Inhibition of Listeria monocytogenes by oregano, cranberry and sodium lactate combination in broth and cooked ground beef systems and likely mode of action through proline metabolism

Listeria monocytogenes is a food safety challenge in various food systems including fresh and frozen meat and poultry. Natural antimicrobials from plant sources in combination with salts of organic acids have the potential to control L. monocytogenes. In this research the efficiency of water soluble phenolic extracts of oregano and cranberry in combination with sodium lactate was evaluated for control of L .monocytogenes. In both broth and cooked meat studies, the results indicated that the combination of water soluble extracts of oregano and cranberry, at a ratio of 50:50 and a concentration of 750 ppm, with 2% sodium lactate had the best inhibitory effect in the tested strain. Based on the rationale that phenolics in oregano and cranberry behave as proline analogs, the potential recovery of pathogen growth in medium with the best inhibitor concentration and supplemented with 1 mM proline was evaluated. The results indicated that there was a proline-induced growth recovery, pointing to a possible mechanism of action of inhibitors, involving proline metabolism. These results confirm the potential of plant extracts to be antimicrobial, and when combined with sodium lactate, can be used as a nature constituent of multiple-barrier food preservation systems.     

Inhibition of Listeria monocytogenes by Elite Clonal Extracts of Oregano (Origanum vulgare)

Food safety continues to be a major concern for the food industry in recent years. One of the industry's top priorities has been to find alternative ways to preserve their newly developed foods while satisfying the increasing consumer demand to produce safe, all-natural products. In order to achieve this “clean label”, much research has been devoted to the use of effective plant-based antimicrobials, such as those from herbs and spices, to replace chemical preservatives. However, due to the cross-pollination character of herbs and spices, there is a lot of genetic heterogeneity among different batches of the same plant species. This poses a problem for the routine use of plants, and their extracts, as a barrier towards microbial growth. In order to combat this, a unique tissue-culture-based selection strategy was used to isolate an elite phenolic phytochemical-producing clonal line of oregano (Origanum vulgare). Ethanol extracts of this elite clonal line of oregano were then used to study its inhibitory action against Listeria monocytogenes in both broth and meat systems. Thymol and carvacrol, two of the main phenolic constituents of oregano extracts, were also tested in both systems to evaluate their activity against that of the whole oregano extract.

Results indicate that thymol, carvacrol, and the clonal oregano line were all effective in inhibiting the growth of L. monocytogenes in both systems. Approximately 150-200 ppm of pure carvacrol or thymol was needed in order to significantly inhibit the growth of L. monocytogenes in broth, while at least 1200 ppm (corresponding to 27.8 μg phenolics/ml) of the elite clonal oregano extract was needed to do the same. Inconclusive results were obtained when the clonal line was compared to store-brand samples of oregano. In meat systems, 800 ppm of the oregano extract was able to significantly inhibit the growth of the pathogen more so than 800 ppm of carvacrol. A possible explanation for this is that the oregano extract was able to work more effectively at the interface of the lipid and water-soluble portions of the meat than the carvacrol. These results are promising for the food industry since we have now developed an approach for a highly consistent and reliable natural source of antimicrobial activity for future studies.     

SYNERGISM OF CRANBERRY PHENOLICS WITH ELLAGIC ACID AND ROSMARINIC ACID FOR ANTIMUTAGENIC AND DNA PROTECTION FUNCTIONS

Several studies have shown the antimutagenic DNA protective functions of some naturally occurring phenolic phytochemicals. Emerging research also indicates that synergistic functionality of these phytochemicals in whole foods benefits the management of many diseases. Here we have investigated the potential antimutagenic properties of cranberry phenolics, ellagic acid (EA), rosmarinic acid (RA) and their synergistic interactions on enhancing antimutagenic properties in Salmonella typhimurium tester system against mutagens sodium azide and N‐methyl‐N′‐nitro‐N‐nitrosoguanidine. Ability of these phytochemical treatments to protect oxidative damage to DNA was also investigated using the supercoiled DNA strand scission assay. Results showed that EA was most effective in inhibiting the mutations in S. typhimurium system, whereas RA and EA were equally effective in protecting the DNA from oxidative damage. Results also showed that the antimutagenic functionality of cranberry powder (CP) made from juice extracts was significantly enhanced when 30% (w/w) of phenolics in CP was substituted with RA and EA possibly because of synergistic redox modulation that can influence mutagen function. It is also suggested that the synergistic mixture of cranberry phenolics with RA could also be protecting the cell from mutations by modulating DNA repair systems.     

Extracts of Mexican Oregano (<Emphasis Type="Italic">Lippia berlandieri</Emphasis> Schauer) with Antioxidant and Antimicrobial Activity

Antimicrobial activity of fractions obtained from Mexican oregano (Lippia berlandieri Schauer) chloroform extract was tested by growth inhibition against Escherichia coli, Staphylococcus aureus and Bacillus cereus, and antioxidant capacity was tested by inhibition of linoleic acid oxidation. Fractions were obtained by differences in polarity or structure (phenolic and non-phenolic fraction). Gram-positive organisms were more susceptible to Mexican oregano extracts. Fraction 3 (by polarity) and phenolic fractions I, II, III, IV and V were the extracts with higher antimicrobial activity. The non-phenolic fraction had effect against B. cereus. Polarity fraction 5 and phenolic Fraction II had a high antioxidant capacity; a 0.08% concentration of fraction 5 had a similar effect as butylated hydroxytoluene at 0.01% concentration. Fractions of Mexican oregano with different polarity and functional groups had antioxidant and antimicrobial activity and can be used in a variety of applications.     

Inhibition of Staphylococcus aureus by Phenolic Phytochemicals of Selected Clonal Herbs Species of Lamiaceae Family and Likely Mode of Action through Proline Oxidation

Staphylococcus aureus, a Gram-positive organism, is responsible for numerous infections ranging in severity from skin and soft tissue infections to endocarditis and septic arthritis. Further, Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In this study, several single-seed origin clonal lines of herbs from Lamiaceae family were screened for antimicrobial applications against S. aureus. These clonal lines have consistent total phenolic content, phenolic profile and antioxidant activity as opposed to heterogenous phenolic profiles of typical herbal extracts. The clonal extracts of specific herb species were evaluated for anti- S. aureus activity. Water extracts of clonal lemon balm had the highest anti- S. aureus activity followed by clonal extracts of rosemary RoLA, sage, oregano, rosemary Ro-6, rosemary RoK-2 and chocolate mint. The anti- S. aureus activity of the water extracts correlated with gallic acid and caffeic acid content, which in pure form showed high anti- S. aureus activity. Based on the rationale that gallic acid and caffeic acid were likely proline analogs affecting proline oxidation, the countering effect of proline to overcome their anti- S. aureus activity was evaluated. Results indicated proline can overcome the inhibitory effects of gallic acid and caffeic acid. These results point to the likely role of phenolic oxidation via proline dehydrogenase, which could be an important target for inhibition by phenolic phytochemicals behaving as proline analog mimics. This mode of regulation by phenolics at the bacterial proline dehydrogenase in the plasma membrane may be an important antimicrobial defense in plants and has consequences for disruption of critical energy metabolism of invading bacterial pathogen. This rationale could be used to design new antimicrobial strategies against S. aureus and other relevant bacterial pathogens.     

Current Applications and Future Trends of Lactic Acid Bacteria and their Bacteriocins for the Biopreservation of Aquatic Food Products

This review emphasizes the importance of novel biopreservation strategies and their application to ensure seafood quality and safety especially within the context of increasing demand for minimally processed aquatic food products. The paper addresses the major hazards linked to spoilage and pathogenic bacteria found in fresh and processed aquatic foods, mainly ready-to-eat seafood subjected to short-term storage, and the biological strategies that can be used to minimize their growth. This is followed by an overview of current knowledge about the inhibiting bacteriocin-producing lactic acid bacteria isolated from aquatic food products or that is being evaluated for ensuring safety on seafood and seafood products as well as the characteristics of their bacteriocins. The different strategies for the biopreservation of aquatic food products, such as protective cultures or spray drying, and their current and future applications for the preservation of seafood products are also explored. Finally, novel antimicrobial active and intelligent packaging strategies based on antimicrobials film allowing controlled release of bacteriocins to refrigerated aquatic food products are also discussed.     

The impact of strawflower and mistletoe extract on quality properties of rainbow trout fillets

Many plants, including strawflower and mistletoe, contain antioxidants and antimicrobials, which can increase the shelf life of seafood. The main aim of this study was to investigate the effect of mistletoe and strawflower extracts at doses of 0.5% (w/v) on the sensory, chemical and microbiological properties of rainbow trout fillets during 27 days of storage at 2 ± 1 °C. The phenolic compounds in these plants have been studied, but their effects on food quality and storage properties have not been reported. We found that extract of mistletoe did not extend the shelf life of the fillets; however, the strawflower extract show high antimicrobial activity in fish fillets. The shelf life of rainbow trout was 20 days for the control and fish treated with mistletoe extract and 23 days for fish treated with strawflower extract. The antioxidant effect of extracts on fish fillets was weak, whereas strawflower extract had high antimicrobial effect. Peroxide value (PV) and thiobarbituric acid (TBA) values fluctuated during storage periods around main values below 14 meq O₂ kg^?1 and 0.6 MA kg^?1, respectively. Putrescine, cadaverine, spermine, spermidine, serotonin, tyramine and dopamine were main amine, whereas histamine accumulated at low levels (<2 mg per 100 g). Strawflower suppressed biogenic amine accumulation in fish fillets. At the limit of acceptability, total viable count (TVC), Enterobacteriaceae and lactic acid bacteria count remained below 7.6, 6.83 and 8.01 log CFU g^?1, respectively. The results of this study show that ethanol extracts of strawflower improve the shelf life of rainbow trout.     

CLONAL HERBAL EXTRACTS AS ELICITORS OF PHENOLIC SYNTHESIS IN DARK-GERMINATED MUNGBEANS FOR IMPROVING NUTRITIONAL VALUE WITH IMPLICATIONS FOR FOOD SAFETY

Plant phenolics are secondary metabolites that confer beneficial properties to the plants that produce them. Extracts made from plants that produce these phytochemicals are increasingly being recognized for their antimicrobial properties. In this study, we investigated extracts made from high‐phenolics‐producing clonal lines of oregano and thyme for potential as elicitors of phenolic antioxidant production in dark‐germinated mungbean (Vigna radiata,). Mungbean was dark‐germinated under the rationale that any energy stored in the bean seed in the form of starch may potentially be utilized for enhanced phenolics production, since without a light source the dark‐germinated seedling may not stimulate the development of photosynthetic components. Wafer‐based herb extracts showed the greatest ability to stimulate phenolic content in dark‐germinated mungbeans. Three of the oregano extracts were investigated further and showed an ability to stimulate glucose‐6‐phosphate dehydrogenase (G6PDH), guaiacol peroxidase (GPX), and antioxidant activity. These results suggest that the extracts contain an active elicitor that stimulates phenolic antioxidant content, as well as activity of the pentose‐phosphate pathway. In addition, the results of this study suggest that extracts of high‐phenolics‐producing clonal plants may have potential in the food and agriculture industry as seed treatments for preventing bacterial infection in germinating sprouts by stimulating phenolic antioxidant‐producing pathways, as well as for increasing the nutritional value of sprouts for human consumption.     

SOLID-STATE PRODUCTION OF PHENOLIC ANTIOXIDANTS FROM CRANBERRY POMACE BY RHIZOPUS OLIGOSPORUS

Cranberry pomace is a byproduct of the cranberry processing industry that can be targeted for production of value-added phenolic ingredients. Bio-processing of pomace by solid state fermentation (SSF) using food grade fungi provides unique strategies to improve nutraceutical properties and to produce functional phenolic ingredients. Several functional phenolic phytochemicals exist as glycosides or as other conjugated forms with reduced biological activity. We hypothesize that during SSF the fungal glycosidases mobilize some phenolic antioxidants in cranberry pomace and their activity by hydrolysis via β-glucosidase and releasing the aglycone. To develop this strategy we used food grade fungus Rhizopus oligosporus. Our goal was to target the release of simple phenolic aglycones and mobilized diphenyls. SSF of cranberry pomace was done for 16 days with nitrogen sources, ammonium nitrate (NH₄NO₃) and fish protein hydrolysate (FPH). The two nitrogen treatments increased water extractable phenolics by 15-26% by day 10 in the pomace. Antioxidant protection factor was highest on day 10 for both nitrogen treatments and was 20-25% higher than control for water extracts and 16.5-19.5% for ethanol extracts. The DPPH radical inhibition (DRI) capacity increased by 5% only for the NH₄NO₃ treatment and gradually decreased for FPH treatment in water extracts. There was no significant change in DRI of the ethanol extracts. The β-glucosidase activity increased by 60-fold for NH₄NO3 treatment and by over 100-fold for FPH treatment and correlated well with the increase in the extractable phenolics and antioxidant activity. Changes in diphenyl profiles during the solid-state process analyzed using HPLC indicated that ellagic acid increased by 4-5 fold in water extracts for both the nitrogen treatments. This increase was between 15-27% in the ethanol extracts. We conclude that SSF of cranberry pomace increased the antioxidant activity concurrent with increased β-glucosidase activity. The HPLC profile showed ellagic acid, a compound with anti-carcinogenic properties was enriched. The antioxidant function has implications for prevention of major oxidation-linked diseases such as cancer and CVD. This value-added SSF strategy is an innovative approach to enhance nutraceutically-relevant functional phytochemicals for food and feed applications.     

CRANBERRY PHENOLICS-MEDIATED ELICITATION OF ANTIOXIDANT ENZYME RESPONSE IN FAVA BEAN (VICIA FABA) SPROUTS

The antioxidant response mechanism by which phenolic phytochemicals show their positive benefits in plants and animals is not very well understood. The ability of cranberry juice powder (CP), ellagic acid (EA), rosmarinic acid (RA) and their synergies to elicit a phenolic response in germinating fava bean was investigated. Results indicated that elicitation with CP, EA, RA and their synergies resulted in increased endogenous phenolic synthesis linked to the stimulation of pentose phosphate pathway (PPP). Further, the stimulation of PPP was linked to the accumulation of free proline, suggesting a possible coupling of proline biosynthesis with PPP. Elicitation also resulted in the stimulation of guaiaicol peroxidase, suggesting a possible involvement in modulating structural development of the germinating sprout. Exogenous phenolic elicitation also resulted in the formation of malondialdehyde, which was gradually reduced because of the activation of antioxidant enzyme systems superoxide dismutase and catalase. The results indicate that the possible mode of action of exogenous phenolic phytochemicals in dark germinating fava bean could be by stimulating the PPP linked to proline biosynthesis and by the activation of the antioxidant enzyme system. The results also suggest that pure exogenous phenolics, EA and RA appeared to be effective when they were present in a cranberry phenolic background, suggesting a possible synergistic mode of action between EA, RA and cranberry phenolics in generating an endogenous fava bean antioxidant enzyme response.     

Inhibition of Staphylococcus aureus by Phenolic Phytochemicals of Selected Clonal Herbs Species of Lamiaceae Family and Likely Mode of Action through Proline Oxidation

Staphylococcus aureus, a Gram-positive organism, is responsible for numerous infections ranging in severity from skin and soft tissue infections to endocarditis and septic arthritis. Further, Staphylococcal food poisoning (SFP) caused by enterotoxigenic staphylococci is one of the main food-borne diseases. In this study, several single-seed origin clonal lines of herbs from Lamiaceae family were screened for antimicrobial applications against S. aureus. These clonal lines have consistent total phenolic content, phenolic profile and antioxidant activity as opposed to heterogenous phenolic profiles of typical herbal extracts. The clonal extracts of specific herb species were evaluated for anti- S. aureus activity. Water extracts of clonal lemon balm had the highest anti- S. aureus activity followed by clonal extracts of rosemary RoLA, sage, oregano, rosemary Ro-6, rosemary RoK-2 and chocolate mint. The anti- S. aureus activity of the water extracts correlated with gallic acid and caffeic acid content, which in pure form showed high anti- S. aureus activity. Based on the rationale that gallic acid and caffeic acid were likely proline analogs affecting proline oxidation, the countering effect of proline to overcome their anti- S. aureus activity was evaluated. Results indicated proline can overcome the inhibitory effects of gallic acid and caffeic acid. These results point to the likely role of phenolic oxidation via proline dehydrogenase, which could be an important target for inhibition by phenolic phytochemicals behaving as proline analog mimics. This mode of regulation by phenolics at the bacterial proline dehydrogenase in the plasma membrane may be an important antimicrobial defense in plants and has consequences for disruption of critical energy metabolism of invading bacterial pathogen. This rationale could be used to design new antimicrobial strategies against S. aureus and other relevant bacterial pathogens.     

Evaluation and improvement of antioxidant and antibacterial activities of supercritical extracts from clove buds

For the first time, extracts from clove buds obtained by supercritical carbon dioxide extraction were screened for antioxidant and antibacterial activities. Additionally, antioxidant and antibacterial activities of extracts obtained by the supercritical extraction of the clove bud–oregano leaf mixtures were studied. Supercritical extract of pure clove had the highest eugenol (64%) and total phenolic content (530.56 mg GAE/g_extract). All extracts had antioxidant activity comparable to synthetic antioxidants against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radicals and formation of peroxides. Presence of 0.6% and 5% of oregano extract in the clove extracts obtained from the clove–oregano plant mixtures improved their antioxidant activity with respect to the extract from pure clove. Clove extract showed moderate antibacterial activities against selected Staphylococcus and Enterococcus bacterial strains. Presence of 50% of the oregano extract improved antibacterial activity of clove extract against all tested strains and resulted in a synergistic antibacterial activity against Methicillin-resistant Staphylococcus haemolyticus strain (MIC ? 1.25 μg/mL). Study demonstrated great potential of supercritical clove extract as natural functional ingredient and the possibility of increasing its antioxidant and antibacterial efficiencies in order to apply lower concentrations and to reduce undesirable flavour notes and toxicological effects in final products.     

Inhibition of Helicobacter pylori by Fermented Milk and Soymilk Using Select Lactic Acid Bacteria and Link to Enrichment of Lactic Acid and Phenolic Content

Ulcer-associated dyspepsia is caused by infection with Helicobacter pylori which is linked to the majority of peptic ulcers. Antibiotic treatment does not always inhibit or kill H. pylori with potential for antibiotic resistance. The objective of this study was to determine the potential of lactic acid bacterial fermented milk and soymilk products to inhibit H. pylori. All fermented product extracts had inhibitory potential, except for Lactobacillus bulgaricus fermented soymilk sample. Further, the addition of cranberry–chitosan oligosaccharide mixture to the fermented substrates did not inhibit the growth of Lactobacillus plantarum (LP2) but further enhanced H. pylori inhibition. The observed H. pylori inhibition was correlated to the increased total phenolic content in the fermented extracts due to cranberry phenolics. These results confirm the potential of lactic acid bacterial fermented milk and soymilk products to inhibit H. pylori. When combined with cranberry phenolics and prebiotic chitosan oligosaccharide, the same lactic acid bacterial fermented extracts can be used as a natural constituent of multiple-barrier system to inhibit ulcer-linked H. pylori.     

Antioxidant properties of tuna-skin and bovine-hide gelatin films induced by the addition of oregano and rosemary extracts

We have investigated the antioxidant properties (FRAP ferric-reducing ability and ABTS radical-scavenging capacity) as well as the light barrier properties of gelatin-based edible films containing oregano or rosemary aqueous extracts. For comparative purposes both bovine-hide and tuna-skin gelatins were studied. The oregano and rosemary extracts were first characterised by both their total phenolic content and antioxidant activity, with the oregano extract showing the higher values. HPLC and confocal laser scanning microscopy revealed qualitative differences between extracts although rosmarinic acid was the most abundant phenolic compound in both. After determining the total quantities of phenolics on films, the polyphenol–protein interaction was found to be more extensive when tuna-skin gelatin was employed. However, this did not clearly affect the antioxidant properties of the films, although it could affect the phenol diffusion from film to food. The light barrier properties were improved by the addition of oregano or rosemary extracts, irrespective of the type of gelatin employed.     

Synergistic effect of thymol and carvacrol combined with chelators and organic acids against Salmonella Typhimurium

To identify synergistic combinations of different food additives, the antimicrobial effects of thymol and carvacrol against Salmonella Typhimurium were assessed alone and in combination with various other preservatives including EDTA, acetic acid, lactic acid, and citric acid. Overall, growth of Salmonella Typhimurium was significantly inhibited in Mueller-Hinton broth containing thymol, carvacrol, EDTA, acetic acid, lactic acid, or citric acid at concentrations of 400 mg/liter, 400 microl/liter, 300 mg/liter, 0.2% (vol/vol), 0.2% (vol/vol), and 0.2% (wt/vol), respectively. The combination of different antimicrobials such as thymol or carvacrol with EDTA, thymol or carvacrol with acetic acid, and thymol or carvacrol with citric acid all resulted in significantly reduced populations of Salmonella Typhimurium. In samples treated with combinations, these antimicrobials had synergistic effects compared with samples treated with thymol, carvacrol, EDTA, acetic acid, or citric acid alone. However, the combined use of lactic acid with thymol or carvacrol did not produce a synergistic effect against Salmonella Typhimurium. Thus, some chelators or organic acids can be used as food preservatives in combination with thymol and carvacrol to reduce the concentrations needed to produce an adequate antimicrobial effect.     

Compositions, antioxidant and antimicrobial activities of Helichrysum (Asteraceae) species collected from Turkey

The methanolic extracts of 16 Helichrysum species were investigated for their in vitro antioxidant, radical scavenging and antimicrobial activities. All the extracts showed strong antioxidant and radical scavenging activity. The highest total antioxidant capacity as ascorbic acid equivalents (AAE) of 194.64 mg/g dry extract was obtained for Helichrysum noeanum in the phosphomolybdenum assay. The highest IC₅₀ value (7.95 μg/ml) was observed for the extract of Helichrysum stoechas subsp. barellieri in the DPPH assay. The total phenolic contents of the extracts ranged from 66.74 to 160.63 mg gallic acid equivalents (GAE)/g dry extract. The major component present in the extracts was identified as chlorogenic acid followed by apigenin-7-glucoside and apigenin by HPLC analysis. All the extracts showed significant antimicrobial activity against microorganisms containing 13 bacteria and two yeasts in the agar diffusion method.     

COMBINATION WITH PLANT EXTRACTS IMPROVES THE INHIBITORY ACTION OF DIVERGICIN M35 AGAINST LISTERIA MONOCYTOGENES

ABSTRACT

The susceptibility of 11 strains of Listeria monocytogenes to divergicin M35, a bacteriocin produced by Carnobacterium divergens strain M35, and to aqueous extracts of garlic, onion, oregano, red chili and black pepper at 30 and 10C, was evaluated using a microdilution assay. The susceptibility of divergicin‐resistant strains to combinations of these agents was also evaluated. Three strains were resistant to divergicin M35 (>500 µg/mL) at 30C but were more susceptible at 10C. Garlic gave the most inhibitory plant extract, followed by onion, while oregano, red chili and black pepper extracts were less active at both temperatures. Garlic extract and divergicin M35 combined or with other extracts increased inhibitory activity against the divergicin‐resistant strains. The garlic/divergicin combination was the most effective at inhibiting these strains and was bactericidal at both temperatures. Log‐phase cells were the most susceptible to the garlic/divergicin combination. Stationary‐phase cells were much more resistant at both incubation temperatures. Furthermore, the effect of the garlic/divergicin combination at inhibiting divergicin‐resistant L. monocytogenes in a food system was also studied using cold‐smoked salmon as a food model. Results indicated that this combination could efficiently reduce the viability of L. monocytogenes in smoked salmon stored at 10C.

PRACTICAL APPLICATIONS

There is increasing popularity worldwide for chemical preservative‐free, ready‐to‐eat and minimally processed seafood with low salt, fat and sugar content. Bacteriocins produced from lactic acid bacteria can have a potential application to prolong the shelf life of cold‐smoked salmon. Also, plant and spice extracts have been shown to contain antibacterial substances with potential for application in foods. Thus, this research explores the combination of divergicin M35, a bacteriocin produced by Carnobacterium divergens strain M35, and aqueous extracts of garlic, onion, oregano, red chili and black pepper to inhibit Listeria monocytogenes and to prolong the shelf life of cold‐smoked salmon.     

Plant location and extraction procedure strongly alter the antimicrobial activity of murta extracts

Leaves and fruits of Murta (Ugni Molinae Turcz.) growing in three locations of Chile with diverse climatic conditions were extracted by using ethanol/water mixtures at different ratios and the antimicrobial activity was assessed. Extracts containing the highest polyphenolic content were from murta plants grown nearer to the mountain (58 mg GAE/g murta), subjected to extreme summer/winter-day/night temperature changes and rainy regime. Extracts from leaves collected in the valley and coast contained 46 and 40 mg GAE/g murta, respectively. A mixture of 50% ethanol/water was the most efficient in extracting polyphenols, showing pure solvents—both water and ethanol—a lower extraction capacity. No correlation between antioxidant capacity and polyphenolic content was found. Extracts from Murta leaves provoked a decrease in the growing of Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus, and showed no activity against the beneficial, probiotic bacteria. A significant correlation between polyphenol content and antimicrobial activity on harmful bacteria was found. Myricetin glucoside and quercetin glucoside/glucuronide/dirhamnoside presumably contributed to the antimicrobial activity of the extract. The higher antimicrobial activity of leaves extracts compared to the fruits could be attributed to flavan-3-ols and other flavonol glycosides. Quercetin glucuronide, myricetin xyloside and flavan-3-ols in polymeric form were tentatively identified for the first time in murta extracts. Both extracts showed an antimicrobial activity similar to some commercial antibiotics, suggesting their suitability to replace synthetic antimicrobials in food.     

INHIBITION OF HELICOBACTER PYLORI BY PHENOLIC EXTRACTS OF SPROUTED PEAS (PISUM SATIVUM L.)

Infection by Helicobacter pylori is associated with gastric and duodenal ulcers. Conventional treatments to eradicate it have side‐effects such as diarrhea and dizziness. The excessive use of antibiotics could also lead to antibiotic‐resistant bacteria. The use of plant phenolic phytochemicals can be an alternative because of their health benefits due to both antioxidant activity and antimicrobial activity. The pea (Pisum sativum), the world's second most important pulse crop, produces phenolic phytochemicals with antimicrobial potential. Because the synthesis of phenolic compounds increases with stress, we investigated the anti‐H. pylori effectiveness of extracts from pea sprouts, germinated in the dark condition following treatment with either distilled water or acetyl salicylic acid. The peas were germinated for 8 days and the sprouted samples were measured for total soluble phenolic content, antioxidant and guaiacol peroxidase activity. Subsequently, the sprout extracts were tested for anti‐H. pylori activity using the agar diffusion method and the effective dose was determined based on phenolic content. The results showed that both acetyl salicylic acid‐treated and untreated pea sprouts at days 5 and 8 had anti‐H. pylori activity. The minimum volume for inhibition was 50 μL of extracts. The inhibitory effects were dose dependent. From this study, the potential to use natural phenolic phytochemicals from pea sprouts to control H. pylori was found to be promising. This provides a strategy and foundation to design legume phenolics as functional ingredients against H. pylori.     

The influence of harvest time on essential oil composition,phenolic constituents and antioxidant properties of Turkish oregano (Origanum onites L.)

BACKGROUND: The aim of this research was to determine essential oil composition, phenolic constituents and antioxidant properties of Turkish oregano (Origanum onites L.) leaves harvested during the months of June to September. RESULT: The maximum essential oil yield in the leaves appeared in the middle of July. The main components of oregano oil were carvacrol, thymol, γ‐terpinene, p‐cymene, α‐terpinene and α‐pinene. Carvacrol was highest in the July harvest. The maximum extract yield was found in September. Oil distilled from early‐season (June) harvested leaves had the highest antioxidant ability, expressed as low concentration providing 50% inhibition of free radical scavenging activity and high levels of reducing/antioxidant capacity. Twelve phenolic compounds of oregano extract were identified and the main components were found to be rosmarinic acid and acecetin. The maximum rosmarinic acid and acecetin were found in harvests of July and June, respectively. Total phenolic contents, free radical scavenging activities and reducing/antioxidant capacities were found to be highest in the July harvest. DISCUSSION: All yields, chemical compositions, free radical scavenging activities and reducing/antioxidant capacities of extracts and essential oils of Turkish oregano changed importantly depending on vegetative periods of growing season. Copyright © 2009 Society of Chemical Industry