An in vitro Study on the DNA Damaging Effects of Phytochemicals Partially Isolated from an Extract of Glinus lotoides

An extract of Glinus lotoides, a medicinal plant used in Africa and Asia for various therapeutic purposes, was recently shown to cause DNA damage in vitro. To further explore the potential genotoxicity of this plant, fractionation of the crude extract was performed using reverse phase solid‐phase extraction and a stepwise gradient elution of methanol in water. Four fractions were collected and subsequently analysed for their DNA damaging effects in mouse lymphoma cells using an alkaline version of the comet assay. To identify potential genotoxic and non‐genotoxic principles, each fraction was then subjected to liquid chromatography coupled to mass spectrometry, LC‐MS/MS. 1D and 2D nuclear magnetic resonance analyses were used to confirm the identity of some saponins. Although fractions containing a mixture of flavonoids and oleanane‐type saponins or oleanane‐type saponins alone produced no DNA damage, those containing hopane‐type saponins exhibited a pronounced DNA damaging effect without affecting the viability of the cells. To conclude, even if this study presents evidence that hopane‐type of saponins are endowed with a DNA damaging ability, further studies are needed before individual saponins can be cited as a culprit for the previously reported genotoxicity of the crude extract of G. lotoides. Copyright © 2012 John Wiley & Sons, Ltd.     

Formula Optimization of the Jiashitang Scar Removal Ointment and Antiinflammatory Compounds Screening by NF‐κB Bioactivity‐guided Dual‐luciferase Reporter Assay System

Inflammation plays a role in scar formation; therefore, decreasing inflammation benefits scar removal. Jiashitang scar removal ointment (JST) is a commercially available traditional Chinese medicinal formulation. It is composed of extracts from Carthamus tinctorius L. (Car), Rheum officinale Baill. (Rhe), Salvia miltiorrhiza Beg. (Sal), and Panax notoginseng (Burk.) F. H. Chen (Pan), which are all herbs with potent antiinflammatory activities. Our aims are to optimize the formula of JST and to elucidate its antiinflammatory active components. Response surface methodology was applied to optimize proportions of the four herb extracts. The antiinflammatory effects were evaluated using in vitro and in vivo models. To screen for active components in this formula, a bioactivity‐based ultra‐performance liquid chromatography/quadrupole time‐of‐flight mass spectrometry analysis was performed. After optimization, the antiinflammatory effects of the new formula were significantly superior to the original one. Screening identified 13 active ingredients: a series of saffiomin, emodin, salvianolic acid, tanshinone, and triterpenoid saponin derivatives. These active ingredients were predicted to exert nuclear factor‐κB inhibiting effects through MAPK, PI3K/AKT, and NIK‐IKK pathways. In conclusion, the original formula was successfully optimized with more potent antiinflammatory activity. These methods can be applied to researches of other formulas. Copyright © 2014 John Wiley & Sons, Ltd.     

Screening of herbal extracts against multi‐drug resistant Acinetobacter baumannii

Antibiotic resistance is increasing resulting in a decreasing number of fully active antimicrobial agents available to treat infections with multi‐drug resistant (MDR) bacteria. Herbal medicines may offer alternative treatment options. A direct inoculation method simulating the standard disc diffusion assay was developed to determine in vitro antimicrobial activity of sixty herbal extracts against MDR‐Acinetobacter baumannii (A. baumannii). Eighteen herbal extracts inhibited MDR‐A. baumannii on agar plates, although the magnitude and quality of bacterial inhibition differed considerably among the antibacterial herbal extracts. Next, minimal inhibitory concentration (MIC) of these antibacterial herbal extracts was calculated using a broth microdilution assay. For most herbal extracts, the larger the zone of inhibition on agar plates, the lower the MIC. In general, hetero‐resistance on agar plates correlated with higher MIC. The skip well phenomenon was seen with two herbal extracts. In conclusion, 30% of the screened herbal extracts demonstrated in vitro antibacterial activity against MDR‐A. baumannii using similar rigorous testing methods as those commonly employed for assessing antimicrobial activity of synthetic antibacterial agents. Characterization of a specific compound conferring this antibacterial activity of the herbal extracts may help to identify novel antimicrobial agents active against highly resistant bacteria. Copyright © 2010 John Wiley & Sons, Ltd.     

Modulation of Cox‐1, 5‐, 12‐ and 15‐Lox by Popular Herbal Remedies Used in Southern Italy Against Psoriasis and Other Skin Diseases

Acanthus mollis (Acanthaceae), Achillea ligustica, Artemisia arborescens and Inula viscosa (Asteraceae) are used in Southern Italy against psoriasis and other skin diseases that occur with an imbalanced production of eicosanoids. We here assessed their in vitro effects upon 5‐, 12‐, 15‐LOX and COX‐1 enzymes as well as NFκB activation in intact cells as their possible therapeutic targets. All methanol crude extracts inhibited both 5‐LOX and COX‐1 activities under 200 µg/mL, without significant effects on the 12‐LOX pathway or any relevant in vitro free radical scavenging activity. NFκB activation was prevented by all extracts but A. mollis. Interestingly, A. ligustica, A. arborescens and A. mollis increased the biosynthesis of 15(S)‐HETE, an anti‐inflammatory eicosanoid. A. ligustica (IC₅₀ = 49.5 µg/mL) was superior to Silybum marianum (IC₅₀ = 147.8 µg/mL), which we used as antipsoriatic herbal medicine of reference. Its n‐hexane, dichloromethane and ethyl acetate fractions had also inhibitory effects on the LTB₄ biosynthesis (IC₅₀s = 9.6, 20.3 and 68 µg/mL, respectively) evidencing that the apolar extracts of A. ligustica are promising active herbal ingredients for future phytotherapeutical products targeting psoriasis. © 2014 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.     

Phenolic‐Linked Biochemical Rationale for the Anti‐Diabetic Properties of Swertia chirayita (Roxb. ex Flem.) Karst.

The crude extract of Swertia chirayita, an important medicinal plant of Nepal, is locally used for many diseases including type 2 diabetes. In this study, crude aqueous and 12% ethanol solution extracts of S. chirayita collected from nine districts of Nepal were analyzed for anti‐diabetic‐linked anti‐hyperglycemia potential using in vitro biochemical assays. There was moderate‐to‐high positive correlation between antioxidant activity and total phenolic content of both extracts and moderate‐to‐high α‐glucosidase inhibitory activity. Although the anti‐diabetic property of S. chirayita is mainly attributed to the phytochemical swerchirin present in its hexane fraction, we propose that the crude extract of this plant used in local healing also has anti‐hyperglycemia potential. The crude extracts indicated the presence of three main phytochemicals mainly mangiferin, swertiamarin, and amarogentin and their derivatives. Among the standard compounds (mangiferin, swertiamarin, and amarogentin), mangiferin showed α‐glucosidase and 2,2‐diphenyl‐1‐picrylhydrazyl radical inhibitory activity indicating anti‐hyperglycemia potential. Copyright © 2012 John Wiley & Sons, Ltd.     

Effects of Penta‐O‐galloyl‐β‐D‐glucose on Human Neutrophil Function: significant Down‐Regulation of L‐selectin Expression

Penta‐O‐galloyl‐β‐D‐glucose (PGG) occurrs in high concentrations in medicinal herbs such as Rhus chinensis, Paeonia suffruticosa, Acer truncatum and Terminalia chebula, which demonstrate anti‐inflammatory activity. We investigated the effect of PGG on stimulated and non‐stimulated neutrophils in processes which included reactive oxygen species generation (ROS), metalloproteinase‐9 and interleukin‐8 secretion (IL‐8), β₂ integrin (CD11b) and L‐selectin (CD62L) expression and apoptosis. In concentrations of 5 μM–20 μM, PGG demonstrated statistically significant inhibition of ROS generation, IL‐8 secretion and β₂ integrin expression in stimulated neutrophils. The inhibition of L‐selectin expression by PGG resulted in prevention in neutrophils’ endothelial attachment. The result obtained may explain the anti‐inflammatory activity of this compound and underline the contribution of PGG in the activity of PGG rich plant extracts. Copyright © 2012 John Wiley & Sons, Ltd.     

In Vitro Inhibition of the Transcription Factor NF‐κB and Cyclooxygenase by Bamboo Extracts

Several bamboo species have been used in traditional medicine for the treatment of inflammatory conditions. The present study evaluates the in vitro anti‐inflammatory properties of the traditionally used bamboo species Phyllostachys nigra (Lodd.) Munro and Sasa veitchii (Carr.) Rehder to explore their future research opportunities and therapeutic potential as anti‐inflammatory agents. The extracts were evaluated for their potential inhibitory activity at the level of NF‐κB‐induced gene expression and suppression of cyclooxygenase (COX)‐1 and COX‐2 enzyme activities, representative pharmacological targets for the anti‐inflammatory action of glucocorticoids and non‐steroidal anti‐inflammatory drugs, respectively. The activity of P. nigra (Lodd.) Munro and S. veitchii (Carr.) Rehder was compared with bamboo species without traditional anti‐inflammatory indications. High‐performance liquid chromatography with diode‐array detection and liquid chromatography–tandem mass spectrometry analyses were performed to phytochemically characterize the extracts. P. nigra (Lodd.) Munro leaf extract potently inhibited NF‐κB‐induced gene expression, while S. veitchii (Carr.) Rehder leaf extract exerted a selective COX‐2 inhibition. The crude extracts consistently showed a more potent bioactivity than the solid phase extraction fractions. P. nigra (Lodd.) Munro and S. veitchii (Carr.) Rehder both exert anti‐inflammatory properties, but act via a different molecular mechanism. Copyright © 2013 John Wiley & Sons, Ltd.     

大鼠肠道菌群对三七总皂苷体外降解的研究

目的探究雌、雄大鼠肠道菌群对三七总皂苷中3种皂苷(三七皂苷R1、人参皂苷Rg1和人参皂苷Rb1)的体外降解作用。方法将三七总皂苷分别与雌、雄大鼠肠道菌群孵育液在厌氧条件下共同培养24 h,测定不同时间点孵育液中3种皂苷的量。结果雌、雄大鼠肠道菌群对人参皂苷Rb1均有降解作用,雄鼠的降解较雌鼠稍快。雌、雄鼠肠道菌群对三七皂苷R1和人参皂苷Rg1均无明显降解作用。结论在离体条件下,三七总皂苷中人参皂苷Rb1会被肠道菌群降解,而三七皂苷R1和人参皂苷Rg1则较为稳定。     

Antiprotozoal,antimycobacterial and cytotoxic potential of twenty‐three British and Irish red algae

As part of our continuing research on seaweeds, we have screened the crude extracts of 23 red marine algae collected from England and Ireland. The clinically important blood‐stage life forms of Trypanosoma brucei rhodesiense, T. cruzi, Leishmania donovani and Mycobacterium tuberculosis were used as test organisms in the in vitro assays. The selectivity of the extracts was determined by using mammalian skeletal myoblast (L6) cells. All algal extracts showed activity against T. brucei rhodesiense, with Corallina officinalis and Ceramium virgatum being the most potent (IC₅₀ values 4.8 and 5.4 μg/ml), whilst none of the algal extracts inhibited the growth of T. cruzi. Except for Porphyra leucosticta, extracts from all seaweeds also showed leishmanicidal activity with IC₅₀ values ranging from 16.5 to 85.6 μg/ml. Only the crude extract of Calliblepharis jubata showed some weak activity against Mycobacterium tuberculosis (MIC value 256 μg/ml), while the others were inactive at this concentration. Corallina officinalis was the only seaweed that displayed some marginal cytotoxicity (IC₅₀ value 88.6 μg/ml), and all remaining extracts were non‐toxic towards L6 cells at 90 μg/ml concentration. To our knowledge, this is the first study reporting antiprotozoal and antimycobacterial activity of British and Irish red algae. Copyright © 2010 John Wiley & Sons, Ltd.     

The leishmanicidal effect of (3S)‐16,17‐didehydrofalcarinol,an oxylipin isolated from Tridax procumbens,is independent of NO production

The in vitro leishmanicidal effect of (3S)‐16,17‐didehydrofalcarinol (1) isolated from Tridax procumbens whole plant against Leishmania mexicana, the causative agent of cutaneous leishmaniasis (chiclero's ulcer) in the New World, was investigated. This oxylipin showed significant in vitro activity against promastigotes and intracellular amastigotes of L. mexicana. Its inhibitory effect on amastigotes was not due to activation of NO in recombinant γ‐interferon‐stimulated macrophages, since the production of NO was decreased in presence of the oxylipin. This is the first report on the leishmanicidal activity against the intracellular stage (amastigote) of the oxylipin (3S)‐16,17‐didehydrofalcarinol. Copyright © 2009 John Wiley & Sons, Ltd.     

Antioxidant,Anti‐inflammatory,and Chemoprotective Properties of Acacia catechu Heartwood Extracts

Aqueous extracts of Acacia catechu heartwood are rich source of catechin and epicatechin (gallic acid derivatives), with smaller amounts of flavonoids. Extracts have also been prepared with ethyl acetate, ethanol, and methanol, and the properties of these extracts have been studied and are reviewed. Potent antioxidant activity has been well established in both in vitro and in vivo studies. This antioxidant activity is believed to be responsible for the anti‐inflammatory, tissue protectant, antineoplastic, and analgesic activities that have been demonstrated and clearly established in animal and cell culture systems. Furthermore, antihyperglycemic, antidiarrheal, antinociceptive, and antipyretic activities have been demonstrated in animal studies. No adverse effects have been observed in animal or human studies or in cell culture systems. In spite of the fact that Acacia products have been used for many years and the general safety of catechins and epicatechins is well documented, few human studies have ever been conducted on the efficacy or safety of A. catechu heartwood extracts. Several studies have shown that a two‐ingredient combination product containing A. catechu extract exhibited no adverse effects when administered daily for up to 12 weeks while exhibiting significant anti‐inflammatory activity in subjects with osteoarthritis of the knee. There is a need for additional human clinical studies with regard to efficacy and safety. © 2015 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.     

Metabolism of the major Echinacea alkylamide N‐isobutyldodeca‐2E,4E,8Z,10Z‐tetraenamide by human recombinant cytochrome P450 enzymes and human liver microsomes

Echinacea preparations are used for the treatment and prevention of upper respiratory tract infections. The phytochemicals believed responsible for the immunomodulatory properties are the alkylamides found in ethanolic extracts, with one of the most abundant being the N‐isobutyldodeca‐2E,4E,8Z,10Z‐tetraenamide (1). In this study, we evaluated the human cytochrome P450 enzymes involved in the metabolism of this alkylamide using recombinant P450s, human liver microsomes and pure synthetic compound. Epoxidation, N‐dealkylation and hydroxylation products were detected, with different relative amounts produced by recombinant P450s and microsomes. The major forms showing activity toward the metabolism of 1 were CYP1A1, CYP1A2 (both producing the same epoxide and N‐dealkylation product), CYP2A13 (producing two epoxides), and CYP2D6 (producing two epoxides and an hydroxylated metabolite). Several other forms showed less activity. In incubations with human liver microsomes and selective inhibitors, CYP2E1 was found to be principally responsible for producing the dominant, hydroxylation product, whereas CYP2C9 was the principal source of the epoxides and CYP1A2 was responsible for the dealkylation product. In summary, in this study the relative impacts of the main human xenobiotic‐metabolizing cytochrome P450s on the metabolism of a major Echinacea alkylamide have been established and the metabolites formed have been identified. Copyright © 2010 John Wiley & Sons, Ltd.     

Antitumor activities of dammarane triterpene saponins from Bacopa monniera

Bioassay‐guided methods were used to test the antitumor activity of methanol extract of the whole plant of Bacopa monniera (L.) Wettst. and four different fractions (petroleum ether, CHCl₃, EtOAc, and n‐BuOH fractions) of the methanol extract. Among the five crude samples, n‐BuOH fraction was noted to have the highest antitumor activity. The dammarane triterpene saponins isolated from n‐BuOH fraction, bacopaside É (1) and bacopaside VII (3), had potential antitumor effect. 1 and 3 showed cytotoxicity of all the tested human tumor cell lines MDA‐MB‐231, SHG‐44, HCT‐8, A‐549 and PC‐3M in MTT assay in vitro, and showed 90.52 % and 84.13 % inhibition in mouse implanted with sarcoma S180 in vivo at the concentration of 50 μmol/kg, respectively. The remaining two compounds, bacopaside II (2) and bacopasaponin C (4) were found to be much less potent compared with 1 and 3. 1 and 3 significantly inhibited human breast cancer cell line MDA‐MB‐231 adhesion, migration and Matrigel invasion in vitro at the concentration of 50 μmol/L. Since no antitumor activities about the monomers from Bacopa monniera (L.) Wettst. have been reported, these results indicate that the mechanism of action of 1 and 3 needs further study. Copyright © 2009 John Wiley & Sons, Ltd.     

ESP‐102, a combined extract of Angelica gigas,Saururus chinensis and Schizandra chinensis,protects against glutamate‐induced toxicity in primary cultures of rat cortical cells

It was reported previously that ESP‐102, a combined extract of Angelica gigas, Saururus chinensis and Schizandra chinensis, significantly improved scopolamine‐induced memory impairment in mice and protected primary cultured rat cortical cells against glutamate‐induced toxicity. To corroborate this effect, the action patterns of ESP‐102 were elucidated using the same in vitro system. ESP‐102 decreased the cellular calcium concentration increased by glutamate, and inhibited the subsequent overproduction of cellular nitric oxide and reactive oxygen species to the level of control cells. It also preserved cellular activities of antioxidative enzymes such as superoxide dismutase, glutathione peroxidase and glutathione reductase reduced in the glutamate‐injured neuronal cells. While a loss of mitochondrial membrane potential was observed in glutamate treated cells, the mitochondrial membrane potential was maintained by ESP‐102. These results support that the actual mechanism of neuroprotective activity of ESP‐102 against glutamate‐induced oxidative stress might be its antioxidative activity. Copyright © 2009 John Wiley & Sons, Ltd.     

Bioactivity‐guided Isolation of Cytotoxic Sesquiterpene Lactones of Gochnatia polymorpha ssp. floccosa

Phytochemical study of Gochnatia polymorpha (Less) Cabr. ssp. floccosa Cabr. trunk bark, guided by antiproliferative assays on 10 human cancer cell lines and the VERO cell line, yielded six known compounds identified as the triterpene bauerenyl acetate, the guaianolide 11α,13‐dihydrozaluzanin C and the dimeric guaianolides 10‐desoxygochnatiolide A, gochnatiolide A, 8‐hydroxi‐10‐desoxygochnatiolide A and 8‐hydroxigochnatiolide A. Extracts, fractions of extracts and isolated compounds were tested in vitro against a panel of human cancer cell lines, including U251 (glioma, CNS), UACC‐62 (melanoma), MCF‐7 (breast), NCI‐ADR/RES (drug‐resistant ovarian), 786.0 (kidney), NCI‐H460 (lung, no small cells), PC‐3 (prostate), OVCAR‐3 (ovarian), HT‐29 (colon), K562 (leukemia) and against the VERO no cancer cell line. Bauerenyl acetate was inactive, while 11α,13‐dihydrozaluzanin C showed weak activity against UACC62 and the VERO cell line. The most active compounds were 10‐desoxygochnatiolide A and gochnatiolide A, which inhibited the growth of kidney, melanoma, ovarian‐resistant and glioma cell lines with values of TGI (total growth inhibition) varying 0.21–1.09 µg/mL. This is the first report about cytotoxic activity of dimeric lactones against cell lines. Copyright © 2011 John Wiley & Sons, Ltd.     

Long‐chain Alkanes and ent‐Labdane‐type Diterpenes from Gymnosperma glutinosum with Cytotoxic Activity Against the Murine Lymphoma L5178Y‐R

The antitumor potential of Gymnosperma glutinosum was previously reported using the in vitro and in vivo L5178Y‐R lymphoma murine model. The present study was carried out to isolate and identify the cytotoxic compounds present in the Gymnosperma glutinosum leaf hexane extract. Gymnosperma glutinosum was collected in the semi‐arid region of Escobedo, State of Nuevo León, México, but it is commonly found in northeastern Mexico; it is traditionally used as a treatment for diarrhea, ulcers and rheumatism. G. glutinosum leaves were extracted with hexane and further fractioned and subfractioned over silica gel by gradient elution with hexane, chloroform, ethyl acetate and methanol. The cytotoxicity of fractions and subfractions was assessed in vitro against L5178Y‐R lymphoma cells. Structure elucidation of the active compounds was determined by spectroscopic methods. Fractions and subfractions showed significant (p < 0.05) and concentration‐dependent 20% to 56% cytotoxicity against L5178Y‐R cells at concentrations ranging from 7.8 µg/mL to 500 µg/mL. The bioassay‐guided fractionation of the hexane extract resulted in the isolation and identification of the alkane hentriacontane and the diterpene ent‐labd‐7‐en‐13S,14R,15‐triol as the metabolites responsible for the activity. Copyright © 2012 John Wiley & Sons, Ltd.     

Preparation of novel apigenin‐enriched,liposomal and non‐liposomal,antiinflammatory topical formulations as substitutes for corticosteroid therapy

Two oil‐in‐water formulations, containing equal amounts of apigenin‐enriched chamomile flower extracts, for potential use as topical antiinflammatory agents, were prepared and their physicochemical properties evaluated. A pilot clinical study was then carried out to assess patient acceptability and efficacy. The creams were either non‐liposomal or liposomal. The liposomal formulations were more viscous, thus producing superior release characteristics in vitro. The clinical study also showed that the liposomal creams were, as antiinflammatory agents, slightly more effective in vivo than the non‐liposomal formulations. These results suggest that there is scope for the further development of even more effective and safer alternatives to corticosteroids. Copyright © 2010 John Wiley & Sons, Ltd.     

Investigations into the Folkloric Antimicrobial Activities of Landolphia owrrience

The folkloric antimicrobial activities of Landolphia owrrience were investigated using ether, ethylacetate and n -butanol extracts of the leaves as well as six TLC components (A–F) of the n -butanol extract. The activities of these extracts and TLC components were investigated against Escherichia coli, Bacillus subtilis, Candida albicans and Aspergillus niger using the agar diffusion method. The n -butanol fraction as well as its TLC fractions showed marked antimicrobial activities against the four organisms. The n -butanol extract was active against all the organisms except B. subtilis . The TLC fractions A, D and E showed similar antimicrobial spectra and were active against E. coli, B. subtilis and C. albicans. Fractions B and F possessed similar antimicrobial spectra, showing activity against B. subtilis and C. albicans . Fractions B and F have the greatest fungicidal activity while fraction A has the greatest antibacterial activity based on the MIC results. These activities have been attributed to the presence of steroids, saponins, tannins and saponins probably as glycosides. © 1997 by John Wiley & Sons, Ltd.     

Genotoxic and clastogenic activity of saponins extracted from Nauclea bark as assessed by the micronucleus and the comet assays in Chinese Hamster Ovary cells

Ethnopharmacological relevance

Bark extracts of Nauclea latifolia, Nauclea diderrichii, Nauclea pobeguinii and Nauclea vandergutchii are used in traditional medicine in West and South Africa for the treatment of fevers, diarrhea and malaria.

Aim of the study

To estimate the possible long-term toxicity and genotoxicity of plant extracts (dichloromethane, methanol, water/methanol, water) and saponins.

Materials and methods

The clastogenicity of plant extracts and saponins was assessed by the micronucleus assay performed on Chinese Hamster Ovary cells. The DNA-damaging activity of saponin mixture was assessed by the comet assay on Chinese Hamster ovary cells.

Results

Hydromethanolic extracts from Nauclea latifolia, Nauclea diderrichii and Nauclea pobeguinii exhibited a significant clastogenic/aneugenic activity without S9 mix. The hydromethanolic extract from Nauclea diderrichii was the most clastogenic/aneugenic fraction with a Minimal Active Concentration (MAC) of 23.1 μg mL⁻¹. It was submitted to a separation step leading to six main saponins identified as quinovic acid glycosides (saponins A, D, E, G, J, K). None of the isolated saponins exerted a significant clastogenic/aneugenic activity by the micronucleus assay, however a mixture made with equal quantities of each of the six saponins exhibited a direct genotoxic/clastogenic activity as assessed by both the micronucleus assay and the comet assay on Chinese Hamster Ovary cells.

Conclusion

Saponins present in the hydromethanolic extracts of Nauclea induced synergistic in vitro DNA-damage and chromosome mutations in mammalian cells. This genotoxic activity was probably due to the capacity of Nauclea saponins to reduce cell defense against oxidative stress through the inhibition of glutathione-S-transferase activity.     

In vitro anti‐adhesive activity of green tea extract against pathogen adhesion

Camellia sinensis polysaccharide has been reported to possess anti‐adhesive activity against pathogens. The present study was designed to investigate whether hot water extracts obtained from green tea leaves might inhibit pathogen adhesion to human or mouse cell lines. Green tea extract‐4 (CSI‐4) with the maximum yield of 4% (w/v) is composed of a major proportion of carbohydrates containing 40% uronic acids, but lack of catechins. It showed strong inhibitory activities against hemagglutination mediated by pathogens Helicobacter pylori, Propionibacterium acnes and Staphylococcus aureus with the minimum inhibitory concentrations of 0.01‐0.5 mg/mL. CSI‐4 further demonstrated an inhibitory effect on the adhesion of these pathogens to host cell lines with the IC₅₀ values (50% inhibition of adhesion) of 0.14–2.3 mg/mL. It exhibited the highest activity against P. acnes, but no inhibitory effects were observed against Lactobacillus acidophilus, Bifidobacterium bifidum, Escherichia coli, or Staphylococcus epidermidis. Our results suggest that CSI‐4 may exert a selective anti‐adhesive effect against certain pathogenic bacteria with no adverse effects against beneficial or commensal bacteria. Copyright © 2008 John Wiley & Sons, Ltd.