Antimicrobial activity of tea as affected by the degree of fermentation and manufacturing season

Eco-physiological response of secondary metabolites of teas: Review of quality attributes of herbal tea

Herbal tea is a rich source of secondary metabolites which are reputed to have medicinal and nutritional efficacy. These secondary metabolites are influenced by the abiotic and biotic stresses that improve the production of herbal teas in terms of biomass production, accumulation and partitioning of assimilates of compounds. In this study, various examples of herbal teas have been shown to respond differently to secondary metabolites affected by environmental factors. Thus, the meta-analysis of this study confirms that different herbal teas' response to environmental factors depends on the type of species, cultivar, and the degree of shade that the plant is exposed. It is also evident that the metabolic processes are also known to optimize the production of secondary metabolites which can thus be achieved by manipulating agronomic practices on herbal teas. The different phenolic compound in herbal teas possesses the antioxidant, antimicrobial, antiatherosclerosis, anti-inflammatory, antimutagenic, antitumor, antidiabetic and antiviral activities that are important in managing chronic diseases associated with lifestyle. It can be precluded that more studies should be conducted to establish interactive responses of biotic and abiotic environmental factors on quality attributes of herbal teas.

Effects of the Baking Process on the Chemical Composition, Sensory Quality, and Bioactivity of Tieguanyin Oolong Tea

Tieguanyin oolong tea (TOT), a semi-oxidized tea originating from Anxi county in China, is categorized into jade TOT, medium-baked TOT, and deep-baked TOT, based on different baking processes. To study the effects of baking, chemical analysis, sensory evaluation, and bioactivity assessments of the three TOTs were conducted. The results indicated that the baking process promoted the formation of colored macromolecules (e.g., theabrownins), which affected the color of tea infusion. Free amino acids underwent the Maillard reaction and generated specific Maillard reaction products, such as 5-hydroxymethylfurfural and furfural, which modified the taste and aroma. Floral and fresh volatiles were remarkably reduced, while multiple new volatiles were produced, forming a typically baked aroma. The antioxidant activity and antibacterial activity were reduced after baking, which might be associated with the decrease of monomeric catechins. These results provide a scientific basis for understanding the changes caused by the baking process.

Comparative Assessment of the Antibacterial Efficacies and Mechanisms of Different Tea Extracts

Tea is a popular beverage known for its unique taste and vast health benefits. The main components in tea change greatly during different processing methods, which makes teas capable of having different biological activities. We compared the antibacterial activity of four varieties of tea, including green, oolong, black, and Fuzhuan tea. All tea extracts showed antibacterial activity and Gram-positive bacteria (Enterococcus faecalis and Staphylococcus aureus) were more susceptible to tea extracts than Gram-negative bacteria (Escherichia coli and Salmonella typhimurium). Green tea extracts inhibited bacterial pathogens much more effectively in all four varieties of tea with the minimum inhibitory concentration (MIC) values at 20 mg/mL, 10 mg/mL, 35 mg/mL, and 16 mg/mL for E. faecalis, S. aureus, E. coli, and S. typhimurium, respectively. Catechins should be considered as the main antibiotic components of the four tea extracts. Total catechins were extracted from green tea and evaluated their antibacterial activity. Additional studies showed that the catechins damaged the cell membrane and increased cell membrane permeability, leading to changes in the relative electrical conductivity and the release of certain components into the cytoplasm. Tea extracts, especially green tea extracts, should be considered as safe antibacterial food additives.

Survival of Salmonella and Shiga Toxin-Producing Escherichia coli and Changes in Indigenous Microbiota during Fermentation of Home-Brewed Kombucha

ABSTRACT

Survival and growth of Salmonella and Shiga toxin-producing Escherichia coli (STEC) were investigated in kombucha prepared from four brands of commercially available kombucha kits intended for use by home brewers. Changes in populations of the indigenous microbiota responsible for fermentation of kombucha were also determined. An initial population of Salmonella (6.77 log CFU/mL) decreased to below the detection limit (0.30 log CFU/mL) within 10 days in kombucha prepared from two of the test brands. Populations of 1.85 and 1.20 log CFU/mL were detected in two brands fermented for 14 days. An initial STEC population of 7.02 log CFU/mL decreased to <0.30 log CFU/mL in two brands within 14 days; 0.77 and 0.87 log CFU/mL were detected in kombucha prepared from the other two brands. Salmonella and STEC increased within 1 day in three brands of base tea used to prepare kombucha and were stable throughout 14 days of incubation. Both pathogens steadily declined in base tea prepared from one brand of kombucha kit. Inactivation of the pathogens occurred as the pH of the kombucha decreased, but a clear correlation between rates of inactivation among different brands of kits and decrease in pH was not evident. Growth and peak populations of mesophilic aerobic microorganisms, yeasts, lactic acid bacteria, and acetic acid bacteria varied depending on the kombucha kit brand. No strong evidence was found of a correlation between the behavior of Salmonella or STEC and that of any of these groups of indigenous microbiota. Results of this study show that survival of Salmonella and STEC in kombucha and base tea used to prepare kombucha is dependent on inherent differences in commercially available kombucha kits intended for use in home settings. Strict application of hygienic practices is essential for preventing contamination with Salmonella or STEC and reducing the risk of illness associated the consumption of kombucha.

HIGHLIGHTS

Antileishmanial Activity of Lignans, Neolignans, and Other Plant Phenols

Secondary metabolites (SM) from organisms have served medicinal chemists over the past two centuries as an almost inexhaustible pool of new drugs, drug-like skeletons, and chemical probes that have been used in the "hunt" for new biologically active molecules with a "beneficial effect on human mind and body." Several secondary metabolites, or their derivatives, have been found to be the answer in the quest to search for new approaches to treat or even eradicate many types of diseases that oppress humanity. A special place among SM is occupied by lignans and neolignans. These phenolic compounds are generated biosynthetically via radical coupling of two phenylpropanoid monomers, and are known for their multitarget activity and low toxicity. The disadvantage of the relatively low specificity of phenylpropanoid-based SM turns into an advantage when structural modifications of these skeletons are made. Indeed, phenylpropanoid-based SM previously have proven to offer great potential as a starting point in drug development. Compounds such as Warfarin^® (a coumarin-based anticoagulant) as well as etoposide and teniposide (podophyllotoxin-based anticancer drugs) are just a few examples. At the beginning of the third decade of the twenty-first century, the call for the treatment of more than a dozen rare or previously "neglected" diseases remains for various reasons unanswered. Leishmaniasis, a neglected disease that desperately needs new ways of treatment, is just one of these. This disease is caused by more than 20 leishmanial parasites that are pathogenic to humans and are spread by as many as 800 sandfly species across subtropical areas of the world. With continuing climate changes, the presence of Leishmania parasites and therefore leishmaniasis, the disease caused by these parasites, is spreading from previous locations to new areas. Thus, leishmaniasis is affecting each year a larger proportion of the world's population. The choice of appropriate leishmaniasis treatment depends on the severity of the disease and its form of manifestation. The success of current drug therapy is often limited, due in most cases to requiring long hospitalization periods (weeks to months) and the toxicity (side effects) of administered drugs, in addition to the increasing resistance of the parasites to treatment. It is thus important to develop new drugs and treatments that are less toxic, can overcome drug resistance, and require shorter periods of treatment. These aspects are especially important for the populations of developing countries. It was reported that several phenylpropanoid-based secondary metabolites manifest interesting antileishmanial activities and are used by various indigenous people to treat leishmaniasis. In this chapter, the authors shed some light on the various biological activities of phenylpropanoid natural products, with the main focus being on their possible applications in the context of antileishmanial treatment.

Comparison of antimicrobial efficacy of aqueous ozone, green tea, and normal saline as irrigants in pulpectomy procedures of primary teeth

AIM

Sodium hypochlorite, though considered an ideal root canal irrigant, cannot be used at required concentrations in children, due to its undesirable effects. Hence, it is imperative to search for an ideal root canal irrigant to avoid these undesirable effects which we hope to achieve with this study. The antimicrobial efficacy of aqueous ozone, green tea, and normal saline as irrigants in pulpectomy procedures of the primary teeth has been compared.

MATERIALS AND METHODS

Sixty patients between 4 and 8 years of age with a single-rooted deciduous tooth indicated for pulpectomy were included. The infected teeth were randomly allocated to one of the three treatment groups based on the irrigating agents used, namely normal saline, green tea extract, or ozonated water. Specimens for anaerobic culture were collected three times from the teeth: before irrigation, after initial irrigation, and on the 3^rd day after final irrigation.

RESULTS AND CONCLUSION

Mean colony forming unit (CFU) count after both initial and final irrigation with ozonated water was significantly lower when compared with green tea and normal saline. Further, it was observed that the mean CFU count with green tea was significantly lower than the counts obtained with normal saline on the 3^rd day after final irrigation. Hence, both ozonated water and green tea could be considered a good alternative to conventional root canal irrigants in the primary teeth. Larger sample sizes with a larger variety of irrigants are recommended.

Green tea extract and black tea extract differentially influence cecal levels of short-chain fatty acids in rats

Increasing evidence indicates that gut microbiota plays a critical role to maintain the host's health. The biological function of microbially produced short-chain fatty acids (SCFA) becomes the focus of attention. This study aimed to compare the effects of green tea extract (GTE) and black tea extract (BTE) on cecal levels of SCFA in rats. Rats consumed an assigned diet of either a control diet, a GTE diet (10 g/kg), or a BTE diet (10 g/kg), for 3 weeks. The dietary addition of GTE significantly reduced the concentrations of acetate and butyrate in cecal digesta compared to the control, but BTE showed an increased trend for a cecal pool. In the GTE group, a significant amount of undigested starch was excreted in feces, but BTE produced no effect. Interestingly, feces of rats fed the BTE diet contained higher bacterial 16S rRNA gene copy numbers for total eubacteria compared to the control diet. Taken together, treatments of the diets with GTE and BTE brought about a different degree of producing SCFA in rat cecum. BTE might advantageously stimulate more SCFA production than GTE by facilitating bacterial utilization of starch.

Antimicrobial Properties of Teas and Their Extracts in vitro

Tea has recently received the attention of pharmaceutical and scientific communities due to the plethora of natural therapeutic compounds. As a result, numerous researches have been published in a bid to validate their biological activity. Moreover, major attention has been drawn to antimicrobial activities of tea. Being rich in phenolic compounds, tea has the preventive potential for colon, esophageal, and lung cancers, as well as urinary infections and dental caries, among others. The venture of this review was to illustrate the emerging findings on the antimicrobial properties of different teas and tea extracts, which have been obtained from several in vitro studies investigating the effects of these extracts against different microorganisms. Resistance to antimicrobial agents has become an increasingly important and urgent global problem. The extracts of tea origin as antimicrobial agents with new mechanisms of resistance would serve an alternative way of antimicrobial chemotherapy targeting the inhibition of microbial growth and the spread of antibiotic resistance with potential use in pharmaceutical, cosmetic, and food industries.

Fermented foods: patented approaches and formulations for nutritional supplementation and health promotion

Fermentation has had a long history in human food production and consumption. Fermented foods and beverages can comprise anywhere between 5-40% of the human diet in some populations. Not only is this process beneficial for extending shelf-life for foods and beverages, but also fermentation can enhance nutritional properties in a safe and effective manner. In many developed countries, traditional methods are now replaced with specific technologies for production of fermented foods, and an emerging industrial practice allows for higher quality standardization of food products in the market place. Due to changes in fermentation processes and the increased consumption of these products, a detailed review of recent patents involving fermented foods and beverages and their impact on health is warranted. Fermented food products that can enhance nutrition, improve health, and prevent disease on a global level will require consistent fermentation methods, evaluation of nutritional compositions, and food safety testing. This review is intended to guide the development of fermented foods for enhanced human health benefits and suggests the need for multidisciplinary collaborations and structural analysis across the fields of food science, microbiology, human nutrition, and biomedical sciences.

Simultaneous determination of seven bioactive components in Oolong tea Camellia sinensis: quality control by chemical composition and HPLC fingerprints

A simple and reliable method of high-performance liquid chromatography (HPLC) was developed for the quality control of oolong tea (the dry leaves of Camellia sinensis ): the quality control included the HPLC fingerprint and the quantitative determination of seven bioactive compounds chemicals, namely, (-)-gallocatechin, (-)-epigallocatechin, (-)-epigallocatechin gallate, caffeine, (-)-epicatechin, gallocatechin gallate, and (-)-epicatechin gallate. The developed analyses of the chemicals excelled in quantifying the chemicals in oolong tea. The chemical fingerprint of oolong tea was established using the raw materials of three main production sites in China, that is, Fujian (southern and northern parts), Taiwan, and Guangdong. The fingerprints from different cultivated sources were analyzed by hierarchical cluster analysis, similarity analysis, principal component analysis (PCA), analysis of variance (ANOVA), and discriminant analysis. The results indicated that the combination of chromatographic fingerprint and quantification analysEs could be used for the quality assessment of oolong tea and its derived products.

Enhancement of antimicrobial activities of whole and sub-fractionated white tea by addition of copper (II) sulphate and vitamin C against Staphylococcus aureus; a mechanistic approach

BACKGROUND

Enhancement of antimicrobial plant products e.g. pomegranate extract by copper (II) sulphate is known. Such combinations have applications in various settings, including the identification of novel compositions to study, treat and control infection.

METHODS

A combination of white tea (WT) (made allowing 10 minutes infusion time at 100°C) was combined with 4.8 mM copper (II) sulphate and tested for antimicrobial effect on the viability of Staphylococcus aureus NCTC 06571. Comparisons were made with green (GT) and black (BT) teas. A WT sub-fraction (WTF < 1000 Da) was tested with copper (II) sulphate and 4.8 mM vitamin C. pH measurements of samples were taken for controls and to observe any changes due to tea/agent interaction. Catalase was used to investigate hydrogen peroxide release. UV-vis. was used to compare WT and WTF.

RESULTS

A 30 minute incubation at room temperature of copper (II) sulphate alone and combined with WT reduced the viability of S. aureus NCTC 06571 by c.a 1 log10 cfu mL-1. GT and BT with copper (II) sulphate negated activity to buffer values. Combined with copper (II) sulphate, vitamin C, WTF and, vitamin C plus WTF all reduced the viability of S. aureus NCTC 06571 by c.a. 3.5 log10 cfu mL-1. Independent experiments showed the results were not due to pH effects. Adding WT or WTF to copper (II) sulphate resulted in increased acidity. Copper (II) sulphate alone and combined with WT required c.a 300 μg mL-1 (final concentration) catalase to restore S. aureus viability, WTF with copper (II) sulphate and added vitamin C required c.a 600 μg mL-1. WT and WTF UV-visible spectra were similar.

CONCLUSIONS

WT showed no efficacy in the combinations tested. WTF was enhanced with copper (II) sulphate and further with vitamin C. WT and WTF increased acidity of copper (II) sulphate possibly via the formation of chemical complexes. The difference in WT/WTF absorbance possibly represented substances less concentrated or absent in WTF. Investigations to establish which WTF component/s and in what proportions additives are most effective against target organisms are warranted.

Antimicrobial activities of tocklai vegetative tea clones

Thirty-one Tocklai vegetative (TV) tea clones contained caffeine and total catechin 44.39 and 227.55 mg/g dry weight of leaves, respectively. The (-)-epigallocatechin gallate (EGCG) was the most abundant (109.60 mg/g) followed by -(-)-epigallocatechin (EGC, 44.54 mg/g), (-)-epicatechin gallate (ECG, 41.74 mg/g), (-)-epicatechin (EC, 27.42 mg/g) and +catechin (4.25 mg/g). Total catechins were highest in TV 20 (509.7 mg/g) and lowest in TV 6 (71.7 mg/g). The tea clones that contain high level of total catechin exhibited the strongest antimicrobial activity. Among caffeine and flavanol compounds, theaflavins (TF) present in black tea possess a similar antimicrobial potency as EC present in fresh leaves, and that the conversion of catechins to TF during fermentation in making black tea tends to alter their antimicrobial activities. The bioactive molecules other than catechins present in tea leaves may also contribute towards antimicrobial activity.

A novel technique for chitosan microparticle preparation using a water/silicone emulsion: green tea model

Many effective methods such as spray drying, coacervation, ionic gelation, solvent evaporation and sieving have been suggested for entrapping bioactive compounds into micro- or nanoparticles. However, those methods still have some limitations owing to high temperature requirement, difficulty in particle harvesting or low entrapment for uncharged molecules. In this study, a novel chitosan microparticle preparation method was developed using water-in-silicone emulsion technique with green tea extract as a model active compound. Chitosan microparticles of diameter <5 μm were obtained from 2% chitosan solution with tripolyphosphate (TPP) solution as the hardening agent. The size and properties of the particles appeared to depend on several parameters such as TPP, emulsifier concentrations and pH. High concentration of emulsifier led to low encapsulation and particle aggregation. Entrapment efficiency of chitosan microparticles was improved with lower pH of the tripolyphosphate solution [59.94 ± 3.97 of epigallocatechin gallate (EGCG)] while slowing release of catechins. Epigallocatechin and epicatechin were released almost completely within 2 h under acidic condition whereas EGCG and epicatechin gallate were slowly released. In neutral condition, release of catechins depended on their molecular stabilities. The stabilities of catechins loaded in chitosan microparticles were varied under various temperatures. The degradation of tea catechins increased with temperature. However, the degradation of tea catechins loaded in chitosan microparticles was less than that of free catechins. Thus, the new technique for preparing chitosan microparticles containing heat-sensitive water soluble green tea extract was successfully developed. The technique is suitable for micro-encapsulation of hydrophilic compounds into chitosan microparticles with the ease of harvesting technique.

Control of Clostridium perfringens spores by green tea leaf extracts during cooling of cooked ground beef, chicken, and pork

We investigated the inhibition of Clostridium perfringens spore germination and outgrowth by two green tea extracts with low (green tea leaf powder [GTL]; 141 mg of total catechins per g of green tea extract) and high (green tea leaf extract [GTE]; 697 mg of total catechins per g of extract) catechin levels during abusive chilling of retail cooked ground beef, chicken, and pork. Green tea extracts were mixed into the thawed beef, chicken, and pork at concentrations of 0.5, 1.0, and 2.0% (wt/ wt), along with a heat-activated (75 degrees C for 20 min) three-strain spore cocktail to obtain a final concentration of approximately 3 log spores per g. Samples (5 g) of the ground beef, chicken, and pork were then vacuum packaged and cooked to 71 degrees C for 1 h in a temperature-controlled water bath. Thereafter, the products were cooled from 54.4 to 7.2 degrees C in 12, 15, 18, or 21 h, resulting in significant increases (P < 0.05) in the germination and outgrowth of C. perfringens populations in the ground beef, chicken, and pork control samples without GTL or GTE. Supplementation with 0.5 to 2% levels of GTL did not inhibit C. perfringens growth from spores. In contrast, the addition of 0.5 to 2% levels of GTE to beef, chicken, and pork resulted in a concentration-and time-dependent inhibition of C. perfringens growth from spores. At a 2% level of GTE, a significant (P < 0.05) inhibition of growth occurred at all chill rates for cooked ground beef, chicken, and pork. These results suggest that widely consumed catechins from green tea can reduce the potential risk of C. perfringens spore germination and outgrowth during abusive cooling from 54.4 to 7.2 degrees C in 12, 15, 18, or 21 h of cooling for ground beef, chicken, and pork.

Overview of antibacterial, antitoxin, antiviral, and antifungal activities of tea flavonoids and teas

Tea leaves produce organic compounds that may be involved in the defense of the plants against invading pathogens including insects, bacteria, fungi, and viruses. These metabolites include polyphenolic compounds, the six so-called catechins, and the methyl-xanthine alkaloids caffeine, theobromine, and theophylline. Postharvest inactivation of phenol oxidases in green tea leaves prevents oxidation of the catechins, whereas postharvest enzyme-catalyzed oxidation (fermentation) of catechins in tea leaves results in the formation of four theaflavins as well as polymeric thearubigins. These substances impart the black color to black teas. Black and partly fermented oolong teas contain both classes of phenolic compounds. A need exists to develop a better understanding of the roles of polyphenolic tea compounds in food and medical microbiology. This overview surveys and interprets our present knowledge of activities of tea flavonoids and teas against foodborne and other pathogenic bacteria, virulent protein toxins produced by some of the bacteria, virulent bacteriophages, pathogenic viruses and fungi. Also covered are synergistic, mechanistic, and bioavailability aspects of the antimicrobial effects. Further research is suggested for each of these categories. The herein described findings are not only of fundamental interest, but also have practical implications for nutrition, food safety, and animal and human health.

In vivo and in vitro effects of tea extracts on enterotoxigenic Escherichia coli-induced intestinal fluid loss in animal models

OBJECTIVES

Enterotoxigenic Escherichia coli (ETEC) infection is a major cause of dehydrating diarrhoea in infants and early-weaned piglets living under subhygienic conditions. We studied the effect of different tea types and subfractions on the intestinal fluid and electrolyte losses involved in ETEC diarrhoea.

MATERIALS AND METHODS

Jejunal segments of anaesthetised piglets were infected with ETEC or ETEC heat-labile toxin (LT) and subsequently perfused for 8 hours with control or tea solutions containing green or black tea extract (BTE) or 3 different BTE subfractions containing small-size, large-size or no phenolics. Changes in intestinal fluid and electrolyte net absorption were measured. To assess the antisecretory effects of tea, BTE was incubated before or after administration of the secretagogue forskolin in rat jejunal tissue placed in Ussing chambers and Cl- secretion measured as changes in short-circuit current (I(SC)).

RESULTS

Enterotoxigenic E. coli infection of piglet jejunal segments significantly reduced net absorption of fluid, Na+ and Cl- and increased net secretion of K+ compared with controls. Perfusion of the ETEC-infected segments with both 3 g/L green tea extract and BTE significantly inhibited these disturbances in fluid and electrolyte balance. The BTE subfraction rich in polymeric phenolics but not the other subfractions improved the fluid and electrolyte balance. Addition of forskolin to rat jejunal tissue induced a significant increase in I(SC). Pretreating but not posttreating the jejunal tissue with BTE inhibited the forskolin-induced increase in I(SC).

CONCLUSIONS

Tea may inhibit net fluid and electrolyte losses involved in secretory diarrhoea from ETEC.

Camellia sinensis: historical perspectives and future prospects

As the source of brewed tea preparations, Camellia sinensis has operated for centuries at the interface of agriculture, politics, and biology. The purpose of this review is to present an inter-disciplinary survey of issues surrounding cultivation, processing, and consumption of the tea plant. Particular attention is given to the biologic effects of tea: first, assessing at the level of human physiology its value as a chemopreventive and chemotherapeutic agent; second, examining effects of production upon local ecosystems, due to resource demands and industrial farming practices. In sum, C. sinensis emerges as a potentially powerful contributor to both public health and economic growth if its role is managed from a prospective, sustainable, and evidence-based vantage.

Analysis of condensed and hydrolysable tannins from commercial plant extracts

High performance liquid chromatography (HPLC)/DAD and MS qualitative and quantitative analyses of polyphenols, hydrolysable and condensed tannins from Pinus maritima L. and tannic acid (TA) extracts were performed using normal and reverse phase. Normal-phase HPLC was more suitable for pine bark (PBE) and tannic acid extracts analysis. The chromatographic profile revealed that P. maritima L. extract was mainly composed by polymeric flavanols (containing from two to seven units) and tannic acid (characterized by a mixture of glucose gallates containing from three to seven units of gallic acid). Concerning their antimycotic properties, P. maritima L. extract exhibited a broad activity towards yeast strains of the genera Candida, Cryptococcus, Filobasidiella, Issatchenkia, Saccharomyces: MICs from 200 to 4000 microg/ml (corresponding to 140-2800 microg/ml of active polyphenols) were determined. Conversely, no activity of tannic acid was observed over the same target microorganisms. Taken into consideration the above results of HPLC analysis and on the basis of the current literature, we may conclude that only 70.2% of polyphenols (recognized as condensed tannins) occurring in P. maritima L. extract can be apparently considered responsible for its antimycotic activity.

In vitro antimycotic activity of some plant extracts towards yeast and yeast-like strains

As part of screening aimed at the selection of novel antimycotic compounds of vegetable origin, leaf extracts of Camellia sinensis L., Cupressus sempervirens L. and Pistacia lentiscus L. and the seed extract of Glycine soja Sieb. et Zucc. were tested against yeast and yeast-like species implicated in human mycoses. Of the extracts only those of C. sinensis (obtained from a commercial preparation of green tea) exhibited broad activity towards Candida glabrata, Clavispora lusitatiae, Cryptococcus laurentii, Filobasidiella neoformans, Issatchenkia orientalis, Saccharomyces cerevisiae and Prototheca wickerhamii strains. MICs ranging from 300 to 4800 microg extract/mL (corresponding to 130-2010 microg/mL total polyphenols) were observed. Concentrations of the C. sinensis extract over 25 000 microg/mL caused a rapid decrease of viable cells of Fil. neoformans and its activity was dose-dependent. Tests carried out using the pure polyphenols present in C. sinensis extract composition, showed that only epicatechin-3-O-gallate (ECG) and epigallocatechin-3-O-gallate (EGCG) possess antimycotic activity.

Antimicrobial properties of phenolic compounds from berries

AIMS

To investigate the antimicrobial properties of phenolic compounds present in Finnish berries against probiotic bacteria and other intestinal bacteria, including pathogenic species.

METHODS AND RESULTS

Antimicrobial activity of pure phenolic compounds representing flavonoids and phenolic acids, and eight extracts from common Finnish berries, was measured against selected Gram-positive and Gram-negative bacterial species, including probiotic bacteria and the intestinal pathogen Salmonella. Antimicrobial activity was screened by an agar diffusion method and bacterial growth was measured in liquid culture as a more accurate assay. Myricetin inhibited the growth of all lactic acid bacteria derived from the human gastrointestinal tract flora but it did not affect the Salmonella strain. In general, berry extracts inhibited the growth of Gram-negative but not Gram-positive bacteria. These variations may reflect differences in cell surface structures between Gram-negative and Gram-positive bacteria. Cloudberry, raspberry and strawberry extracts were strong inhibitors of Salmonella. Sea buckthorn berry and blackcurrant showed the least activity against Gram-negative bacteria.

CONCLUSION

Different bacterial species exhibit different sensitivities towards phenolics.

SIGNIFICANCE AND IMPACT OF THE STUDY

These properties can be utilized in functional food development and in food preservative purposes.