The Amazon rain forest plant Uncaria tomentosa (cat's claw) and its specific proanthocyanidin constituents are potent inhibitors and reducers of both brain plaques and tangles.

Brain aging and Alzheimer's disease both demonstrate the accumulation of beta-amyloid protein containing "plaques" and tau protein containing "tangles" that contribute to accelerated memory loss and cognitive decline. In the present investigation we identified a specific plant extract and its constituents as a potential alternative natural solution for preventing and reducing both brain "plaques and tangles". PTI-00703 cat's claw (Uncaria tomentosa from a specific Peruvian source), a specific and natural plant extract from the Amazon rain forest, was identified as a potent inhibitor and reducer of both beta-amyloid fibrils (the main component of "plaques") and tau protein paired helical filaments/fibrils (the main component of "tangles"). PTI-00703 cat's claw demonstrated both the ability to prevent formation/aggregation and disaggregate preformed Aß fibrils (1-42 and 1-40) and tau protein tangles/filaments. The disaggregation/dissolution of Aß fibrils occurred nearly instantly when PTI-00703 cat's claw and Aß fibrils were mixed together as shown by a variety of methods including Thioflavin T fluorometry, Congo red staining, Thioflavin S fluorescence and electron microscopy. Sophisticated structural elucidation studies identified the major fractions and specific constituents within PTI-00703 cat's claw responsible for both the observed "plaque" and "tangle" inhibitory and reducing activity. Specific proanthocyanidins (i.e. epicatechin dimers and variants thereof) are newly identified polyphenolic components within Uncaria tomentosa that possess both "plaque and tangle" reducing and inhibitory activity. One major identified specific polyphenol within PTI-00703 cat's claw was epicatechin-4ß-8-epicatechin (i.e. an epicatechin dimer known as proanthocyanidin B2) that markedly reduced brain plaque load and improved short-term memory in younger and older APP "plaque-producing" (TASD-41) transgenic mice (bearing London and Swedish mutations). Proanthocyanidin B2 was also a potent inhibitor of brain inflammation as shown by reduction in astrocytosis and gliosis in TASD-41 transgenic mice. Blood-brain-barrier studies in Sprague-Dawley rats and CD-1 mice indicated that the major components of PTI-00703 cat's claw crossed the blood-brain-barrier and entered the brain parenchyma within 2 minutes of being in the blood. The discovery of a natural plant extract from the Amazon rain forest plant (i.e. Uncaria tomentosa or cat's claw) as both a potent "plaque and tangle" inhibitor and disaggregator is postulated to represent a potential breakthrough for the natural treatment of both normal brain aging and Alzheimer's disease.

The aryl hydrocarbon receptor as an antitumor target of synthetic curcuminoids in colorectal cancer.

BACKGROUND: Curcumin has proven to be a potent antitumor agent in both preclinical and clinical models of colorectal cancer (CRC). It has also been identified as a ligand of the transcription factor known as the aryl hydrocarbon receptor (AHR). Our laboratory has identified the AHR as a mechanism which contributes to both tumorigenesis in a mouse model of inflammatory CRC as well an apoptotic target in vitro. Curcumin's role as an AHR ligand may modulate its effects to induce colon cancer cell death, and this role may be enhanced via structural modification of the curcumin backbone. We sought to determine if the two piperidone analogs of curcumin, RL66 and RL118, exhibit more robust antitumor actions than their parent compound in the context of colorectal cancer in vitro. Moreover, to ascertain the ability of curcumin, RL66 and RL118 to activate the AHR and evaluate if this activation has any effect on CRC cell death. MATERIALS AND METHODS: DLD1, HCT116, LS513, and RKO colon cell lines were propagated in vitro. Natural curcumin was obtained commercially, whereas RL66 and RL118 were synthesized and characterized de novo. Multiwell fluorescent/luminescent signal detection was used to simultaneously ascertain cell viability, cell cytonecrosis, and relative amounts of apoptotic activity. AHR activity was measured with a dual luciferase reporter gene system. Stable expression of small interfering RNA interference was established in the HCT116 cell lines to create AHR "knock down" cell lines. RESULTS: Both RL66 and RL118 proved to be more potent antitumor agents than their parent compound curcumin in all cell lines tested. The majority of this cell death was due to induction of apoptosis, which occurred earlier and to a greater degree following RL66 and RL118 treatment as opposed to curcumin. Also, RL66 and RL118 were found to be activators of AHR, and a portion of their ability to cause cell death was dependent on this induction. Curcumin was found unable to activate the AHR, and levels of AHR messenger RNA did not change their effects on cell death. CONCLUSIONS: Piperidone analogs of curcumin exhibited enhanced antitumor effects in vitro as opposed to their parent compound. Even more, this enhanced cell death profile may be partially attributed to the ability of these compounds to activate the AHR. Further study of synthetic curcumin analogs as chemopreventives and chemoadjuncts in CRC is warranted. Also, more generally, the AHR may represent a potential putative target for novel anticancer agents for CRC.

A novel curcumin derivative increases the cytotoxicity of raloxifene in estrogen receptor-negative breast cancer cell lines.

There is a need for new, safe and efficacious drug therapies for the treatment of estrogen receptor (ER)-negative breast cancers. Raloxifene and the 2nd generation curcumin derivative 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) have been shown to inhibit the growth of ER-negative breast cancer cells in vitro and in vivo. We investigated whether RL91 could enhance the growth-suppressive effects mediated by raloxifene in MDA-MB-231, MDA-MB-468, Hs578t and SkBr3 human breast cancer cell lines. The cytotoxicity was consistent across the cell lines but RL91 was more potent. EC50 values for RL91 were 1.2-2 µM while EC50 values for raloxifene were 9.6-11.2 µM. When the cells were treated with raloxifene (15 µM), RL91 (1 µM) or a combination of the two for 6-72 h, the combination treatment consistently elicited significantly greater cytotoxicity compared to all other treatments. In SkBr3 cells the combination treatment caused significantly more cells to undergo G1 arrest compared to raloxifene. In all cell lines apoptosis was synergistically induced by the combination treatment, as shown by both flow cytometery and cleaved caspase-3. Furthermore, the stress kinase p38 was increased and EFGR isoforms were decreased by both raloxifene and raloxifene + RL91. The anti-angiogenic anti-metastatic potential of raloxifene was not increased by RL91, as MDA-MB-231 cell migration and invasion as well as endothelial tube formation by HUVEC cells was not different between raloxifene (10 µM) and the combination of raloxifene + RL91. Thus, our findings provide evidence that RL91 increases the ability of raloxifene to suppress ER-negative cancer cell growth by increasing the number of apoptotic cells. The broad effect of this drug combination across a range of ER-negative breast cancer cell lines indicates that this drug combination should be explored further in order to find a safe and efficacious therapy for ER-negative breast cancer.

Curcumin-derivative nanomicelles for the treatment of triple negative breast cancer.

BACKGROUND: Triple negative breast cancer (TNBC) is a subtype of breast cancer characterized by its poor outcome and a lack of targeted therapies. Recently, our laboratory has developed a second generation curcumin derivative, 3,5-bis(3,4,5-trimethoxybenzylidene)-1-methylpiperidine-4-one (RL71) that shows potent in vitro cytotoxicity. RL71 is hydrophobic with poor bioavailability which limits its clinical development. PURPOSE: We have designed styrene-co-maleic acid (SMA) micelles encapsulating 5, 10 or 15% RL71 by weight/weight ratio to improve its solubility and pharmacokinetic profile. METHODS: The micelles charge, size and release rate were characterized. We evaluated their cytotoxicity against TNBC cell lines. The internalization of the drug inside the cells was measured by HPLC and the efficiency of the micelles was tested using a tumor spheroid model. RESULTS: The micelles exhibited mean diameters of 125-185 nm and had a neutral charge. SMA-RL71 micelles have a cytotoxicity profile comparable to the free drug against several TNBC cell lines. Moreover, the 15% loaded micelles increased the stability of RL71 and demonstrated higher activity in a tumor spheroid model. CONCLUSION: The current study demonstrates the efficiency of SMA for drug delivery, the influence of physicochemical characteristics on cytotoxicity, and provides the basis for preclinical testing in vivo.

Re-directing an alkylating agent to mitochondria alters drug target and cell death mechanism.

We have successfully delivered a reactive alkylating agent, chlorambucil (Cbl), to the mitochondria of mammalian cells. Here, we characterize the mechanism of cell death for mitochondria-targeted chlorambucil (mt-Cbl) in vitro and assess its efficacy in a xenograft mouse model of leukemia. Using a ρ° cell model, we show that mt-Cbl toxicity is not dependent on mitochondrial DNA damage. We also illustrate that re-targeting Cbl to mitochondria results in a shift in the cell death mechanism from apoptosis to necrosis, and that this behavior is a general feature of mitochondria-targeted Cbl. Despite the change in cell death mechanisms, we show that mt-Cbl is still effective in vivo and has an improved pharmacokinetic profile compared to the parent drug. These findings illustrate that mitochondrial rerouting changes the site of action of Cbl and also alters the cell death mechanism drastically without compromising in vivo efficacy. Thus, mitochondrial delivery allows the exploitation of Cbl as a promiscuous mitochondrial protein inhibitor with promising therapeutic potential.

Anti-leukemic activity of ubiquinone-based compounds targeting trans-plasma membrane electron transport.

Trans-plasma membrane electron transport (tPMET) is a ubiquinone-dependent cell survival pathway for maintaining intracellular redox homeostasis in rapidly dividing cells. To target this pathway, fifteen ubiquinone-based compounds were designed and synthesized to position at the plasma membrane and disrupt tPMET. We established that quaternary ammonium salt moieties carrying highly hindered, positive electronic charges located to the plasma membrane. A ten-carbon chain linked to these moieties was effective at positioning the redox-active ubiquinone-like function within the lipid bilayer to disrupt tPMET in human leukemic cells (IC50 9 ± 1 µM). TPMET inhibition alone was not sufficient to induce significant cell death, but positively charged compounds could also enter the cell and disrupt intracellular redox balance, distinct from their effects on mitochondrial electron transport. The synergistic effect of tPMET inhibition plus intracellular redox disruption gave strong antiproliferative activity (IC50 2 ± 0.2 µM). Positively charged ubiquinone-based compounds inhibit human leukemic cell growth.

Unusual immuno-modulatory triterpene-caffeates in the skins of russeted varieties of apples and pears.

Three triterpene-caffeates have been isolated from skins of a russeted apple cultivar "Merton Russet" and identified by LC-MS and NMR as betulinic acid-3-cis-caffeate, betulinic acid-3-trans-caffeate, and oleanolic acid-3-trans-caffeate. Betulinic acid-3-trans-caffeate and oleanolic acid-3-trans-caffeate were also found in russeted pear skins. These compounds have not been previously reported in apples or pears, or in any other foods. Their presence was related to suberized tissue as they were only found in russet portions of the partially russeted apple cultivar "Cox's Orange Pippin" and were not detected in the waxy apple cultivar "Royal Gala". High concentrations of betulinic acid-3-trans-caffeate were found in the bark of both "Merton Russet" and "Royal Gala" trees. The three triterpene-caffeates showed anti-inflammatory activity in vitro, inhibiting NF-κB activation with IC50's of 6-9 µM. Betulinic acid-3-trans-caffeate, the predominant compound in the apples, was immuno-modulatory at around 10 µM in the in vitro and ex vivo bioassays, boosting production of the pro-inflammatory cytokine TNFα in cells stimulated with bacterial lipopolysaccharides.

Curcumin and synthetic analogs induce reactive oxygen species and decreases specificity protein (Sp) transcription factors by targeting microRNAs.

BACKGROUND: Curcumin inhibits growth of several cancer cell lines, and studies in this laboratory in bladder and pancreatic cancer cells show that curcumin downregulates specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and pro-oncogenic Sp-regulated genes. In this study, we investigated the anticancer activity of curcumin and several synthetic cyclohexanone and piperidine analogs in colon cancer cells. METHODS: The effects of curcumin and synthetic analogs on colon cancer cell proliferation and apoptosis were determined using standardized assays. The changes in Sp proteins and Sp-regulated gene products were analysed by western blots, and real time PCR was used to determine microRNA-27a (miR-27a), miR-20a, miR-17-5p and ZBTB10 and ZBTB4 mRNA expression. RESULTS: The IC50 (half-maximal) values for growth inhibition (24 hr) of colon cancer cells by curcumin and synthetic cyclohexanone and piperidine analogs of curcumin varied from 10 µM for curcumin to 0.7 µM for the most active synthetic piperidine analog RL197, which was used along with curcumin as model agents in this study. Curcumin and RL197 inhibited RKO and SW480 colon cancer cell growth and induced apoptosis, and this was accompanied by downregulation of specificity protein (Sp) transcription factors Sp1, Sp3 and Sp4 and Sp-regulated genes including the epidermal growth factor receptor (EGFR), hepatocyte growth factor receptor (c-MET), survivin, bcl-2, cyclin D1 and NFκB (p65 and p50). Curcumin and RL197 also induced reactive oxygen species (ROS), and cotreatment with the antioxidant glutathione significantly attenuated curcumin- and RL197-induced growth inhibition and downregulation of Sp1, Sp3, Sp4 and Sp-regulated genes. The mechanism of curcumin-/RL197-induced repression of Sp transcription factors was ROS-dependent and due to induction of the Sp repressors ZBTB10 and ZBTB4 and downregulation of microRNAs (miR)-27a, miR-20a and miR-17-5p that regulate these repressors. CONCLUSIONS: These results identify a new and highly potent curcumin derivative and demonstrate that in cells where curcumin and RL197 induce ROS, an important underlying mechanism of action involves perturbation of miR-ZBTB10/ZBTB4, resulting in the induction of these repressors which downregulate Sp transcription factors and Sp-regulated genes.

RL66 a second-generation curcumin analog has potent in vivo and in vitro anticancer activity in ER­negative breast cancer models.

There is a need for the development of new safe and efficacious drug therapies for the treatment of estrogen receptor (ER)­negative breast cancers. 1-Methyl-3,5-bis[(E)-4-pyridyl)methylidene]-4-piperidone (RL66) is a second generation curcumin analog that exhibits potent cytotoxicity towards a variety of ER-negative breast cancer cells. Therefore, we have further examined the mechanism of this novel drug in in vitro and in vivo models of ER-negative breast cancer. The mechanistic studies demonstrated that RL66 (2 µM) induced cell cycle arrest in the G2/M phase of the cell cycle. Moreover, RL66 (2 µM) caused 40% of SKBr3 cells to undergo apoptosis after 48 h and this effect was time-dependent. This correlated with an increase in cleaved caspase-3 as shown by western blot analysis. RL66 (2 µM) also decreased HER2/neu phosphorylation and increased p27 in SKBr3 cells, while in MDA-MB-231 and MDA-MB-468 cells RL66 (2 µM) significantly decreased Akt phosphorylation and transiently increased the stress kinases JNK1/2 and MAPK p38. In addition, RL66 exhibited anti-angiogenic potential in vitro as it inhibited HUVEC cell migration 46% and the ability of these cells to form tube­like networks. RL66 (8.5 mg/kg) suppressed the growth of MDA-MB-468 xenograft tumors by 48% compared to vehicle control following 10 weeks of daily oral administration. Microvessel density in the tumors from treated mice was also decreased 57% compared to control. Thus our findings demonstrate that RL66 has potent proapoptotic and anti-angiogenic properties in vivo and in vitro and has the potential to be further developed as a drug for the treatment of ER­negative breast cancer.

RL71, a second-generation curcumin analog, induces apoptosis and downregulates Akt in ER-negative breast cancer cells.

There is a need for the development of new, safe and efficacious drug therapies for the treatment of estrogen receptor (ER)-negative breast cancers. RL71 is a second-generation curcumin analog that exhibits potent cytotoxicity towards a variety of ER-negative breast cancer cells. Therefore, we have further examined the mechanism of this anticancer activity in three different ER-negative breast cancer cell lines. The mechanistic studies demonstrated that RL71 (1 µM) induced cell cycle arrest in the G2/M phase of the cell cycle. Moreover, RL71 (1 µM) caused 35% of SKBr3 cells to undergo apoptosis after 48 h and this effect was time-dependent. This correlated with an increase in cleaved caspase-3 as shown by western blotting. RL71 (1 µM) also decreased HER2/neu phosphorylation and increased p27 in SKBr3 cells. While in MDA-MB-231 and MDA-MB-468 cells RL71 (1 µM) significantly decreased Akt phosphorylation and transiently increased the stress kinases JNK1/2 and p38 MAPK. In addition, RL71 exhibited anti-angiogenic potential in vitro as it inhibited HUVEC cell migration and the ability of these cells to form tube-like networks. RL71 (8.5 mg/kg) was also orally bioavailable as it produced a peak plasma concentration of 0.405 µg/ml, 5 min after oral drug administration. Thus, our findings provide evidence that RL71 has potent anticancer activity and has potential to be further developed as a drug for the treatment of ER-negative breast cancer.

Identification of cyclohexanone derivatives that act as catalytic inhibitors of topoisomerase I: effects on tamoxifen-resistant MCF-7 cancer cells.

Breast cancer is commonly treated with anti-estrogens or aromatase inhibitors, but resistant disease eventually develops and new therapies for such resistance are of great interest. We have previously isolated several tamoxifen-resistant variant sub-lines of the MCF-7 breast cancer cell line and provided evidence that they arose from expansion of pre-existing minor populations. We have searched for therapeutic agents that exhibit selective growth inhibition of the resistant lines and here investigate 2,6-bis(pyridin-3-ylmethylene)-cyclohexanone (RL90) and 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91). We found that two of the tamoxifen-resistant sub-lines (TamR3 and TamC3) unexpectedly showed increased sensitivity to RL90 and RL91. We utilized growth inhibition assays, flow cytometry and immunoblotting to establish a mechanistic basis for their action. Treated sensitive cells showed S-phase selective DNA damage, as detected by histone H2AX phosphorylation. Cellular responses were similar to those induced by the topoisomerase I poison camptothecin. Although IC(50) values of camptothecin, RL90, RL91 were correlated, studies with purified mammalian topoisomerase I suggested that RL90 and RL91 differed from camptothecin by acting as catalytic topoisomerase I inhibitors. These drugs provide a platform for the further development of DNA damaging drugs that have selective effects on tamoxifen resistant breast cancer cells. The results also raise the question of whether clinical topoisomerase I poisons such as irinotecan and topotecan might be active in the treatment of some types of tamoxifen-resistant cancer.

The novel phloroglucinol PMT7 kills glycolytic cancer cells by blocking autophagy and sensitizing to nutrient stress.

The switch from oxidative phosphorylation to glycolytic metabolism results in cells that generate fewer reactive oxygen species (ROS) and are resistant to the intrinsic induction of apoptosis. As a consequence, glycolytic cancer cells are resistant to radiation and chemotherapeutic agents that rely on production of ROS or intrinsic apoptosis. Further, the level of glycolysis correlates with tumor invasion, making glycolytic cancer cells an important target for new therapy development. We have synthesized a novel redox-active quinone phloroglucinol derivative, PMT7. Toxicity of PMT7 was in part due to loss of mitochondrial membrane potential in treated cells with subsequent loss of mitochondrial metabolic activity. Mitochondrial gene knockout ρ0 cells, a model of highly glycolytic cancers, were only half as sensitive as the corresponding wild-type cells and metabolic pathways downstream of MET were unaffected in ρ0 cells. However, PMT7 toxicity was also due to a block in autophagy. Both wild-type and ρ0 cells were susceptible to autophagy blockade, and the resistance of ρ0 cells to PMT7 could be overcome by serum deprivation, a situation where autophagy becomes necessary for survival. The stress response class III deacetylase SIRT1 was not significantly involved in PMT7 toxicity, suggesting that unlike other chemotherapeutic drugs, SIRT1-mediated stress and survival responses were not induced by PMT7. The dependence on autophagy or other scavenging pathways makes glycolytic cancer cells vulnerable. This can be exploited by induction of energetic stress to specifically sensitize glycolytic cells to other stresses such as nutrient deprivation or potentially chemotherapy.

Mechanisms for the activity of heterocyclic cyclohexanone curcumin derivatives in estrogen receptor negative human breast cancer cell lines.

Estrogen receptor (ER)-negative breast cancer is an aggressive form that currently requires more drug treatment options. Thus, we have further modified cyclohexanone derivatives of curcumin and examined them for cytotoxicity towards ER-negative human breast cancer cells. Two of the analogs screened elicited increased cytotoxic potency compared to curcumin and other previously studied derivatives. Specifically, 2,6-bis(pyridin-3-ylmethylene)-cyclohexanone (RL90) and 2,6-bis(pyridin-4-ylmethylene)-cyclohexanone (RL91) elicited EC(50) values of 1.54 and 1.10 µM, respectively, in MDA-MB-231 cells and EC(50) values of 0.51 and 0.23 in SKBr3 cells. All other new compounds examined were less potent than curcumin, which elicited EC(50) values of 7.6 and 2.4 µM in MDA-MB-231 and SKBr3 cells, respectively. Mechanistic analyses demonstrated that RL90 and RL91 significantly induced G(2)/M-phase cell cycle arrest and apoptosis. RL90 and RL91 also modulated the expression of key cell signaling proteins, specifically, in SKBr3 cells, protein levels of Her-2, Akt, and NFκB were decreased in a time-dependent manner, while activity of stress kinases JNK1/2 and P38 MAPK were increased. Signaling events in MDA-MB-231 cells were differently implicated, as EGFR protein levels were decreased and activity of GSK-3ß transiently decreased, while ß-catenin protein level and activity of P38 MAPK, Akt, and JNK1/2 were transiently increased. In conclusion replacement of the phenyl group of cyclohexanone derived curcumin derivatives with heterocyclic rings forms a class of second-generation analogs that are more potent than both curcumin and other derivatives. These new derivatives provide a platform for the further development of drugs for the treatment of ER-negative breast cancer.

Synthesis and cytotoxic potential of heterocyclic cyclohexanone analogues of curcumin.

A series of 18 heterocyclic cyclohexanone analogues of curcumin have been synthesised and screened for their activity in both adherent and non-adherent cancer cell models. Cytotoxicity towards MBA-MB-231 breast cancer cells, as well as ability to inhibit NF-kappaB transactivation in non-adherent K562 leukemia cells were investigated. Three of these analogues 3,5-bis(pyridine-4-yl)-1-methylpiperidin-4-one B1, 3,5-bis(3,4,5-trimethoxybenzylidene)-1-methylpiperidin-4-one B10, and 8-methyl-2,4-bis((pyridine-4-yl)methylene)-8-aza-bicyclo[3.2.1]octan-3-one C1 showed potent cytotoxicity towards MBA-MB-231, MDA-MB-468, and SkBr3 cell lines with EC50 values below 1 microM and inhibition of NF-kappaB activation below 7.5 microM. The lead drug candidate, B10, was also able to cause 43% of MDA-MB-231 cells to undergo apoptosis after 18 h. This level of activity warrants further investigation for the treatment of ER-negative breast cancer and/or chronic myelogenous leukemia as prototypical cellular models for solid and liquid tumors.

An antiproliferative bis-prenylated quinone from the New Zealand brown alga Perithalia capillaris.

Bioactivity-directed isolation work on the endemic New Zealand brown alga Perithalia capillaris, seeking anti-inflammatory compounds, led to a new bis-prenylated quinone ( 4). This compound inhibited superoxide production by human neutrophils in vitro (IC 50 2.1 microM), but was more potent at inhibiting proliferation of HL60 cells (IC 50 0.34 microM). Two related bis-prenylated phenols were also isolated, one known ( 2) and one new ( 5), with weaker biological activities. This report extends the examples of bis-prenylated phenols as chemotaxonomic markers for brown algae of the order Sporochnales.

Potential mechanisms for the synergistic cytotoxicity elicited by 4-hydroxytamoxifen and epigallocatechin gallate in MDA-MB-231 cells.

Potential mechanisms for the synergistic cytotoxicity elicited by epigallocatechin gallate (EGCG) (25 microM) and 4-hydroxytamoxifen (4-OHT) (1 microM) in MDA-MB-231 human breast cancer cells were investigated. The role of apoptosis was determined using chromatin condensation and Annexin-V staining. Condensed chromatin was visible following 24 h of combination treatment while flow cytometry experiments demonstrated that apoptosis was 2-fold greater following 36 h of combination treatment compared to EGCG. The temporal appearance of cells in G1-arrest did not correlate with apoptosis and thus was not considered to be a viable mechanism for the enhancement of apoptosis. While 4-OHT was a weak competitive inhibitor of microsomal UGT activity (Ki 95 microM), it did not alter the metabolism of EGCG as the rate of disappearance of EGCG from the media was the same for cells treated with either EGCG or EGCG + 4-OHT. Additionally, the metabolism of EGCG was not shifted toward the production of active methylated metabolites, as neither 4''-MeEGCG nor 4',4''-diMeEGCG (2.5-25 microM) were cytotoxic toward MDA-MB-231 cells. In conclusion, the synergistic cytotoxicity elicited by the combination of EGCG and 4-OHT results from an earlier induction of apoptosis but this was not caused by an increase in G1-arrest or 4-OHT-mediated changes in the metabolism of EGCG.

A cytotoxic triketone-phloroglucinol-bullatenone hybrid from Lophomyrtus bullata.

Cytotoxic activity against the P388 cell line was seen in a crude extract of the New Zealand shrub Lophomyrtus bullata(Myrtaceae). Bioactivity-guided isolation led to a compound with NMR spectra complicated by the presence of two isomers. These crystallised together and an X-ray structure showed them to be stereoisomeric hybrids of triketone, phloroglucinol and bullatenone units. NMR measurements on the mixed isomers, as well as a cyclic ether produced from them by acid catalysed dehydration, were consistent with these structures. The natural products, named bullataketals A and B, have cytotoxic activity against the P388 cell line (IC(50) 1 microg ml(-1)), and antimicrobial activity against Bacillus subtilis.