase activity was analysed through the reductions in the overall reaction rate and the quantity of insoluble glucan (ISG) synthesized. Pine bark and grape marc extracts were the most effective inhibitors of the multi-species biofilm formation and of the ISG synthesis. Conclusion: The tested components showed an interesting anti-plaque activity in vitro. Significance and Impact of the Study: This is, to our knowledge, the first and the most complete report on the properties of wine and pine bark extracts that could be used for oral disease prevention purpose.     

The antimicrobial activity of heyneanol A extracted from the root of Taiwanese wild grape

Aims:  To search for antimicrobial compounds against pathogenic bacteria from grape vines ( Vitis spp.). To investigate the antimicrobial efficacy of active compounds towards methicillin-resistant Staphylococcus aureus (MRSA).
Methods and Results:  The root extracts of taiwanese wild grape ( Vitis thunbergii var. taiwaniana ) showed marked activities against Gram-positive bacteria using the disc diffusion method. After purification, the active compound 1 was confirmed as heyneanol A by mass spectroscopy and nuclear magnetic resonance. Heyneanol A showed an minimum inhibitory concentration (MIC) value of 2  μ g ml⁻¹ towards MRSA and a value of 2 to 4  μ g ml⁻¹ for Enterococcus faecium , S. aureus , Streptococcus agalactiae and Streptococcus pyogenes . In addition, the contents of heyneanol A were determined as 36 mg g⁻¹ in roots of taiwanese wild grape.
Conclusions:  The root extracts of grapevines have good antimicrobial activities towards some strains of Gram-positive pathogens. Heyneanol A, the major antimicrobial compound, is especially active towards MRSA. In addition, the abundances of heyneanol A and other stilbenes in the roots of grapevines make it possible to produce natural antimicrobial compounds from this plant species.
Significance and Impact of the Study:  This study reports for the first time the antimicrobial compounds in the root extracts of grapevines. The results will have clinical significance owing to their activities against MRSA.     

Antibacterial activity of naringin derivatives against pathogenic strains

Aims: To study the antimicrobial activity of naringin (NAR), a flavonoid extracted from citrus industry waste, and NAR derivatives [naringenin (NGE), prunin and alkyl prunin esters] against pathogenic bacteria such as L. monocytogenes, E. coli O157:H7 and S. aureus. The relationship between the structure of the chemical compounds and their antagonistic effect was also analysed. Methods and Results: The agar dilution technique and direct contact assaying were applied. NGE, prunin and NAR showed no antimicrobial activity at a concentration of 0·25 mmol l^?1. Similarly, fatty acids with a chain length between C2 and C18 showed no antimicrobial activity at the same concentration. However, prunin‐6″‐O‐acyl esters presented high antibacterial activity, mainly against Gram‐positive strains. This activity increased with increasing chain length (up to 10–12 carbon atoms). Alkyl prunin esters with 10–12 carbon atoms diminished viability of L. monocytogenes by about 3 log orders and S. aureus by 6 log orders after 2 h of contact at 37°C and at a concentration of 0·25 mmol l^?1. The compounds examined were not effective against any of the Gram‐negative strains assayed, even at the highest concentration. Conclusions: Addition of sugars to the aglycone did not enhance its antimicrobial activity. Attachment of a saturated aliphatic chain with 10–12 carbon atoms to the A ring of the flavonoid (or to sugars attached to this ring), seems to be the most promising modification. In conclusion, alkyl prunin esters with a chain length of C10–C12 have promising features as antimicrobial agents because of their high antilisterial and antistaphylococcal activity. Significance and Impact of the Study: This study shows that it is possible to obtain NAR derivatives with important antimicrobial activity, especially against Gram‐positive pathogenic bacteria. It also provides guidelines on the structural modifications in similar molecules to enhance the antimicrobial activity.     

Antibacterial spectrum and cytotoxic activities of serrulatane compounds from the Australian medicinal plant Eremophila neglecta

Aims: To determine the antibacterial spectrum and cytotoxic activities of serrulatane compounds from the Australian plant Eremophila neglecta. Methods and Results: Antimicrobial activities of serrulatane compounds 8,19‐dihydroxyserrulat‐14‐ene ( 1 ) and 8‐hydroxyserrulat‐14‐en‐19‐oic acid ( 2 ) were tested against Gram‐negative and Gram‐positive bacteria including human and veterinary pathogens and some multidrug‐resistant isolates. Minimum inhibitory concentrations (MICs) and minimum bactericidal concentrations (MBCs) of the compounds were determined by broth microdilution assay. Both compounds exhibited antibacterial activity against all Gram‐positive test strains. They showed antimycobacterial activity against isolates of Mycobacterium fortuitum and Mycobacterium chelonae. Of the five Gram‐negative bacteria tested, only Moraxella catarrhalis showed susceptibility to the compounds. Cytotoxic activities were tested in the Vero cell line. Compound 1 showed more activity than 2 in both antibacterial and cytotoxicity assays with cytotoxicity at concentrations similar to the MBC. Conclusions: Serrulatane compounds showed significant activity against medically important bacteria, with 1 exhibiting stronger antibacterial activity. However, they also displayed toxicity to mammalian cells. Significance and Impact of the Study: Serrulatanes are of interest as novel antibacterial compounds for use in biomedical applications; this study reports data obtained with a range of bacterial strains and mammalian cells, essential for assessing the capabilities and limitations of potential applicability of these compounds.     

Antimicrobial potential of polyphenols extracted from almond skins

Aims: To evaluate the antimicrobial properties of flavonoid‐rich fractions derived from natural and blanched almond skins, the latter being a by‐product from the almond processing industry. Methods and Results: Almond skin extracts were tested against Gram‐negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, Serratia marcescens), Gram‐positive bacteria (Listeria monocytogenes, Enterococcus hirae, Staphylococcus aureus, Enterococcus durans) and the yeast Candida albicans. Almond skin fractions were found to have antimicrobial activity against L. monocytogenes and Staph. aureus in the range 250–500 μg ml^?1, natural skins showing antimicrobial potential against the Gram‐negative Salm. enterica. The interactions between three almond skin flavonoids were also evaluated with isobolograms. Conclusions: Pairwise combinations of protocatechuic acid, naringenin and epicatechin showed both synergistic and indifferent interactions against Salm. enterica and Staph. aureus. Antagonism was observed against L. monocytogenes with all combinations tested. Further studies need to be performed to understand the mechanisms responsible for these interactions. Significance and Impact of the Study: Almond skins are a potential source of natural antimicrobials.     

Characterization of α‐rhamnosidase activity from a Patagonian Pichia guilliermondii wine strain

Aims: The purpose of this study was to characterize the α‐l ‐rhamnosidase of Pichia guilliermondii NPCC1053 indigenous wine strain from North‐Patagonian region. Methods and Results: The optimization of yeast culture conditions was carried out and the effects of oenological parameters on α‐l ‐rhamnosidase activity were evaluated. Additionally, the effect of direct contact with must and wine on α‐l ‐rhamnosidase activity was assayed. This strain showed an intracellular inducible α‐l ‐rhamnosidase activity. This enzyme was active at pH, glucose and SO₂ concentrations usually found at the beginning of the fermentation as well as retained high levels of activity after 24 h of incubation in must. Furthermore, P. guilliermondiiα‐l ‐rhamnosidase was able to release monoterpenols and alcohols from grape glycosidic extracts. Conclusions: The α‐l ‐rhamnosidase belonging to P. guilliermondii indigenous wine yeast strain showed mainly an intracellular location and evidenced interesting oenological characteristics. Significance and Impact of the Study: This study contributes to the knowledge of α‐l ‐rhamnosidases from yeast origin because at present, there are few reports about this enzymatic activity in these micro‐organisms. In addition, this work is relevant to the regional wine industry considering that this enzyme could be used in the production of more aromatic young wines.     

Phytochemical, antimicrobial, antioxidant and antigenotoxic potentials of Cyperus rotundus extracts

The aqueous, ethyl acetate, methanolic and Total Oligomer Flavonoids (TOF) enriched extracts, obtained from the aerial parts of Cyperus rotundus, were investigated for their contents in phenolic compounds. Antioxidative activity using the NBT/riboflavin assay system, antimicrobial activity against Gram positive and Gram negative bacterial reference strains as well as antigenotoxic activity tested with the SOS chromotest assay were also studied. Significant antibacterial activity against reference strains; Staphylococcus aureus, Enterococcus faecalis, Salmonella enteritidis and Salmonella typhimurium, was detected in the presence of ethyl acetate and TOF enriched extracts. In addition to their antimicrobial activity, the same extracts showed a significant ability to inhibit nitroblue tetrazolium reduction by the superoxide radical in a non enzymatic O₂^.− generating system, and were also able to reduce significantly the genotoxicity induced by nifuroxazide and Aflatoxin B1. The antioxidant, antimicrobial and antigenotoxic activities exhibited by C. rotundus depend on the chemical composition of the tested extracts.     

Antimicrobial potential of a lipopeptide biosurfactant derived from a marine Bacillus circulans

Aims: To isolate the biologically active fraction of the lipopeptide biosurfactant produced by a marine Bacillus circulans and study its antimicrobial potentials. Methods and Results: The marine isolate B. circulans was cultivated in glucose mineral salts medium and the crude biosurfactant was isolated by chemical isolation method. The crude biosurfactants were solvent extracted with methanol and the methanol extract was subjected to reverse phase high‐performance liquid chromatography (HPLC). The crude biosurfactants resolved into six major fractions in HPLC. The sixth HPLC fraction eluting at a retention time of 27·3 min showed the maximum surface tension‐reducing property and reduced the surface tension of water from 72 mNm^?1 to 28 mNm^?1. Only this fraction was found to posses bioactivity and showed a pronounced antimicrobial action against a panel of Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic micro‐organisms including a few multidrug‐resistant (MDR) pathogenic clinical isolates. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of this antimicrobial fraction of the biosurfactant were determined for these test organisms. The biosurfactant was found to be active against Gram‐negative bacteria such as Proteus vulgaris and Alcaligens faecalis at a concentration as low as 10 μg ml^?1. The biosurfactant was also active against methicillin‐resistant Staphylococcus aureus (MRSA) and other MDR pathogenic strains. The chemical identity of this bioactive biosurfactant fraction was determined by post chromatographic detection using thin layer chromatography (TLC) and also by Fourier transform infrared (FTIR) spectroscopy. The antimicrobial HPLC fraction resolved as a single spot on TLC and showed positive reaction with ninhydrin, iodine and rhodamine‐B reagents, indicating its lipopeptide nature. IR absorption by this fraction also showed similar and overlapping patterns with that of other lipopeptide biosurfactants such as surfactin and lichenysin, proving this biosurfactant fraction to be a lipopeptide. The biosurfactant did not show any haemolytic activity when tested on blood agar plates, unlike the lipopeptide biosurfactant surfactin produced by Bacillus subtilis. Conclusions: The biosurfactant produced by marine B. circulans had a potent antimicrobial activity against Gram‐positive and Gram‐negative pathogenic and semi‐pathogenic microbial strains including MDR strains. Only one of the HPLC fractions of the crude biosurfactants was responsible for its antimicrobial action. The antimicrobial lipopeptide biosurfactant fraction was also found to be nonhaemolytic in nature. Significance and impact of the study: This work presents a nonhaemolytic lipopeptide biosurfactant produced by a marine micro‐organism possessing a pronounced antimicrobial action against a wide range of bacteria. There is a high demand for new antimicrobial agents because of the increased resistance shown by pathogenic micro‐organisms against the existing antimicrobial drugs. This study provides an insight into the search of new bioactive molecules from marine micro‐organisms.     

Bioactive stilbenes from a Bacillus sp. N strain associated with a novel rhabditid entomopathogenic nematode

Aims: The aim of the present study was to purify and characterize a natural antimicrobial compound from Bacillus sp. strain N associated with a novel rhabditid entomopathogenic nematode. Methods and Results: The cell‐free culture filtrate of a bacterium associated with a novel entomopathogenic nematode (EPN), Rhabditis (Oscheius) sp. exhibited strong antimicrobial activity. The ethyl acetate extract of the bacterial culture filtrate was purified by column chromatography, and two bioactive compounds were isolated and their chemical structures were established based on spectral analysis. The compounds were identified as 3,4′,5‐trihydroxystilbene (1) and 3,5‐dihydroxy‐4‐isopropylstilbene (2). The presence of 3,4′,5‐trihydroxystilbene (resveratrol) is reported for the first time in bacteria. Compound 1 showed antibacterial activity against all the four test bacteria, whereas compound 2 was effective against the Gram‐positive bacteria only. Compounds 1 and 2 were active against all the five fungi tested and are more effective than bavistin, the standard fungicide. The antifungal activity of the compounds against the plant pathogenic fungi, Rhizoctonia solani is reported for the first time. Conclusions: Cell‐free extract of the bacterium and isolated stilbenes demonstrated high antibacterial activity against bacteria and fungi especially against plant pathogenic fungi. We conclude that the bacterium‐associated EPN are promising sources of natural bioactive secondary metabolites. Significance and Impact of the Study: Stilbene compounds can be used for the control of fungi and bacteria.     

Modifications on amphiphilicity and cationicity of unnatural amino acid containing peptides for the improvement of antimicrobial activity against pathogenic bacteria

The widespread natural sources‐derived cationic peptides have been reported to reveal bacterial killing and/or growth‐inhibiting properties. Correspondingly, a number of artificial peptides have been designed to understand antibacterial mechanism of the cationic peptides. These peptides are expected to be an alternative antibiotic against drug‐resistant pathogenic bacteria because major antimicrobial mechanism of cationic peptides involves bacterial membrane disorder, although those availabilities have not been well evaluated. In this study, cationic peptides containing Aib were prepared to evaluate the availability as an antimicrobial agent, especially against representative pathogenic bacteria. Among them, BRBA20, consisting of five repeated Aib‐Arg‐Aib‐Ala sequences, showed strong antibacterial activity against both Gram‐negative and Gram‐positive bacteria, including methicillin‐resistant Staphylococcus aureus. Additionally, growth of Serratia marcescens and multidrug‐resistant Pseudomonas aeruginosa, known as proteases‐secreting pathogenic bacteria, were also completely inhibited by BRBA20 under 20 µg/ml peptide concentrations. Our results suggested availabilities of Aib‐derived amphiphilicity and protease resistance in the design of artificial antimicrobial peptides. Comparing BRBA20 with BKBA20, it was also concluded that Arg residue is the preferred cationic source than Lys for antimicrobial action of amphiphilic helices. Copyright © 2010 European Peptide Society and John Wiley & Sons, Ltd.     

Influence of hydrogen peroxide foliar applications on in vitro antimicrobial activity in Capsicum chinense Jacq.

The aim of this study was to evaluate the effect of foliar applications of hydrogen peroxide on the antimicrobial activity of Capsicum chinense Jacq. methanolic extracts. The effects of hydrogen peroxide application on metabolites accumulation of C. chinense var. Jaguar and var. Chichen Itza were evaluated. Total flavonoid and phenolic contents, as well as HPLC quantification of capsaicin and dihidrocapsaicin were carried out. Methanolic extracts were microbiologically tested against Staphylococcus aureus, Escherichia coli, Streptococcus mutants, Salmonella thompson, Listeria monocytogenes, Streptococcus faecalis, and Candida albicans. Total phenolics, flavonoids, and capsaicinoids contents in both varieties treated with hydrogen peroxide were found significantly higher as compared to control. The antibacterial activity of chili extracts was observed against Gram-positive and Gram-negative bacteria as well as anti-yeast. The results of in vitro antibacterial activity showed that hydrogen peroxide application increases the inhibitory effect against the pathogenic micro-organisms. Methanolic extracts of var. Jaguar, were the most active against S. aureus, S. Thompson, and C. albicans, while var. Chichen Itza was most potent against E. faecalis and E. coli. Thus, this study confirmed that metabolite-induced factors (MIFs) as hydrogen peroxide, increased secondary metabolites accumulation in C. chinense methanolic extracts and augmented their antimicrobial activity.