Susanne Valcic

Inhibitory effect of six green tea catechins and caffeine on the growth of four selected human tumor cell lines.

Green tea is an aqueous infusion of dried unfermented leaves of Camellia sinensis (family Theaceae) from which numerous biological activities have been reported including antimutagenic, antibacterial, hypocholesterolemic, antioxidant, antitumor and cancer preventive activities. From the aqueous-alcoholic extract of green tea leaves, six compounds (+)-gallocatechin (GC), (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), (−)-epigallocatechin gallate (EGCG) and caffeine, were isolated and purified. Together with (+)-catechin, these compounds were tested against each of four human tumor cell lines (MCF-7 breast carcinoma, HT-29 colon carcinoma, A-427 lung carcinoma and UACC-375 melanoma). The three most potent green tea components against all four tumor cell lines were EGCG, GC and EGC. EGCG was the most potent of the seven green tea components against three out of the four cell lines (i.e. MCF-7 breast cancer, HT-29 colon cancer and UACC-375 melanoma). On the basis of these extensive in vitro studies, it would be of considerable interest to evaluate all three of these components in comparative preclinical in vivo animal tumor model systems before final decisions are made concerning which of these potential chemopreventive drugs should be taken into broad clinical trials.

Inhibition of ultraviolet B-induced c-fos gene expression and p38 mitogen-activated protein kinase activation by (-)-epigallocatechin gallate in a human keratinocyte cell line

(‐)‐Epigallocatechin gallate (EGCG), the major polyphenol isolated from green tea, is an active chemoprevention agent against cancer. However, the molecular mechanisms that underlie the inhibitory effects of EGCG are not well understood. In this study, we tested the effects of EGCG on ultraviolet (UV) B radiation–induced c‐fos gene expression in a human keratinocyte cell line, HaCaT. EGCG inhibited UVB‐induced steady‐state message and transcriptional activation of the c‐fos gene in a dose‐dependent manner. Western analyses further indicated that EGCG had an inhibitory effect on UVB‐induced accumulation of the c‐fos protein within the same dose range. To further examine the mechanism by which EGCG inhibits UVB‐induced c‐fos expression, we tested the effect of EGCG on upstream activators of the c‐fos gene. We found that EGCG significantly inhibited activation of p38 mitogen‐activated protein kinase but not c‐jun NH2‐terminal kinase or extracellular signal‐regulated protein kinase activation. Our previous studies have indicated that UVB‐induced c‐fos expression may play a key role in UVB‐induced activation of the activator protein‐1 transcription factor and EGCG‐inhibited, UVB‐induced activation of AP‐1 in HaCaT cells. Because AP‐1 is important for tumor promotion and c‐fos is a major component of AP‐1, the inhibitory effects of EGCG on c‐fos expression may further explain the anti–tumor‐promoting effects of EGCG. Mol. Carcinog. 24:79–84, 1999.

Prevention of photocarcinogenesis by topical administration of pure epigallocatechin gallate isolated from green tea.

Topical application of purified (-)-epigallocatechin-3-gallate (EGCG), a polyphenolic antioxidant isolated from green tea, inhibited photocarcinogenesis in BALB/cAnNHsd mice with no visible toxicity. Mice were treated with 0, 10, or 50 mg of EGCG in 200 microliters of acetone three times weekly for three weeks before ultraviolet (UV) treatments began and throughout the experiment. UV radiation consisted of five 30-minute exposures per week to banks of six FS40 Westinghouse sunlamps for 25 weeks. In the photocarcinogenesis study, mice received a total dose of approximately 2.1 x 10(6) J/m2. Skin cancer incidence in UV-irradiated mice was 96% at 28 weeks after the first UV treatment; EGCG at 10 or 50 mg reduced this incidence to 62% and 29%, respectively. UV-induced immunosuppression, assessed by the inability of UVB-irradiated mice to reject a syngeneic antigenic tumor, was not influenced by topical EGCG. Oral administration of 0, 100, or 500 mg of pure EGCG per liter of drinking water (approximately 0, 0.56, or 2.8 mg/day, respectively) did not decrease UV-induced skin tumor incidence, rate of primary tumor growth, or inability to reject antigenic tumors. Thus induction of skin tumors by UV radiation was significantly reduced by topical, but not by oral, administration of purified EGCG through a mechanism distinct from inhibition of photoimmunosuppression.

Pharmacokinetics of the green tea derivative, EGCG, by the topical route of administration in mouse and human skin

Purpose: (−)-Epigallocatechin gallate (EGCG), the main physiologically active polyphenol of green tea, is associated with antitumor and antimutagenic activities. The goal of this study was to determine the stability and pharmacokinetic parameters of pure EGCG administered topically to human and mouse skin. Methods: EGCG was investigated by measuring drug levels of a 10% ointment formulation stored under different conditions over a period of 6 months. To determine pharmacokinetic parameters of EGCG following topical application, EGCG was applied as 10% EGCG in hydrophilic ointment USP to full-thickness mouse or human skin in vitro. The transdermal and intradermal. Penetration of EGCG was measured by reverse phase HPLC assays at different time-points. Results: The stability of EGCG in hydrophilic ointment USP was dependent on time, temperature and the degree of oxidation. For example, 10% EGCG was lost after 2 days at 37 °C, but the same formulation supplemented with 0.1% butylated hydroxytoluene (BHT) had significantly longer stability with ≥90% EGCG remaining after 130 days at 37 °C. Topical application of EGCG in hydrophilic ointment USP to human or mouse skin resulted in substantial intradermal uptake of up to 1–20% of the applied dose. However, transdermal penetration was observed only in mouse skin. Conclusion: The present study showed that topical application of EGCG in hydrophilic ointment USP achieved high concentrations in skin but negligible systemic availability. The drug was susceptible to oxidation, but if supplemented with BHT, the hydrophilic ointment formulation could potentially be used in clinical trials of skin cancer prevention.

Potentiometric and 1H NMR studies of complexation of Al3+ with (−)-epigallocatechin gallate, a major active constituent of green tea

The acid dissociation of (-)-epigallocatechin gallate (abbreviated as egcg) and its complexation with Al(3+) were studied by potentiometric titrations, and were compared with those of (-)-epicatechin (ec) and (-)-epigallocatechin (egc). In Al(3+)-ec and Al(3+)-egc reaction systems, [Al(LH(-2))](+), [Al(LH(-2))(OH)](0), and [Al(LH(-2))(2)](-) are formed, as reported for Al(3+)-catechin (c). Reactions between Al(3+) and egcg at pH <4.1 yield AlLH(-2) and AlLH(-3) species. The 1H NMR studies have shown that two hydroxyl groups of the gallate (D) ring are deprotonated and coordinated to an Al(3+) ion in [Al(egcgH(-2))](+). The AlLH(-3) species of egcg is supposed to be formulated as [Al(egcgH(-3))](0) in which one hydroxyl group of the pyrogallol (B) ring and two hydroxyl groups of the D ring are deprotonated; an Al(3+) ion is coordinated to two oxygen atoms of the D ring and one oxygen atom from the B ring of the neighboring chelate molecule, resulting in the formation of a polymeric structure. In the Al(3+) complex of egcg, the gallate group forms major coordinate bonds and results in solution properties that are different from those of ec, egc and c which have no gallate group.

Antitubercular activity of pentacyclic triterpenoids from plants of Argentina and Chile.

Screening of plants from South America for antitubercular activity and subsequent assay-guided fractionation resulted in the isolation and characterization of several pentacyclic triterpenoids. The MIC values of 22 triterpenoids were determined using the radiorespiratory BACTEC assay and range from 8 microM to above 128 microM. The structure-activity relationships are discussed.

Phytochemical, morphological, and biological investigations of propolis from Central Chile.

Abstract Propolis from Central Chile was investigated for its plant origin by microscopical analysis of pollen grains and leaf fragments found in the sample. The pollen grains that appear with significant higher frequency in the sample corresponded to four native and two introduced species, whereas leaf fragments corresponded to four native species. Seventeen phenolic com pounds that belong to the phenylpropane, benzaldehyde, dihydrobenzofuran, or benzopyran classes, were isolated from an organic extract that was found to have a moderate growth inhibitory activity against Mycobacterium avium , M. tuberculosis, and two strains of Staphylococcus aureus. The components responsible for activity were determined.

13-Epi-homoverrucosane derivatives and other diterpenes from Plagiochila (hepaticae)☆

Abstract Four new 13-epi-homoverrucosane-type diterpenes: 13-epi-homoverrucosan-5β,6β-diol 2 ; 13-epi-homoverrucosan-5β,6β-diol-8-one 3 ; 13-epi-homoverrucosan-6β-ol-5-one 4 ; 13-epi-homoverrucosan-5β,6β,8β-triol 5 , along with the known 13-epi-homoverrucosan-5β-ol 1 and two known fusicoccane-type diterpenes, fusicogigantone A 6 and B 7 , were isolated from Plagiochila cristata collected from the wild. Only the two fusicoccane-type diterpenes were isolated from Plagiochila adianthoides grown in axenic culture. All structures were elucidated by spectral data.

Antioxidant reactions of green tea catechins and soy isoflavones

Green tea, a popular beverage brewed from dried leaves of the tea bush (Camellia sinensis) is distinguished by the presence of a group of polyphenols called flavanols or catechins (Graham, 1992). In recent years, the principal green tea catechins, i.e. (-)-epicatechin, (-)-epicatechin-3-gallate, (-)-epigallocatechin (EGC), and (-)-epigallocatechin-3-gallate (EGCG) have been recognized to be effective protectants against certain forms of cancer (Katiyar et al., 1992; Yang et al., 1993). These protective effects often have been attributed to antioxidant actions (Jovanovic et al., 1994; Terao et al., 1994; Salah et al., 1995; Kondo et al., 1999). The potential role of soy products in cancer prevention also has received much attention in recent years. Epidemiological data indicate that consumption of soybean-containing diets is associated with a lower incidence of certain human cancers in Asian compared to Caucasian populations (King et al., 1980; Locke et al., 1980). Genistein is one of the two principal isoflavones found in soy (Murphy, 1982) and, like catechins, is thought to act in large part through its ability to scavenge oxidants involved in carcinogenesis (Wei et al., 1993).

Pentacyclic triterpenes from Chuquiraga ulicina

Four taraxastane triterpenes, 3 beta-acetoxy-6 beta-hydroxytaraxasta-20-ene, 6 beta-hydroxytaraxasta-20-en-3-one, 6 beta-hydroxytaraxasta-20-ene 3 beta-palmitate and 3 beta,6 beta-dihydroxytaraxasta-20-ene were isolated from the dichloromethane-methanol extract of Chuquiraga ulicina ssp. ulicina together with the known triterpenes lupeol, lupenyl acetate, lupenone, friedelinol, 3 beta-acetoxy-30-nor-lupan-20-one, and 30-nor-lupan-3 beta-ol-20-one.