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Two new sulfated sesterterpene alkaloids, 19-oxofasciospongine A (3) and fasciospongine C (4), and a new sesterterpene sulfate, 25-hydroxyhalisulfate 9 (5), along with two known sesterterpene sulfates, halisulfates 7 (6) and 9 (7), were isolated from an organic extract of the marine sponge Fasciospongia sp. The structures of the new compounds were established on the basis of one- and two-dimensional NMR spectroscopic studies as well as by HRESIMS analysis. Compounds 1-7 exhibited inhibitory activity against Streptomyces 85E in the hyphae-formation inhibition assay. Compounds 1, 2, and 4-7 were not cytotoxic when tested at 20 microg/mL with MCF-7, LNCaP, and LU cell lines. Only compound 3 demonstrated a moderate cytotoxic effect on the MCF-7 (IC(50) 13.4 microM), LNCaP (IC(50) 21.8 microM), and LU-1 cells (IC(50) 5.0 microM), respectively.

Fractionation of an ethyl acetate-soluble extract of the stem bark of Dichapetalum gelonioides, collected in the Philippines, using the LNCaP (hormone-dependent human prostate) cell line as a monitor, led to the purification of three dichapetalin-type triterpenoids [dichapetalins A (1), I (2), and J (3)], along with two dolabrane norditerpenoids (6, 7), and the additional triterpenoids zeylanol (8), 28-hydroxyzeylanol (9), and betulinic acid. Since compounds 1-3 exhibited promising selectivity against the SW626 (human ovarian cancer) cell line, a re-collection of the plant material was carried out, to obtain more of these compounds for additional biological testing. Two further phenylpyranotriterpenoids [dichapetalins K (4) and L (5)] were isolated from the re-collected plant material. The structures of the new compounds 2-5 and 9 were determined on the basis of spectroscopic data interpretation, and the relative configuration of 6 was confirmed using X-ray crystallography. Compounds 4-6 and the methyl ester, 6a, exhibited broad cytotoxic activity when tested against a panel of human tumor cell lines. Dichapetalin A (1) was not active when evaluated in an in vivo hollow fiber assay in the dose range 1-6 mg/kg.

Two new compounds, pulveraven A (1) and pulveraven B (2), as well as vulpinic acid (3) and its previously unreported polymorph were isolated from the fruiting body of Pulveroboletus ravenelii. The structures were determined using a combination of NMR, MS, IR, optical rotation, molecular modeling, and X-ray analysis. The isolates were evaluated for antimicrobial activity as well as their potential to inhibit cyclooxygenase (COX) activity and carcinogen-induced preneoplastic lesion formation with mouse mammary organ culture (MMOC).

Nine tropane alkaloid aromatic esters (1−9) were isolated from the roots of Erythroxylum pervillei by following their potential to reverse multidrug-resistance with vinblastine-resistant oral epidermoid carcinoma (KB-V1) cells. All isolates, including seven new structures (3−9), were evaluated against a panel of human cancer cell lines, and it was found that alkaloids 3 and 5−9 showed the greatest activity with KB-V1 cells assessed in the presence of vinblastine, suggesting that these new compounds are potent modulators of P-glycoprotein. Confirmatory results were obtained with human ovarian adenocarcinoma (SKVLB) cells evaluated in the presence of adriamycin and synergistic studies performed with several cell lines from the NCI tumor panel. The structures of the new compounds were determined using spectroscopic techniques. Single-crystal X-ray analysis was performed on the monoester, tropane-3α,6β,7β-triol 3-phenylacetate (1).

A known aporphine alkaloid, (-)-roemerine [1], isolated from the leaves of Annona senegalensis, was found to enhance the cytotoxic response mediated by vinblastine with multidrug-resistant KB-V1 cells. In the absence of vinblastine, no significant cytotoxicity was observed with KB-3 or KB-V1 cells (ED50 > 20 micrograms/ml), and several other human tumor cell lines were also relatively insensitive. As indicated by its ability to inhibit ATP-dependent [3H]vinblastine binding to multidrug-resistant KB-V1 cell membrane vesicles, (-)-roemerine appears to function by interacting with P-glycoprotein. In addition to alkaloid 1, three inactive compounds [the aporphine alkaloid(-)-isocorydine (reported in the levo-configuration for the first time), and the lignans (+/-)-8,8'-bisdihydrosiringenin [2] (a new natural product), and (+)-syringaresinol] were also isolated.

From the medicinal plant Isodon rubescens, we isolated two novel diterpenes, rubesanolides A (1) and B (2). The compounds contain a unique β-lactone subgroup. This is the first discovery for a natural diterpene having rings A, B, and C in chair, boat, and twist-chair conformations, respectively. The structures were elucidated by analysis of spectroscopic data, and the absolute configuration of 1 was determined by X-ray diffraction.

Three new dammarane triterpenes, bruguierins A-C (1-3), were isolated from a petroleum ether extract of the flowers of Bruguiera gymnorrhiza. Their structures were determined on the basis of physical and spectroscopic data interpretation. With stably transfected HepG2 cells, the three isolates activated antioxidant response element (ARE luciferase activation) with EC(50) values of 7.8, 9.4, and 15.7 microM, respectively. Bruguierin A (1) also inhibited phorbol ester-induced NFkappaB (nuclear factor-kappaB) luciferase activation with an IC(50) value of 1.4 microM and selectively inhibited cyclooxygenase-2 (COX-2) activity with an IC(50) value of 0.37 microM. Compounds 2 and 3 were not active in these bioassays.

A new prenylated flavonol, petalopurpurenol (1), and a known dihydroflavonol, petalostemumol (2), have been isolated by DNA scission-guided fractionation of the organic portion of a 20% MeOH/CHCl 3 /H 2 O partition of a 50% MeOH/CHCl 3 extract of the roots of Petalostemon purpureus. Compound 2 displayed moderate activity in DNA-scission assay. Both compounds 1 and 2 were evaluated for cytotoxicity in a panel of human cancer cell lines. The structures of petalopurpurenol (1) and petalostemumol (2) were determined by spectroscopic analysis.

Moderate consumption of wine is associated with a reduced risk of cancer. Grape plant cell cultures were used to purify 12 phenols: the stilbenoids trans-astringin, trans-piceid (2), trans-resveratroloside, trans-resveratrol, trans-piceatannol, cis-resveratroloside, cis-piceid, and cis-resveratrol; the flavans (+)-catechin, (-)-epicatechin, and epicatechin 3-O-gallate; and the flavan dimer procyanidin B2 3'-O-gallate. These compounds were evaluated for potential to inhibit cyclooxygenases and preneoplastic lesion formation in carcinogen-treated mouse mammary glands in organ culture. At 10 micrograms/ml, trans-astringin and trans-piceatannol inhibited development of 7,12-dimethylbenz[a]anthracene-induced preneoplastic lesions in mouse mammary glands with 68.8% and 76.9% inhibition, respectively, compared with untreated glands. The latter compound was the most potent of the 12 compounds tested in this assay, with the exception of trans-resveratrol (87.5% inhibition). In the cyclooxygenase (COX)-1 assay, trans isomers of the stilbenoids appear to be more active than cis isomers: trans-resveratrol [50% inhibitory concentration (IC50) = 14.9 microM, 96%] vs. cis-resveratrol (IC50 = 55.4 microM). In the COX-2 assay, among the compounds tested, only trans- and cis-resveratrol exhibited significant inhibitory activity (IC50 = 32.2 and 50.2 microM, respectively). This is the first report showing the potential cancer-chemopreventive activity of trans-astringin, a plant stilbenoid recently found in wine. trans-Astringin and its aglycone trans-piceatannol were active in the mouse mammary gland organ culture assay but did not exhibit activity in COX-1 and COX-2 assays. trans-Resveratrol was active in all three of the bioassays used in this investigation. These findings suggest that trans-astringin and trans-piceatannol may function as potential cancer-chemopreventive agents by a mechanism different from that of trans-resveratrol.

The roots of Lavandula stoechas ssp. stoechas afforded eleven known triterpenes, two steroids and two aromatics, in addition to two new triterpenes, 18-hydroxy-27-norolean-12,14-dien-30-al-28-oic acid and 3 beta-hydroxy-1-oxo-olean-12-ene-30-al-28-oic acid. Their structures were determined by spectroscopic analyses. The chloroform extract and some isolated compounds were evaluated for their growth inhibitory activity against several mammalian cell lines.

Nine tropane alkaloid aromatic esters (1-9) were isolated from the roots of Erythroxylum pervillei by following their potential to reverse multidrug-resistance with vinblastine-resistant oral epidermoid carcinoma (KB-V1) cells. All isolates, including seven new structures (3-9), were evaluated against a panel of human cancer cell lines, and it was found that alkaloids 3 and 5-9 showed the greatest activity with KB-V1 cells assessed in the presence of vinblastine, suggesting that these new compounds are potent modulators of P-glycoprotein. Confirmatory results were obtained with human ovarian adenocarcinoma (SKVLB) cells evaluated in the presence of adriamycin and synergistic studies performed with several cell lines from the NCI tumor panel. The structures of the new compounds were determined using spectroscopic techniques. Single-crystal X-ray analysis was performed on the monoester, tropane-3 alpha,6 beta,7 beta-triol 3-phenylacetate (1).

From the bulbs and leaves of Hymenocallis expansa (Amaryllidaceae), three alkaloid constituents were identified: (+)-tazettine, (+)-hippeastrine, and (-)-haemanthidine. These alkaloids demonstrated significant cytotoxicity when tested against a panel of human and murine tumor cell lines.

Trans-3,4',5-trihydroxystilbene (resveratrol), a phytoalexin present in grapes and grape products such as wine, has been identified as a chemopreventive agent. Recent studies performed with MCF-7 human breast cancer cells have demonstrated superestrogenic effects with resveratrol. In contrast, studies performed using estrogen receptor-transfected cell lines have shown that resveratrol acts as a mixed agonist/antagonist. The major objective of this study was to characterize the estrogen-modulatory effects of resveratrol in a variety of in vitro and in vivo mammary models. Thus, the effect of resveratrol alone and in combination with 17beta-estradiol (E2) was assessed with MCF-7, T47D, LY2, and S30 mammary cancer cell lines. With cells transfected with reporter gene systems, the activation of estrogen response element-luciferase was studied, and using Western blot analysis, the expression of E2-responsive progesterone receptor (PR) and presnelin 2 protein was monitored. Furthermore, the effect of resveratrol on formation of preneoplastic lesions (induced by 7,12-dimethylbenz(a)anthracene) and PR expression (with or without E2) was evaluated with mammary glands of BALB/c mice placed in organ culture. Finally, the effect of p.o. administered resveratrol on N-methyl-N-nitrosourea-induced mammary tumors was studied in female Sprague Dawley rats. As a result, in transient transfection studies with MCF-7 cells, resveratrol showed a weak estrogenic response, but when resveratrol was combined with E2 (1 nM), a clear dose-dependent antagonism was observed. Similar mixed estrogenic/antiestrogenic effects were noted with S30 cells, whereas resveratrol functioned as a pure estrogen antagonist with T47D and LY2 cells. Furthermore, in MCF-7 cells, resveratrol induced PR protein expression, but when resveratrol was combined with E2, expression of PR was suppressed. With T47D cells, resveratrol significantly down-regulated steady-state and E2-induced protein levels of PR. With LY2 and S30 cells, resveratrol down-regulated presnelin 2 protein expression. Using the mouse mammary organ culture model, resveratrol induced PR when administered alone, but expression was suppressed in the presence of E2 (1 nM). Furthermore, resveratrol inhibited the formation of estrogen-dependent preneoplastic ductal lesions induced by 7,12-dimethylbenz(a)anthracene in these mammary glands (IC50 = 3.2 microM) and reduced N-methyl-N-nitrosourea-induced mammary tumorigenesis when administered to female Sprague Dawley rats by gavage. Therefore, in the absence of E2, resveratrol exerts mixed estrogen agonist/antagonist activities in some mammary cancer cell lines, but in the presence of E2, resveratrol functions as an antiestrogen. In rodent models, carcinogen-induced preneoplastic lesions and mammary tumors are inhibited. These data suggest that resveratrol may have beneficial effects if used as a chemopreventive agent for breast cancer.

Trans-3,4',5-trihydroxystilbene (resveratrol), a polyphenolic compound found in the human diet, was reported recently to serve as an estrogen agonist with cultured MCF-7 cells transfected with estrogen response element-luciferase reporter plasmids. As currently shown, treatment of cultured human endometrial adenocarcinoma (Ishikawa) cells with resveratrol (concentrations as high as 10 microM) did not significantly increase the levels of an estrogen-inducible marker enzyme, alkaline phosphatase. To the contrary, when alkaline phosphatase was induced by treatment with 1 nM of 17beta-estradiol (E(2)), resveratrol exhibited a dose-dependent decrease in activity (IC(50) = 2.3 microM). Furthermore, when Ishikawa cells were treated with resveratrol as a single agent, estrogen-inducible progesterone receptor (PR) was not enhanced, and PR expression induced by treatment with E(2) was inhibited by resveratrol in a dose-dependent fashion at both the mRNA and protein levels. In addition, resveratrol mediated suppression of a functional activity of PR as demonstrated by down-regulation of alpha(1)-integrin expression induced by E(2) plus progesterone. With transient transfection experiments conducted with Ishikawa cells, antiestrogenic effects were confirmed by dose-dependent inhibition of E(2)-induced estrogen response element-luciferase transcriptional activity. Because resveratrol antagonized estrogenic effects in Ishikawa cells, competitive binding analyses were performed to examine the potential of displacing [(3)H]E(2) from human estrogen receptor (ER). Resveratrol showed no discernable activity with ER-alpha, but with ER-beta, E(2) was displaced with an IC(50) of 125 microM. However, mRNA and protein expression of ER-alpha but not ER-beta were suppressed by resveratrol in Ishikawa cells, in the concentration range of 5-15 microM. In addition, in the presence or absence of E(2), resveratrol inhibited Ishikawa cell proliferation in a time-dependent manner with cells accumulating in the S phase of the cycleor =48 h. This effect was reversible. Analysis of some critical cell cycle proteins revealed a specific increase in expression of cyclins A and E but a decrease in cyclin-dependent kinase 2. These data suggest resveratrol exerts an antiproliferative effect in Ishikawa cells, and the effect may be mediated by both estrogen-dependent and -independent mechanisms.

Non-physiological inducers of terminal differentiation have been used as novel therapies for the prevention and therapy of cancer. We have used cultured HL-60 promyelocytic cells to monitor differentiation, proliferation and cell death events as induced by a large set of extracts derived from plants. Screening of more than 1400 extracts led to the discovery of 34 with potent activity (ED508 mg/ml). Bioassay-guided fractionation led to the isolation of zapotin and 2',5,6-trimethoxyflavone as active principles from Casimiroa edulis, dibenzyltrisulfide and 2-[(phenylmethyl)dithio]ethanol as active principles from Petiveria alliacea, and desmethylrocaglamide from Aglaia ponapensis. Zapotin demonstrated the most favorable biological profile in that induction of differentiation correlated with proliferation arrest, and a lack of cytotoxicity. We conclude that the HL-60 cell model is a useful system for the discovery of novel pharmacophores with potential to suppress the process of carcinogenesis, and that flavonoids may be especially useful in this capacity.

P-Glycoprotein-mediated drug efflux can yield a multidrug-resistance (MDR) phenotype that is associated with a poor response to cancer chemotherapy. Pervilleine A, a novel tropane alkaloid obtained from a chloroform extract of Erythroxylum pervillei as the result of bioactivity-guided fractionation, was found to restore the vinblastine sensitivity of cultured multidrug-resistant KB-V1 and CEM/VLB(100) cells, with IC(50) values of 0.36 and 0.02 microM, respectively. Similarly, the chemosensitivity of KB-8-5 cells to colchicine was restored with an IC(50) value of 0.61 microM. The mechanism of this response was evaluated with a number of model systems. First, incubation of multidrug-resistant KB-V1 and CEM/VLB(100) cells with up to 45 microM pervilleine A for 72 h did not significantly affect either the transcription of MDR1, as revealed by reverse transcriptional-PCR-based analysis of MDR1 mRNA, or levels of P-glycoprotein, as shown by Western blots. ATP-dependent binding of [(3)H]vinblastine observed with isolated multidrug-resistant KB-V1 cell membrane vesicles was inhibited by pervilleine A in a dose-dependent manner, and kinetic analysis indicted competitive inhibition with respect to vinblastine binding with a K(i) of 7.3 microM. Consistent with this effect, intracellular accumulation of [(3)H]vinblastine was increased from 0.18 pmol [(3)H]vinblastine/50 x 10(4) cells to approximately 5 pmol [(3)H]vinblastine/50 x 10(4) cells in the presence of 40 microM pervilleine A. To explore the potential relevance of these responses, KB-V1 or KB-8-5 cells were placed in hollow fibers and implanted into NCr nu/nu mice. Cell growth was not significantly inhibited when vinblastine or pervilleine A were administered as single agents, but when used in combination, inhibition of up to 75% was observed. Equimolar doses of verapamil were less effective. These data suggest that pervilleine A is an effective inhibitor of P-glycoprotein and should be further evaluated for clinical utility.

Five known cardenolides, digitoxigenin (1), oleandrigenin (2), digitoxigenin alpha-L-cymaroside (3), digitoxigenin beta-gentiobiosyl-alpha-L-cymaroside (4), and delta 16-digitoxigenin beta-D-glucosyl-alpha-L-cymaroside (5), were isolated from the stems of Beaumontia brevituba Oliver by cytotoxicity-directed fractionation monitored by a cultured human lung cancer cell line. The cytotoxic activity of these compounds was evaluated with a panel of twelve human and murine cancer cell lines. The lignan glycoside, syringaresinol beta-D-glucoside, was obtained for the first time in the form of its levo-enantiomer.

Betulinic acid is a naturally occurring pentacyclic triterpenoid. Betulinic acid has recently been selected by the National Cancer Institute for addition into the RAID (Rapid Access to Intervention in Development) programme. The agent exhibits potential anti-tumour activity and functions in this regard via apoptosis. The objective of the present study was to determine the pharmacokinetics of betulinic acid in CD-1 mice. Serum samples were obtained at designed times after a single 250 or 500 mg/kg intraperitoneal (IP) dose of betulinic acid. Tissue samples (skin, heart, liver, spleen, kidney, lung, brain, colon, caecum, ovary, uterus, thymus, lymph node, bladder, perirenal fat, mammary gland and small intestine) were collected after betulinic acid administration (500 mg/kg). Betulinic acid was extracted with methylene chloride and quantitatively analysed by HPLC/MS. Oleanolic acid and madecassic acid were used as internal standards. Pharmacokinetic parameters were calculated using the WinNonlin pharmacokinetic software package. A two-compartment, first-order model was selected for pharmacokinetic modelling. The results showed that after IP 250 and 500 mg/kg betulinic acid, the serum concentrations reached peaks at 0.15 and 0.23 h, respectively. The 250 and 500 mg/kg above betulinic acid IP doses were found to have elimination half-lives of 11.5 and 11.8 h and total clearances of 13.6 and 13.5 L/kg/h, respectively. The pharmacokinetic parameters observed for IP betulinic acid 500 mg/kg in the skin of mice were as follows: k(a) (h(-1)) 0.257, k(10) (h(-1)) 0.234, t(1/2(alpha)) (h) 2.63, t(1/2(beta)) (h) 20.2, V (L/kg) 0.61, AUC (microg/h/mL) 3504, T(max) (h) 3.90 and C(max) (microg/mL) 300.9. The distribution of betulinic acid in tissues at 24 h post-IP administration in a descending order was as follows: perirenal fat, ovary, spleen, mammary gland, uterus, bladder, lymph node, liver, small intestine, caecum, lung, thymus, colon, kidney, skin, heart and brain.

Studies involving infectious, wild type HIV-1 must be performed under strict BSL-3 practice. We have employed a defective (deltaTat/Rev)MC99 and cloned 1A2 line, ie, mutated HIV-1 and Tat/Rev transfected cells to verify anti-HIV-1 activity in a BSL-2 laboratory. A number of extracts from various parts of 11 species of plants were studied. Results were correlated with those of an anti-HIV-1 reverse transcriptase (RT) assay.

Two dimeric naphthoquinones, diospyrin and isodiospyrin, isolated from the root of Diospyros piscatoria (Gurke), a common ingredient in several folk medicines, have been shown to have a broad spectrum of antibacterial activity. The minimum inhibitory concentrations (MICs) of diospyrin against Streptococcus pyogenes ATCC 12344 and Streptococcus pneumoniae ATCC 33400 ranged from 1.56 to 50 microg/mL. While those against Salmonella choleraesuis serotype typhi (S. typhi), ATCC 6539 and Mycobacterium chelonae ATCC 19977 were between 25 and 100 microg/mL. Isodiospyrin was more active than its racemic isomer diospyrin. The MICs against Gram-positive bacteria ranged from 0.78 to 50 microg/mL. While those against Pseudomonas aeruginosa ATCC 15443 and S. typhi ranged from 50 to 100 microg/mL. The MIC for M. chelonae was between 6.25 and 25 microg/mL. MICs were found to increase with the concentration of cells used for the inoculum. The MICs for Bacillus subtilis ATCC 6633 increased up to the highest concentration of cells tested. The same phenomenon was observed on M. chelonae, but with better effect in the latter. The kinetics of bacteria studies against both B. subtilis and M. chelonae increases with increasing concentration of isodiospyrin tested. Two tetrameric forms of plumbagin were isolated. The naphthoquinone bisisodiospyrin, gave MIC values between 300 and 400 micro g/mL. The second, as yet unidentified tetramer, was not active at 500 micro g/mL.

Since reactive oxygen radicals play an important role in carcinogenesis and other human disease states, antioxidants present in consumable fruits, vegetables, and beverages have received considerable attention as cancer chemopreventive agents. Thus, in order to identify antioxidants in plant extracts, test materials were assessed for potential to scavenge stable 1,2-diphenyl-2-picrylhydrazyl (DPPH) free radicals, reduce TPA-induced free radical formation in cultured HL-60 human leukemia cells, and inhibit responses observed with a xanthine/xanthine oxidase assay system. Approximately 700 plant extracts were evaluated, and 28 were found to be active in the DPPH free radical scavenging assay. Based on secondary analyses performed to assess inhibition of 7,12-dimethylbenz(a)anthracene-induced preneoplastic lesion formation with a mouse mammary organ culture model, Chorizanthe diffusa Benth. (Polygonaceae), Mezoneuron cucullatum Roxb. (Leguminosae), Cerbera manghas L. (Apocynaceae) and Daphniphyllum calycinum Benth. (Daphniphyllaceae) were selected and subjected to bioassay-guided fractionation. 5,7,3',5'-Tetrahydroxy-8,4'-dimethoxyflavonol, 5,8,4'-trihydroxy-7,3'-dimethoxyflavonol, 5,3',4'-trihydroxy-7-methoxyflavonol, and 6,3',4'-trihydroxy-7-methoxyflavonol were identified as active principles from C. diffusa. Piceatannol, trans-resveratrol, apigenin and scirpusin A were found as the active principles of M. cucullatum, olivil, (-)-carinol, and (+)-cycloolivil were active principles from C. manghas, and 5,6,7,4'-tetrahydroxyflavone 3-O-rutinoside and kaempferol 3-O-neohesperidoside were active principles from D. calycinum. Of these substances, the hydroxystilbenes piceatannol and transresveratrol have thus far been shown to inhibit carcinogen-induced preneoplastic lesion formation in the mouse mammary gland organ culture model.

Resveratrol (3,5,4'-trihydroxy-trans-stilbene) is a naturally occurring compound shown to inhibit carcinogen-induced preneoplastic lesion formation in mouse mammary organ culture and tumorigenesis in the two-stage mouse skin model. Cancer chemopreventive potential was also suggested in various assays reflective of the three major stages of carcinogenesis. Anti-initiation activity was indicated by its antioxidant and antimutagenic effects, inhibition of the hydroperoxidase function of cyclooxygenase (COX), and induction of phase II drug-metabolizing enzymes. Antipromotion activity was indicated by antiinflammatory effects, inhibition of production of arachidonic acid metabolites catalyzed by either COX-1 or COX-2, and chemical carcinogen-induced neoplastic transformation of mouse embryo fibroblasts. Antiprogression activity was demonstrated by its ability to induce human promyelocytic leukemia (HL-60) cell differentiation. Moreover, pretreatment of mouse skin with resveratrol significantly counteracted 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced oxidative stress, as evidenced by numerous biochemical responses. Resveratrol reduced the generation of hydrogen peroxide, and normalized levels of myeloperoxidase and oxidized-glutathione reductase activities. It also restored glutathione levels and superoxide dismutase activity. As judged by the reverse transcriptase-polymerase chain reaction, resveratrol selectively inhibited TPA-induced expression of c-fos and transforming growth factor-beta 1 (TGF-beta 1), but did not affect other TPA-induced gene products including COX-1, COX-2, c-myc, c-jun, and tumor necrosis factor-alpha. These data indicate that resveratrol may interfere with reactive oxidant pathways and/or modulate the expression of c-fos and TGF-beta 1 to inhibit tumorigenesis in mouse skin. As reported herein, in addition to the activities described above, resveratrol inhibited the de novo formation of inducible nitric oxide synthase (iNOS) in mouse macrophages stimulated with lipopolysaccharide. This finding suggests an additional mechanism by which resveratrol may function as a cancer chemopreventive agent.

A structurally diverse group of chemopreventive agents was evaluated using in vitro biomarkers of the carcinogenesis process. With cultured human bronchial epithelial (BEAS-2B) cells, sulfur-containing compounds such as 1.2-dithiole-3-thione and sulforaphane, and phenolic compounds such as caffeic acid phenethyl ester and genistein, showed potent inhibition of benzo(a)pyrene [B(a)P] metabolite-DNA binding. Phenolic compounds also demonstrated strong antioxidant activity. Most of the test compounds did not inhibit 12-O-tetradecanoylphorbol 13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity with cultured mouse epidermal ME 308 cells, with the exception of sulfur-containing compounds, 1,2-dithiole-3-thione and sulforaphane, and a selenium compound, 1,4-phenylenebis (methylene)selenocyanate. With cultured Hepa 1c1c7 cells, sulforaphane and 1,2-dithiole-3-thione mediated strong induction of quinone reductase, and genistein and ursolic acid were moderate inducers. Chalcone, 1,4-phenylenebis (methylene)selenocyanate and caffeic acid phenethyl ester induced HL-60 cell differentiation. Interestingly, sulforaphane and caffeic acid phenethyl ester inhibited the total metabolism of benzo(a)pyrene with cultured BEAS-2B cells, and the distribution pattern of water-soluble metabolites was altered in comparison with the control groups. These data are suggestive of pleiotropic mechanisms that should prove beneficial when considering the chemopreventive activity of these substances. As a result, of the group of 25 agents tested, four were judged as superior cancer chemopreventive agents: caffeic acid phenethyl ester, 1,2-dithiole-3-thione, genistein, and sulforaphane.

Induction of phase II enzymes is an important mechanism of chemoprevention. In our search for novel cancer chemopreventive agents, 4'-bromoflavone (4'BF) was found to significantly induce quinone reductase (QR) activity in cultured murine hepatoma 1c1c7 cells (concentration to double activity: 10 nM) and effectively induce the alpha- and mu-isoforms of glutathione S-transferase in cultured H4IIE rat hepatoma cells with no observed toxicity. In short-term dietary studies, 4'BF was also shown to increase QR activity and glutathione levels in rat liver, mammary gland, colon, stomach, and lung in a dose-dependent manner. Induction mediated by 4'BF was bifunctional (induction of both phase I and phase II enzymes) and regulated at the transcriptional level, as revealed by transient transfection studies with plasmid constructs (pDTD-1097CAT, XRE-CAT, and ARE-CAT) and reverse transcription-PCR-based analysis of QR mRNA. In studies conducted with female Sprague Dawley rats, the effects of 4'BF on the relative induction levels of phase I and phase II enzyme activities were investigated in liver and mammary gland. Treatment with 4'BF and 7,12-dimethylbenz[a]anthracene (DMBA) or 4'BF alone did not significantly alter DMBA-induced cytochrome P4501A1 activity (phase I enzyme), but it significantly increased QR activity (phase II enzyme), compared with the DMBA treatment group. In addition, 4'BF was found to be a potent inhibitor of cytochrome P4501A1-mediated ethoxyresorufin-O-deethylase activity, with an IC50 of 0.86 microM. Furthermore, in studies conducted with cultured HepG2 or MCF-7 cells, 4'BF significantly reduced the covalent binding of metabolically activated benzo[a]pyrene to cellular DNA. On the basis of these results, a full-term cancer chemoprevention study was conducted with DMBA-treated female Sprague Dawley rats. Dietary administration of 4'BF (2000 and 4000 mg per kg of diet, from 1 week before to 1 week after DMBA) significantly inhibited the incidence and multiplicity of mammary tumors and greatly increased tumor latency. In summary, 4'BF can be viewed as a relatively simple, readily available, inexpensive compound that is a highly effective cancer chemopreventive agent. The full mechanism of action remains to be defined, but enhancement of detoxification pathways appears to be important.

Deguelin, a natural product isolated from Mundulea sericea (Leguminosae), was shown previously to mediate strong inhibition of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ornithine decarboxylase (ODC) activity in cell culture and to reduce the formation of preneoplastic lesions when mouse mammary glands were exposed to 7,12-dimethylbenz(a)anthracene. As reported currently, deguelin was synthesized and evaluated for chemopreventive activity in the two-stage 7,12-dimethylbenz(a)anthracene/TPA skin carcinogenesis model with CD-1 mice and in the N-methylnitrosourea mammary carcinogenesis model with Sprague Dawley rats. In the mouse skin study, deguelin reduced tumor incidence from 60% in the control group to 10% in the group treated with a dose of 33 microg, and multiplicity was reduced from 4.2 in the control group to 0.1 in the treatment group. When the dose was increased 10-fold to 330 microg, no tumors were observed in the treatment group. These results correlated with the potential of deguelin to inhibit TPA-induced mouse epidermal ODC activity. When applied topically as a single dose in a time range of 2 h before to 2 h after TPA treatment, deguelin (384 microg) reduced ODC induction by TPA (6.17 microg) by more than 85%. Time course studies indicated that deguelin (33 microg) inhibited TPA (1.17 microg)-induced ODC activity by 70% without affecting the kinetics of induction over a period of 10 h. Complete inhibition of ODC induction was observed at a dose of 330 microg of deguelin. In the rat mammary tumorigenesis study, intragastric administration of 2 or 4 mg of deguelin/kg of body weight daily, 5 days/week, reduced tumor multiplicity from 6.8 tumors/rat in the control group to 5.1 or 3.2 tumors/animal, respectively. At the 4 mg of deguelin/kg of body weight dose level, the tumor latency period was significantly increased. Tumor incidence, however, was unaffected. These data indicate that deguelin exhibits cancer chemopreventive effects in skin and mammary tumorigenesis models and that additional studies are warranted to characterize the cancer chemopreventive or chemotherapeutic potential of this substance more fully.

Deguelin, a plant-derived rotenoid, mediates potent chemopreventive responses through transcriptional regulation of phorbol ester-induced ornithine decarboxylase (ODC) activity. To explore the mechanism of this effect, the activity of this compound was evaluated with a number of model systems. Using cultured mouse epidermal 308 cells, the steady-state levels of both 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced ODC mRNA and c-fos were decreased by treatment with deguelin. ODC activity was also inhibited by bullatacin and various antimitotic agents (podophyllotoxin, vinblastine, and colchicine), but only deguelin and bullatacin were active as inhibitors of ODC levels in a TPA-independent c-Myc-mediated induction system using cultured BALB/c c-MycER cells. These results suggest that antimicrotubule effects, as mediated by rotenone, for example, are not responsible for inhibitory activity facilitated by deguelin. This was confirmed by use of an in vitro model of tubulin polymerization in which deguelin and a variety of other rotenoids were investigated and found to be inactive. As anticipated, however, NADH dehydrogenase was inhibited by these rotenoids. Moreover, inhibition of this enzyme correlated with a rapid depletion of ATP levels and potential to inhibit either TPA- or c-Myc-induced ODC activity. It therefore seems that deguelin-mediated interference with transient requirements for elevated energy can inhibit the induction of ODC activity and thereby yield a cancer chemopreventive response.

Chemoprevention involves the use of natural or synthetic substances to reduce the risk of developing cancer. Two dietary components capable of mediating chemopreventive activity in animal models by modulation of drug-metabolizing enzymes are sulforaphane, an aliphatic isothiocyanate, and brassinin, an indole-based dithiocarbamate, both found in cruciferous vegetables. We currently report the synthesis and activity of a novel cancer chemopreventive agent, (+/-)-4-methylsulfinyl-1-(S-methyldithiocarbamyl)-butane (trivial name, sulforamate), an aliphatic analogue of brassinin with structural similarities to sulforaphane. This compound was shown to be a monofunctional inducer of NAD(P)H:quinone oxidoreductase [quinone reductase (QR)], a Phase II enzyme, in murine Hepa 1c1c7 cell culture and two mutants thereof. Induction potential was comparable to that observed with sulforaphane (concentration required to double the specific activity of QR, approximately 0.2 microM), but cytotoxicity was reduced by about 3-fold (IC50 approximately 30 microm). In addition, sulforaphane, as well as the analogue, increased glutathione levels about 2-fold in cultured Hepa 1c1c7 cells. Induction of QR was regulated at the transcriptional level. Using Northern blotting techniques, time- and dose-dependent induction of QR mRNA levels were demonstrated in Hepa 1c1c7 cell culture. To further investigate the mechanism of induction, HepG2 human hepatoma cells were transiently transfected with QR-chloramphenicol acetyltransferase plasmid constructs containing various portions of the 5'-region of the QR gene. Sulforaphane and the analogue significantly induced (P0.0001) CAT activity at a concentration of 12.5 microM by interaction with the antioxidant responsive element (5-14-fold induction) without interacting with the xenobiotic responsive element. Moreover, both compounds significantly induced mouse mammary QR and glutathione S-transferase activity (feeding of 3 mg/mouse intragastric for 4 days), whereas the elevation of hepatic enzyme activities was less pronounced. Both sulforaphane and the analogue were identified as potent inhibitors of preneoplastic lesion formation in carcinogen-treated mouse mammary glands in organ culture (84 and 78% inhibition at 1 microm, respectively). On the basis of these results, the sulforaphane analogue can be regarded as a readily available promising new cancer chemopreventive agent.

A new polyacetylenic diepoxide compound, gummiferol [1] was isolated from the leaves of Adenia gummifera by KB cytotoxicity-guided fractionation. Compound 1 exhibited significant activity against the KB human cell line and a broad cytotoxic spectrum against other human cancer cell lines. The structure of 1 was established primarily on the basis of its spectral data.

Terminal differentiation of human promyelocytic leukemia (HL-60) cells can be induced by a variety of chemical agents and this process can be monitored readily by the generation of morphologically, histochemically, and functionally mature granulocytes and monocytes/macrophages. The availability of this model has heightened interest in the possible therapeutic role of inducers of myeloid differentiation for the treatment of leukemia and other neoplasms. In addition, however, potent cancer chemopreventive agents induce HL-60 cell differentiation at very low dose levels. Thus, as part of our search for natural product chemopreventive agents, extracts derived from nearly 400 plants were tested for their potential to induce HL-60 cell differentiation. As a result, 17 plant extracts were judged to be active (ED50 valuesor = 4 micrograms/ml). One of most potent leads was an extract derived from Dirca occidentalis Gray (Thymelaeaceae) (ED50, 0.14 micrograms/ml), and bioassay-guided fractionation led to the identification of genkwanin (I), (+/-)-lariciresinol (II) and sitoindoside II (IV) as active principles, with ED50 values of 18.3, 1.1 and 0.069 microM, respectively. Based on these data, we conclude that the HL-60 cell differentiation system is a valid and useful model for the discovery of natural product cancer chemopreventive or chemotherapeutic agents.

Four cytotoxic lignans were isolated from the stem bark of Bursera permollis (Burseraceae), namely, deoxypodophyllotoxin (1), beta-peltatin methyl ether (2), picro-beta-peltatin methyl ether (3), and dehydro-beta-peltatin methyl ether (4). Also isolated was the inactive lignan, nemerosin (5). Compounds 1 and 2 were potently cytotoxic when evaluated against a panel of human cancer cell lines.

Coronaridine [1], conoduramine [2], and voacamine [3], three indole alkaloids isolated from Peschiera laeta, have been found to enhance the cytotoxic response mediated by vinblastine [4] with multidrug-resistant KB cells. Inhibition of vinblastine binding with membrane vesicles isolated from this cell line was also assessed, and the bisindole alkaloids conoduramine [2] and voacamine [3] were found to be more potent inhibitory agents than the monomeric alkaloid, coronaridine [1]. Thus, these compounds appear to function by binding with P-glycoprotein.

Seventy natural and synthetic compounds were tested for potential to inhibit mutation induced by 7,12-dimethylbenz(a)anthracene (DMBA) in Salmonella typhimurium strain TM677. Results were compared with their ability to inhibit DMBA-induced preneoplastic lesions in a mouse mammary gland organ culture system. The response mediated by fifty-five of the test compounds was either positive or negative in both test systems, indicating that the combined use of these assays should aid in the discovery of antimutagenic agents that have cancer chemopreventive potential.

Three new biflavonoids to which we have accorded the trivial names calycopterone (1), isocalycopterone (2), and 4-demethylcalycopterone (3) and the known flavone 4',5-dihydroxy-3,3',6,7-tetramethoxyflavone (4) were isolated as cytotoxic constituents from the flowers of Calycopteris floribunda Lamk. (Combretaceae). Compounds 1-3 showed a wide range of activity against a panel of solid tumor cell lines. Among the biflavonoids, calycopterone (1) is the major constituent.

Brassinin, a phytoalexin, is found in Chinese cabbage. Previously, we showed that brassinin significantly inhibited dimethylbenz(a)anthracene (DMBA)-induced mammary lesions in organ culture. Moreover, it was an effective inhibitor against two stage skin carcinogenesis. In the present study, we synthesized several analogs of brassinin and evaluated their effectiveness in the mouse mammary gland organ culture model. Results showed that cyclobrassinin, also a naturally occurring brassinin analog, was more effective than brassinin. Spirobrassinin and N-ethyl-2,3-dihydrobrassinin also significantly inhibited mammary lesion formation. However, none of the methyl substituted analogs were effective. The effects of brassinin may, in part, be mediated by induction of phase II detoxifying enzymes such as quinone reductase.

Two pentacyclic triterpenes isolated from Maprounea africana, 1β-hydroxymaprounic acid 3-p-hydroxybenzoate [3], 2α-hydroxymaprounic acid 2,3-bis-p-hydroxybenzoate [4] and their respective hydrolyzed products [5] and [6] have been found to demonstrate potent inhibitory activity against HIV-1 reverse transcriptase