Metabolic syndrome influences cardiac gene expression pattern at the transcript level in male ZDF rats.

BACKGROUND: Metabolic syndrome (coexisting visceral obesity, dyslipidemia, hyperglycemia, and hypertension) is a prominent risk factor for cardiovascular morbidity and mortality, however, its effect on cardiac gene expression pattern is unclear. Therefore, we examined the possible alterations in cardiac gene expression pattern in male Zucker Diabetic Fatty (ZDF) rats, a model of metabolic syndrome. METHODS: Fasting blood glucose, serum insulin, cholesterol and triglyceride levels were measured at 6, 16, and 25 wk of age in male ZDF and lean control rats. Oral glucose tolerance test was performed at 16 and 25 wk of age. At week 25, total RNA was isolated from the myocardium and assayed by rat oligonucleotide microarray for 14921 genes. Expression of selected genes was confirmed by qRT-PCR. RESULTS: Fasting blood glucose, serum insulin, cholesterol and triglyceride levels were significantly increased, glucose tolerance and insulin sensitivity were impaired in ZDF rats compared to leans. In hearts of ZDF rats, 36 genes showed significant up-regulation and 49 genes showed down-regulation as compared to lean controls. Genes with significantly altered expression in the heart due to metabolic syndrome includes functional clusters of metabolism (e.g. 3-hydroxy-3-methylglutaryl-Coenzyme A synthase 2; argininosuccinate synthetase; 2-amino-3-ketobutyrate-coenzyme A ligase), structural proteins (e.g. myosin IXA; aggrecan1), signal transduction (e.g. activating transcription factor 3; phospholipase A2; insulin responsive sequence DNA binding protein-1) stress response (e.g. heat shock 70kD protein 1A; heat shock protein 60; glutathione S-transferase Yc2 subunit), ion channels and receptors (e.g. ATPase, (Na+)/K+ transporting, beta 4 polypeptide; ATPase, H+/K+ transporting, nongastric, alpha polypeptide). Moreover some other genes with no definite functional clusters were also changed such as e.g. S100 calcium binding protein A3; ubiquitin carboxy-terminal hydrolase L1; interleukin 18. Gene ontology analysis revealed several significantly enriched functional inter-relationships between genes influenced by metabolic syndrome. CONCLUSIONS: Metabolic syndrome significantly alters cardiac gene expression profile which may be involved in development of cardiac pathologies in the presence of metabolic syndrome.

Carotenoids with anti-Helicobacter pylori activity from Golden delicious apple.

Previously it was reported that hypophasic carotenoids of Golden delicious apple peel showed potent anti-H. pylori activity (MIC(50) = 36 microg/mL), comparable to metronidazole (MIC(50) = 45 microg/mL). To further investigate the involved active carotenoids of the apple peel extracts, seven carotenoids were isolated for the current study: (all-E)-luteoxanthin, (all-E)-neoxanthin, (9'Z)-neoxanthin, (all-E)-antheraxanthin, (all-E)-violaxanthin, (9Z)-violaxanthin and (all-E)-lutein. The MIC(50) values of (all-E)-luteoxanthin, (all-E)-neoxanthin and (9'Z)-neoxanthin were 7.9, 11 and 27 microg/mL, respectively. Other carotenoids and beta,beta-carotene did not exhibit potent anti-H. pylori activity (MIC(50) > 100 microg/mL). An examination of structure and function suggested that active carotenoids contained a monofuranoid ring or an allenic bond in addition to an epoxy group and an additional two or three hydroxyl substituents on the side group.

Modelling of tumour--host coexistence In vitro in the presence of serine protease inhibitors.

The activities of cell surface serine proteases are markedly enhanced in malignant tumours. Proteolytic degradation of the extracellular matrix and basal membrane of normal cells is an important event for tumour cell growth and invasion. Two well-known broad-spectrum inhibitors of serine protease, Foy-305 and Ono-3403, were evaluated for their ability to affect the growth rate and survival of MCF7 breast cancer cells co-cultured with MRC5 lung fibroblasts as feeder cells in the absence of serum. Flow cytometry and differential staining demonstrated that in the mixed culture, the rate of tumor growth was dependent upon the presence of the feeder MRC5 lung fibroblasts and could be obviated by the additional presence of the inhibitors of serine proteases.

Inhibition of multidrug resistance of cancer cells by natural diterpenes, triterpenes and carotenoids.

The multidrug resistance (MDR) proteins are member of the ATP-binding cassette superfamily and are present in a majority of human tumors. Their activity is a crucial factor leading to therapeutic failure. It is likely that compounds which inhibit the function of the MDR-efflux proteins such as MDR1 will improve the cytotoxic action of anticancer chemotherapy. Therefore, a search for MDR reversing compounds was conducted among three classes of plant derived compounds such as diterpenes, triterpenes and carotenoids in a hope to find inhibitors without adverse effects in these natural compounds. The inhibition of efflux activity was determined by measuring the accumulation of substrate analogues such as rhodamine in tumor cells in the presence of potential inhibitors. Thus we determined the effect of structurally unrelated diterpenes, triterpenes and carotenoids on reversal of multidrug resistance in MDR-1 gene-transfected L1210 mouse lymphoma cells and MDR mediated multidrug resistance of human breast cancer cells MDA-MB-231 (HTB-26) and MCF-7. The majority of diterpenes, cycloartane triterpenes and carotenoids isolated from vegetables and medicinal plants were able to enhance rhodamine 123 accumulations of MDR-cells. Synergistic interaction was found between epirubicine and resistance modifier terpenoids in vitro. It is supposed that these MDR modulators bind into transmembrane domains and the action of ABC transporters is inhibited by induced conformational changes.

New potent P-glycoprotein inhibitors carrying a polycyclic scaffold.

New pentacyclic inhibitors of the P-glycoprotein carrying nitrogen-containing alkyl chains were synthesized and evaluated for MDR reverting activity on mouse lymphoma cells infected with pHa MDR1/A retrovirus. The activity of the compounds proved to be up to 5-fold higher than verapamil, used as reference compound.

Reversal of multidrug resistance of cancer cells in vitro: modification of drug resistance by selected carotenoids.

The development of multidrug resistance (MDR) causes difficulties in the chemotherapy of of human cancer. Investigation of the possibility of reversal of MDR has been greatly aided by the use of cell lines with acquired resitance to anticancer agents in vitro or transfected with the mdrl gene. The aim of this study was to examine new perspectives of chemotherapy focused on natural, carotenoid compounds, in connection with the modification of MDR. The function of the MDR protein was examined via the R123 drug accumulation of both cell lines in the presence of carotenoids. The fluorescence of the cell population was measured by flow cytometry. The most effective resistance modifiers Monoepoxy-beta-carotene, (SS, 8S)-capsochrome, (8'S) Luteoxanthin, (9Z)-Violaxanthin, (9Z)-Zeaxanthin, (13Z)-Zeaxanthin were assayed for their antiproliferative effects in combination with the anti-cancer drug epirubicin. (13Z)-Zeaxanthin was able to enhance the antiproliferative effect on human mdrl gene transfected mouse lymphoma and anthracycline resistant human breast cancer cell line MCF7. (8'S)-luteoxanthin, (5S, 8S)-capsochrome and (9Z)-zeaxanthin treatment revealed synergism with epirubicin on resistant mouse lymphoma. The enhanced antiproliferative activity of epirubicin combinated with (9Z)-Violaxanthin was more significant on MCF7 cells resistant to anthracycline.

Interaction between doxorubicin and the resistance modifier stilbene on multidrug resistant mouse lymphoma and human breast cancer cells.

The hydroxystilbene trans-3,5,3',4'-tetrahydroxystilbene (piceatannol) (1), isolated from the methanol extract of Euphorbia lagascae defatted seeds, was methylated to yield the derivatives trans-3,5,3',4'-tetramethoxystilbene (2), (trans-3,5-dihydroxy-3',4'-dimethoxystilbene) (3) and trans-3,5,3'-trihydroxy-4'-methoxystilbene (4). The structures of the compounds were assigned by spectroscopic methods (IR, 1H-NMR, 13C-NMR and MS). The ability of piceatannol (1) and the three methylated derivatives to modulate the transport activity of P-glycoprotein (P-gp) and apoptosis induction on the L5178 mouse lymphoma cell line containing the human MDR1 gene was studied by flow cytometry. The reversal of multidrug-resistance (MDR) was investigated by measuring the accumulation of rhodamine-123, a fluorescent substrate analog of doxorubicin, in cancer cells. Verapamil was applied as a positive control. For the evaluation of the compounds as apoptosis inducers, tumor cells were stained with FITC-labelled annexin-V and propidium iodide. The tetramethylated derivative (2) was found to be a powerful inhibitor of P-gp activity. Compounds 1 and 2 showed an increased apoptotic effect in the MDR subline, the most active being piceatannol (1). Furthermore, in the combination chemotherapy model, the interaction between doxorubicin and the resistance modifier 2 was studied in vitro. The results of checkerboard experiments indicated that the type of interaction was additive between doxorubicin and compound 2 on the human MDR1 gene-transfected mouse lymphoma cells. However, in the MCF7/dox human breast cancer cells, the interaction was non-additive. The degree of additive and non-additive interactions were close to the borderline of the FIX values corresponding to the two types of interactions.

Cinnamylidene ketones as potential modulators of multidrug resistance in mouse lymphoma and human colon cancer cell lines.

The resistance to chemotherapy of cancer cells is mediated by the overexpression of P-glycoprotein, as an ATP-dependent membrane efflux pump. Two families of compounds have been screened, the cinnamylidenecycloalkanones and cinnamylidenebenzocycloalkanones, as promising multidrug resistance (MDR) reversal agents on mouse lymphoma and human colon cancer (COL0320) cell lines. The antiproliferative effects of the cinnamylidene derivatives were tested with the MTT method The MDR effect on drug accumulation was tested by flow cytometry. Combinations of resistance modifiers and cytostatics were tested on the two cell lines to obtain evidence for additive or synergistic interactions. Verapamil was applied as a resistance-modifying positive control. The best effects in the reversal of MDR in both cell lines were exhibited by the methoxy derivatives 2-(2-methaoxycinnamylidene)indan-1-one, 2-(2-methoxycinnamylidene)-3,4-dihydro-2H-naphthalen-1-one, 6-(2-methoxycinnamylidene)-6,7,8,9-tetrahydrocyclohepten-5-one), 2-cinnamylidene-3,4-dihydro-2H-naphthalen-1-one and 6-cinnamylidene-6,7,8,9-tetrahydrobenzocyclohepten-5-one. 2-(2-methoxycinnamylidene) indan-1-one and 2-(2-methoxy-cinnamylidene)-3,4-dihydro-2H-naphthalen-1-one were able to enhance the antiproliferative activity of doxorubicin in a synergistic way.

Inhibition of P-glycoprotein transport activity in a resistant mouse lymphoma cell line by diterpenic lactones.

Multidrug resistance (MDR) is believed to be a major reason for the failure of cancer treatment. It is in most cases caused by the activity of the various ABC transporters, multidrug resistance (MDR) gene-encoded p-glycoproteins that pump anticancer drugs out of the cells. P-glycoprotein (P-gp) and multidrug resistance-associated protein (MRP1) are the most important and widely studied members of the ABC superfamily of transporters. The ability of four diterpenic lactones isolated from Euphorbia species to modulate the transport activity of P-gp in mouse lymphoma cells was evaluated by flow cytometry. The reversion of MDR was investigated by using a standard functional assay with rhodamine 123 as a fluorescent substrate analogue of doxorubicin. Verapamil was applied as a positive control. All the compounds were able to reverse the MDR of the tested human MDR1 gene-transfected mouse lymphoma cells, in a concentration-dependent manner from 4 to 40 microg/mL, in a short-term experiment below the cytotoxic doses.

The effects of jatrophane derivatives on the reversion of MDR1- and MRP-mediated multidrug resistance in the MDA-MB-231 (HTB-26) cell line.

Multidrug resistance (MDR) of cancer cells can be the result of a variety of mechanisms that are not completely understood. One of the most significant among them concerns altered membrane transport in tumor cells, often referred to as typical or classic MDR. This mechanism is related to the overexpression of a variety of proteins, that belong to the super family of ABC transporters. The aim or this study was to look for new effective modulators of MDR1 and multidrug resistance-associated protein (MRP) transporters. Ten diterpenes based on the jatrophane skeleton, including rearranged polycyclic derivatives, were studied on the MDA-MB-231 (HTB-26) human breast cancer cell line. The majority of those compounds were able to strongly enhance the rhodamine 123 accumulation of the human MDR1 gene transfected mouse lymphoma cell line, as previously described. In the present study, the MDR reversal of the same jatrophanes on MDR1- and MRP- mediated resistance of human breast cancer cells is reported. These cells simultaneously express MDR1 and MRP proteins when identified by monoclonal antibodies. However, in a functional assay, where rhodamine 123 accumulation was measured and verapamil was the traditional positive control, only MRP was active, while MDR1 was inactive. Carboxyfluorescein served as a substrate for MRP-mediated drug efflux, and indomethacine was the positive control used as an inhibitor of MRP in the flow cytometric experiments. The effectivity of various jatrophanes was different on the carboxyfluorescein efflux inhibition of the human breast cancer cells. These results may have importance in the planning of a new type of combination chemotherapy.

Modulation of multidrug resistance and apoptosis of cancer cells by selected carotenoids.

The multidrug resistance (MDR) proteins that belong to the ATP-binding casette superfamily are present in a majority of human tumors and are an important final cause of therapeutic failure. Therefore, compounds which inhibit the function of the MDR-efflux proteins may improve the cytotoxic action of anticancer chemotherapy. The effects of carotenoids were studied on the activity of the MDR-1 gene-encoded efflux pump system. The carotenoids, isolated from paprika and other vegetables, were tested on the rhodamine 123 accumulation of human MDR-1 gene-transfected L1210 mouse lymphoma cells and human breast cancer cells MDA-MB-231 (HTB-26). Capsanthin and capsorubin enhanced the rhodamine 123 accumulation 30-fold relative to nontreated lymphoma cells. Lycopene, lutein, antheraxanthin and violaxanthin had moderate effects, while alfa- and beta-carotene had no effect on the reversal of MDR in the tumor cells. Apoptosis was induced in human MDR1 transfected mouse lymphoma cells and human breast cancer MDA-MB-231 (HTB-26) cell lines in the presence of lycopene, zeaxanthin and capsanthin. The data suggest the potential of carotenoids as possible resistance modifiers in cancer chemotherapy.

Carotenoid composition and in vitro pharmacological activity of rose hips.

The aim of the present study was to compare carotenoid extracts of Rose hips (Rosa canina L.) with regard to their phytochemical profiles and their in vitro anti-Helicobacter pylori (H. pylori), cytotoxic, multidrug resistance (MDR) reversal and radical scavenging activity. Carotenoid composition was investigated in the different fractionation of rose hips, using extraction methods. Six main carotenoids - epimers of neochrome, lutein, zeaxanthin, rubixanthin, lycopene, ß,ß-carotene - were identified from Rose hips by their chromatographic behavior and UV-visible spectra, which is in accordance with other studies on carotenoids in this plant material. The active principles in the carotenoid extract might differ, depending upon the extraction procedures.

Interaction of tomato lectin with ABC transporter in cancer cells: glycosylation confers functional conformation of P-gp.

Phospho-glycoprotein (P-gp) is a polytopic plasma membrane protein whose overexpression causes multidrug resistance (MDR) responsible for the failure of cancer chemotherapy. P-gp 170 is a member of the ATP-binding cassette (ABC) transporter superfamily and has two potentially interesting regions for drugs interfering with its efflux function, namely the oligosaccharides on the first extracellular loop with unknown function and the two intracellular ATP-binding regions providing the energy for drug efflux function. The polylactoseamine oligosaccharides on the first loop can specifically bind the tomato lectin (TL). The P-gp efflux activities of TL-pre-treated MDR resistant cells were measured in the presence of structurally unrelated resistance modifiers such as phenothiazines, terpenoids and carotenoids. The inhibition of efflux activity was measured via the increased rhodamine uptake by mouse lymphoma cells transfected in human MDR1 gene and in human brain capillary endothelial cells. The tested resistance modifiers inhibit the function of ABC transporter resulting in increased R123 accumulation in MDR1 expressing cells. TL prevented the inhibitory action of phenothiazine and verapamil on brain capillary endothelial and MDR1-lymphoma cells, presumably due to the stabilization of the functional active conformation of P-gp. Our results indicate that the polylactosamine chains of P-gp are part of the functionally active protein conformation.

P-glycoprotein effects of cyclic urea HIV protease inhibitor DMP 323 in competitional absorption studies.

Cyclic ureas form a perspective class of non-peptidic HIV-1 protease inhibitors with major bioavailability problems. Low absorption rates of DMP 323 as one of the first representatives led to investigations whether transport efflux pump P-glycoprotein (P-gp) within the intestine may be partly responsible for the low absorption rates. DMP 323 proved to be a P-gp substrate in competition studies with P-gp inhibitor ritonavir and H17 as a representative of another class of non-peptidic HIV-1 protease inhibitors. Intestinal DMP 323 absorption was mainly increased under co-application of both ritonavir and H17. DMP 323 used as a membrane efflux pump inhibitor itself showed little affinities to P-gp compared to H17 as strong P-gp inhibitor. So P-gp proved to play a decisive role in the low intestinal absorption of the cyclic urea representative DMP 323.

New macrocyclic lathyrane diterpenes, from Euphorbia lagascae, as inhibitors of multidrug resistance of tumour cells.

The new macrocyclic lathyrane diterpenes latilagascenes A and B ( 1 and 2), the diacetylated derivative of 2, latilagascene C ( 3), and the known diterpenes ent-16alpha,17-dihydroxyatisan-3-one ( 4) and ent-16alpha,17-dihydroxykauran-3-one ( 5), isolated from the methanol extract of Euphorbia lagascae, were examined for their effects on the reversal of multidrug resistance (MDR) on mouse lymphoma cells. Among the active lathyrane derivatives 1 - 3, compound 2 displayed the highest inhibition of rhodamine 123 efflux of human MDR1 gene transfected mouse lymphoma cells when compared to the untreated cells or the positive control verapamil. The new compounds are the first macrocyclic lathyrane diterpenes showing oxidation at C-16, whose structures were characterized by extensive spectroscopic methods, including 2D NMR experiments ( (1)H- (1)H COSY, HMQC, HMBC and NOESY). The known phenolic compounds vanillic acid ( 6), p-salicylic acid ( 7), isofraxidin ( 8) and cleomiscosin A ( 9) were also isolated from this species.

Euphoportlandols A and B, tetracylic diterpene polyesters from Euphorbia portlandica and their anti-MDR effects in cancer cells.

Two new tetracyclic diterpene polyesters, euphoportlandols A (1) and B (2), have been isolated along with 12 known tetracyclic triterpenes from an acetone extract of Euphorbia portlandica. Their structures were established as 5alpha,11alpha,14alpha,17-tetraacetoxy-3beta-benzoyloxy-6beta,15beta-dihydroxy-9-oxoseget-8(12)-ene (1) and 5alpha,11alpha,14alpha,17-tetraacetoxy-3beta-benzoyloxy-6beta,15beta-dihydroxy-9-oxosegetane (2), respectively, by spectroscopic data interpretation. Compounds 1 and 2 were evaluated for their ability to inhibit multidrug resistance in cancer cells. Both compounds were found to be inhibitors of P-glycoprotein activity.

Biological activity of carotenoids in red paprika, Valencia orange and Golden delicious apple.

Carotenoid fractions were extracted from red paprika, Valencia orange peel and the peel of Golden delicious apple. Thus, hypophasic carotenoids of paprika (PM1), orange (PM3) and apple (PM4), and epiphasic extractions of paprika (PM2) and apple (PM5) were obtained by extraction, saponification and partition between MeOH-H(2)O (9:1) (hypophasic) and hexane (epiphasic). A high content of capsanthin was quantified in hypophasic carotenoids (PM1) from red spice paprika, whereas the hypophasic fractions from orange (PM3) and apple (PM4) were mainly composed of violaxanthin, zeaxanthin and lutein. On the other hand, a high content of beta,beta-carotene and beta-cryptoxanthin was found in epiphasic fractions (PM2 and PM5). The extracts were studied for their anti-Helicobacter pylori (H. pylori), anti-human immunodeficiency virus (HIV), cytotoxic, multidrug resistance (MDR) reversal and radical scavenging activity. Among five PM extracts and beta,betacarotene, PM4 showed potent anti-H. pylori activity (MIC(50) = 36 microg/mL), comparable to metronidazole (MIC(50) = 45 microg/mL). The extracts were inactive against HIV. PM3 and PM4 showed slightly higher cytotoxic activity against three human tumor cell lines (squamous cell carcinoma HSC-2, HSC-3, submandibular gland carcinoma HSG) and human promyelocytic leukemic HL-60 cells than against three normal human oral cells (gingival fibroblast HGF, pulp cell HPC, periodontal ligament fibroblast HPLF), suggesting a tumor-specific cytotoxic activity. PM1, PM3 and PM4 displayed much higher MDR-reversing activity than (+/-)-verapamil. ESR spectroscopy demonstrated that PM1-5 and beta,beta-carotene produced little or no detectable radical under alkaline conditions and did not scavenge the O(2) (-) produced by the hypoxanthine and xanthine oxidase reaction. On the other hand, PM1 and PM2 scavenged efficiently 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, whereas singlet oxygen was also quenched efficiently by PM5 and PM2. The data suggest the potential importance of carotenoids as possible anti-H. pylori and MDR reversal agents. The active principles in the carotenoid extract might differ, depending upon the types of fruits and vegetables.

Comparative effects on intestinal absorption in situ by P-glycoprotein-modifying HIV protease inhibitors.

PURPOSE: P-glycoprotein (P-gp) is made responsible for the limited oral bioavailability of P-gp substrates like peptidic HIV protease inhibitors (PIs). With respect to combined application of two PIs in antiretroviral regimes, we first investigated the influences on intestinal saquinavir uptake using different PIs in in situ perfusion studies. METHODS: Perfusion experiments were carried out in three intestinal segments with P-gp substrates talinolol and saquinavir using fixed concentrations of PIs and with each varying concentrations in the jejunum and ileum. Furthermore, cellular uptake of fluorescent P-gp substrate rhodamine-123 and MRP-substrate carboxyfluorescein has each been quantified in P-gp and MRP-expressing cells by flow cytometry under co-administration of PIs. RESULTS: Increase of calculated permeabilities of P-gp-specific substrate talinolol was found under co-administration of both PIs, ritonavir and H17, with highest absorption rates in the ileal and colon segment. H17 proved to be a better P-gp inhibitor than ritonavir by resulting IC50 values and also in the cellular uptake of rhodamine. Similar increases of permeabilities in ileum and colon have also been found for saquinavir as P-gp as well as MRP-substrate with differences in the jejunal uptake, which was found higher for H17. Additional MRP-inhibitory activities of H17 were proved by increasing cellular uptake rates of carboxyfluorescein in MRP-expressing cells. CONCLUSIONS: The investigated PIs were characterized as effective P-gp inhibitors in the intestinal absorption of P-gp substrates. H17 showed MRP-inhibitory effects that also favor intestinal drug absorption of corresponding substrates. With respect to combined therapeutic application of PIs, compounds like H17 raise hopes for improved bioavailability of poorly absorbed compounds.

Bacterial models for tumor development. Mini-review.

UNLABELLED: The tumor-inducing effects of Agrobacterium, Bartonella and Helicobacter bacterial species are compared step by step. An analogy for the existence of these individual steps is considered in connection with the development of cancer. The transformations of eukaryotic cells occur in particular in the type IV secretion system, i.e. involving the simultaneous transmission of DNA and protein from bacterial cells to eukaryotic cells. Thus, transfected cells facilitate the indefinite growth of tissue cells and additionally produce growth factors, triggering further bacterial multiplication. The higher numbers of bacteria then produce more transfection and the cycle repeats as long as the host lives. The main limiting factor is the frequency of bacterial infection, while the secondary rate-limiting factors are the levels of transforming growth factors and factors triggering bacteria growth. CONCLUSIONS: Analogous processes are probably responsible for the tumor induction by the three different bacterial species; however, the critical points for eradication are different. The early eradication or limitation of B. henselae or H. pylori can prevent hemangiomas, stomach cancer and malignant cell proliferation. The crown gall formation by A. tumefaciens can only be avoided by prevention of the transforming activity of a single bacterial infection. Questions arise as to what is common in the three processes, and the nature of the rate-limiting step in the three different models. The frequency of transformation is the rate-limiting step, but the co-transmission of the DNA-protein complex is common in the three systems.

Pubescenes, jatrophane diterpenes, from Euphorbia pubescens, with multidrug resistance reversing activity on mouse lymphoma cells.

The macrocyclic jatrophane diterpene polyesters, pubescenes A - D ( 1 - 4) were isolated from the whole dried plant of Euphorbia pubescens, and evaluated for multidrug resistance (MDR) reversing activity on mouse lymphoma cells. All the compounds displayed very strong activity compared with the positive control verapamil. Pubescene D ( 4) is a new compound, whose structure was established as 3beta,9alpha,-diacetoxy-7beta-benzoyloxy-15beta-hydroxy-14-oxo-2beta H-jatropha-5 E,12 E-diene by spectroscopic methods, including (1)H- (1)H COSY, HMQC, HMBC and NOESY.