Aiming at overcoming multidrug resistance (MDR) in cancer, we have been studying Momordica balsamina, a vegetable known as African pumpkin. Five undescribed cucurbitane-type triterpenoids (balsaminaepoxide, bal-saminatriol, balsaminoic acid, balsaminal, and balsaminol G) along with five known cucurbitacins were isolated from the methanol extract of Momordica balsamina aerial parts, whose structures were elucidated by spectro-scopic data, mainly 1D and 2D NMR experiments. Compounds were evaluated for their ability as P-glycoprotein (P-gp/ABCB1) inhibitors in multidrug resistant human ABCB1-transfected mouse lymphoma cells (L5178Y, MDR) and resistant human colon adenocarcinoma cells (COLO 320), using the rhodamine-123 exclusion test, by flow cytometry. Several compounds, which were found to be non-cytotoxic, strongly inhibited P-gp efflux ac-tivity in a dose-dependent manner in both cell models. In MRD mouse lymphoma cells, balsaminol G and kar-avilagenin B were the most active, while in resistant colon adenocarcinoma cells, the strongest inhibitory activity was found for balsaminaepoxide, balsaminatriol and karavilagenin C, being several-fold more active than the positive control verapamil. In chemosensitivity assays, in a model of combination chemotherapy, selected compounds showed to interact synergistically with doxorubicin, thus substantiating their potential as MDR re-versers. The strongest synergistic interaction was found for balsaminal and balsaminol G.

Pistacia integerrima grows in some areas of Pakistan and some other south Asian countries such as Afghanistan, India, Nepal, and Myanmar. It is an important medicinal plant which has been traditionally used for the treatment of asthma, cough, and dysentery. In the present study, we intend to re-isolate bioactive compounds (I–III) from P. integerrima galls extracts. The chloroform extract was subjected to column chromatography that afforded three reported chemical constituents, 7-methoxynaringenin (I), 7-methoxy-3,5,7,4′-tetrahydroxyflavanone (II), and β-sitosterol (III). Compounds (I–III) were evaluated for multi-drug resistance (MDR) reversing effect by assessing their activity on various genes including transfected mouse gene, human mdrl gene, and transfected mouse T-lymphoma cell lines (L5178 and L5178Y). Compounds (I–III) exhibit significant dose-dependent MDR reversing effect against the T-lymphoma (mouse cell line). in-silico molecular docking investigations performed on compounds (I–III) showed a common binding site for these compounds and Rhodamine 123. Our findings indicated that the relative docking scores correlate satisfactorily with in vitro activities. It could be concluded that the inhibitory activity of compounds (I–III) is largely due to their interactions with the P-glycoprotein (P-gp). The present work could also contribute to the isolation of novel natural compounds that act as potent inhibitors for cancer treatment.

The bioactive triterpenoid 3-oxo-6-β-hydroxy-β-amyrin (1) has been isolated from multiple plant sources.In this study, chloroform fraction of Pistacia integerrima extract was processed for the isolation of the compound.The compound identity was confirmed by advanced spectroscopy technique.X-ray crystallography was applied for molecular structure confirmation.In addition, compound 1 was screen for its activity on reversal of MDR (multidrug resistance) mediated by P-gp (P-glycoprotein).This was accomplished by using rhodamine123 exclusion on multidrug-resistant human ABCB1 gene transfected mouse T-lymphoma cell line.Outcomes revealed that MDR reversing effect was comparable to verapamil as positive control in vitro.Treatment of TPA-induced tumor promotion with 3-oxo-6β-hydroxy-β-amyrin led to reduction in the applied anti-tumor promotion experiment.The chemo-preventive effect of 3-oxo-6β-hydroxy-βamyrin was comparable to curcumin as positive control based on the reduction of immediate early tumor antigen expression.Molecular docking by applying Autodock Vina 1 and i-GEMDOCK v 2.1 tools indicated that compound 1 gives good docking results, as determined by their fitness score and specificity.Moreover, results showed that compound 1 isolated from Pistacia integerrima precisely attached to a region where co-crystallized ligand for receptor previously existed.Our findings may explain the use of Pistacia integerrima plant extracts as an anticancer agent in folk medicine.

Bacteria often show resistance against antibiotics due to various mechanisms such as the expression of efflux pumps, biofilm formation, or bacterial quorum sensing (QS) controls. For successful therapy, the discovery of alternative agents is crucial. The objective of this study was to evaluate the efflux pump, anti-biofilm, and QS inhibiting, as well as antibacterial effects of 2-trifluoroacetonylbenzoxazole ligands (1-3) and their metal complexes (4-12) in bacteria. The ligand 2 and its Zn(II) complex 5, and furthermore the Cu(II) complex 7 of ligand 1, exerted remarkable antibacterial activity on the Staphylococcus aureus 272123 (MRSA) strain. In the minimum inhibitory concentration (MIC) reduction assay the ligand 3, the Zn(II) complex 5 of ligand 2, and the Cu(II), Ni(II), Mg(II), Fe(III) complexes (7, 8, 9, 12) of ligand 1 enhanced the antibacterial activity of ciprofloxacin in MRSA. An increased ethidium bromide accumulation was detected for ligand 3 in MRSA while the Fe(III) complex 12 of ligand 1 decreased the biofilm formation of the reference S. aureus ATCC 25923 strain. The Zn(II) and Ag(II) complexes (3 and 4) of ligand 1 and ligand 3 inhibited the QS. Based on our results, the ligands and their metal complexes could be potential alternative drugs in the treatment of infectious diseases.

Multidrug resistance (MDR) of cancer cells is a major cause of therapeutic failure. One of the mechanisms of MDR is the overexpression of efflux pump such as ABCB1. The use of ABCB1 inhibitors constitute an important strategy for reversing MDR. Thus, this study aimed to synthesize a novel 2-oxo-1,2-dihydroquinoline-4-carboxylic acid derivatives and evaluate their biological activities in vitro using parental (PAR) and multidrug resistant (MDR; ABCB1-overexpressing) mouse T-lymphoma cells. The cytotoxic activity and selectivity of the tested compounds were assessed by MTT method. The ABCB1 modulating activity was measured by rhodamine 123 accumulation assay using flow cytometry. The results showed that the compounds 2b, 2c and 3b exerted cytotoxic activity with IC50MDR value of 9.09 μM, 71.14 μM and 19.09 μM, respectively. The most active compound 8c should be considered as a lead compound for further derivatization and additional biological assays.

Multidrug resistance (MDR) that occurs in cancer cells constitutes one of the major reasons for chemotherapy failure. The main molecular mechanism of MDR is overexpression of protein transporters from the ATP-binding cassette (ABC) superfamily, such as ABCB1 (multidrug resistance protein 1 (MDR1), P-glycoprotein). At the expense of ATP hydrolysis, ABCB1 pumps a diverse range of substrates (including anticancer drugs) out of the cell, thereby reducing their intracellular concentration. In the present study, the ability of two patented disiloxanes (SILA-409 and SILA-421) to reverse drug resistance in human colon adenocarcinoma cell lines LoVo and LoVo/Dx was investigated. It was demonstrated that both compounds in concentrations of 0.5–1 µM strongly increased the sensitivity of LoVo/Dx cells to doxorubicin. By means of an accumulation test in which rhodamine 123 was used as an ABCB1 substrate analogue, both organosilicon compounds were also shown to inhibit ABCB1 transport activity. The intracellular accumulation of doxorubicin was also increased, and more drug entered the cellular nuclei of resistant cells in the presence of the studied compounds. In conclusion, both SILA-409 and SILA-421 were demonstrated to be effective MDR reversal agents in resistant human colon cancer cells.

The aim of current study was to explore crude extracts and various fractions of title plant for reversal of multi-drug resistance and anti-proliferative activities in mouse lymphoma cells. The extracts and its fractions were screened for the reversal of MDR of mouse lymphoma cell line transfected by ABCB1 gene and then the intracellular accumulation of rhodamine 123 (an analogue of epirubicine; a fluorescent substrate) was measured by flow cytometry. The transporter modulating potential of ABCB1 gene was evaluated by the fluorescence activity ratio (FAR) value. In the flow cytometry, the values of FSC (forward scatter count) and SSC (side scatter count) were increased indicating that the test samples have membrane effect due to which the granulation of cytoplasm was increased. All the test samples were screened at two different concentrations (2 and 20µg/ml) on MDR mouse lymphoma cells. The result showed that at low concentration (2µg/ml) only the CHCl 3 fraction (FAR=21.79) was more effective MDR modulator while the remaining test samples were less active. At high concentration (20µg/ml), the CHCl 3 fraction (FAR=68.91) was more effective followed by the EtOAc (FAR=23.42) and n -hexane (FAR=16.25) fractions. Rest of the test samples showed low effect in a short time experiment. The results showed that the EtOAc fraction has good anti-proliferative effect with IC 50 value of 12.33µg/ml followed by the CHCl 3 (IC 50 = 17.24µg/ml) and n -hexane (IC 50 = 17.32µg/ml) fractions on the mouse T-cell lymphoma. The remaining test samples showed low effect on the cells.

Introduction Macrocyclic diterpenes from Euphorbia species were found to be promising modulators of multidrug resistance (MDR), a complex phenomenon that hampers the effectiveness of cancer therapy. Objective To find new effective MDR reversers through the phytochemical study of E. boetica, including isolation and molecular derivatisation. Material and methods The phytochemical study of E. boetica was performed through chromatographic techniques. Preliminary analysis of crude chromatographic fractions from the methanol extract was carried out by H-1-NMR in order to prioritise the study of those having macrocyclic diterpenes. Polyamide resin was used to remove chlorophylls. Molecular derivatisation of isolated compounds comprised hydrolysis, reduction and acylation reactions. The structural identification of compounds was performed through analysis of spectroscopic data, mainly one-dimensional- and two-dimensional-NMR. The MDR reversing activity was assessed using a combination of transport and chemosensitivity assays, in mouse lymphoma (L5178Y-MDR) and Colo320 cell models. Results The H-1-NMR study of crude fractions and application of a straightforward method to remove chlorophylls, allowed the effortless isolation of two lathyrane-type diterpenes in large amounts, including the new polyester, euphoboetirane B (1). Taking advantage of the chemical functions of 1, 13 new derivatives were prepared. Several compounds showed to be promising modulators of P-glycoprotein (P-gp), in resistant cancer cells. Most of the compounds tested revealed to interact synergistically with doxorubicin. Conclusion These results corroborate the importance of macrocyclic lathyrane diterpenes as effective lead compounds for the reversal of MDR.

The number of effective antituberculotic drugs is strongly limited to four first-line drugs in standard therapy. In case of resistances second-line antibiotics are used with a poor efficacy and tolerability. Therefore, novel antituberculotic drugs are urgently needed. We synthesized novel nonclassical 1,4-dihydropyridines and evaluated their antituberculotic properties depending on substituent effects. Preferred substituents could be identified. As related classical 1,4-dihydropyridines are known as inhibitors of the transmembrane efflux pump ABCB1 in cancer cells, we wondered whether a use of our compounds may be of favour to enhance the antituberculotic drug efficacy of the second-line antituberculotic drug clofazimine, which is a known substrate of ABCB1 by a suggested inhibition of a corresponding efflux pump in Mycobacterium tuberculosis (Mtb). For this, we determined the ABCB1 inhibiting properties of our compounds in a mouse T-lymphoma cell line model and then evaluated the drug-enhancing properties of selected compounds in a co-application with clofazimine in our Mtb strain. We identified novel enhancers of clofazimine toxicity which could prevent clofazimine resistance development mediated by an efflux pump activity.

BACKGROUND/AIM:Multidrug resistance (MDR) represents a significant impediment to successful cancer treatment. In this study, novel metal [Zn(II), Cu(II), Mg(II), Ni(II), Pd(II), and Ag(I)] complexes of 2-trifluoroacetonylbenzoxazole previously synthesized and characterized by our group were tested for their MDR-reversing activity in comparison with the free ligands in L5178Y mouse T-lymphoma (MDR) cells transfected with human ATP-binding cassette sub-family B member 1 (ABCB1; P-glycoprotein) gene.MATERIALS AND METHODS:Cytotoxic and antiproliferative effects of the complexes were assessed by the thiazolyl blue tetrazolium bromide (MTT) method. Modulation of ABCB1 activity was measured by rhodamine 123 accumulation assay using flow cytometry. The apoptosis-inducing activity of some complexes was also tested on the multidrug resistant L5178Y mouse T-lymphoma cells, using the annexin-V/propidium iodide assay.RESULTS:When compared to the free ligand, a remarkable enhancement in MDR reversal and cytotoxic activity was found for the Zn(II) and Cu(II) complexes. The activity of the complexes proved to be up to 29- and 5-fold higher than that of the ligands and the ABCB1 inhibitor verapamil as positive control, respectively. The complexes possessed a remarkable potential to induce apoptosis of MDR cells.CONCLUSION:Our results suggest that the Zn(II) and Cu(II) complexes display significant MDR-reversing activity in a dose-dependent manner and possess strong cytotoxic activity and a remarkable potential to induce apoptosis in MDR L5178Y mouse T-lymphoma cells.

The number of effective first-line antibiotics for the treatment of Mycobacterium tuberculosis infection is strongly limited to a few drugs. Due to emerging resistance against those drugs, second- and third-line antibiotics have been established in therapy with certain problems and also increasing mycobacterial resistance. An alternative to such novel drugs or combined therapeutic regimes which may reduce resistance development is finding enhancers of mycobacterial drug effectiveness, especially enhancers that counteract causative resistance mechanisms. Such enhancers may reduce the extracellular drug efflux mediated by bacterial efflux pumps and thus enhance the intracellular drug toxicity. We developed novel 1,4-dihydropyridines (DHPs) as potential efflux pump inhibitors with some determined P-gp affinities. The influence on the antituberculotic drug toxicity has been investigated for three prominent antituberculotic drugs. Exclusive and selective toxicity enhancing effects have been detected for isoniazid (INH) which could be related to certain substituent effects of the 1,4-DHPs. So, structure-dependent activities have been found. Thus, promising enhancers could be identified and a suggested efflux pump inhibition is discussed.

The leaves of mini kiwi (Actinidia arguta) are a rich source of phenolic compounds, in particular the B-type procyanidins that exhibit e.g. antioxidant, anticancer, antiviral, and anti-inflammatory activities. The aim of this study was to determine the biological activity of the extract from leaves of kiwi in relation to cells of erythrocytes and lymphoma. This activity was determined by studying kiwi leaves extract anti-hemolytic, cytotoxic and antiproliferative activity, and its ability to change the physical properties of the cell membrane and inhibit multidrug resistance of mouse lymphoma cells. It was shown that the extract ingredients bound to the cells, caused changes in erythrocyte shape and slightly affected the granularity and size of lymphoma cells. They effectively protected the red blood cells from oxidative damage, but were not toxic to lymphoma cells and did not affect their multidrug resistance. The extract of kiwi leaves is an effective antioxidant but it does not exhibit cytotoxic activity. Therefore, it can be used in the prevention of diseases, especially those related to oxidative stress.

Background/Aim: Failure of cancer chemotherapy caused by multidrug resistance (MDR) of tumor cells is mediated by ABC transporters that reduce the uptake of cytotoxic agents. Similar transporters are responsible for amyloid clearance in nerve cells in Alzheimer's disease (AD). The aim of this study was to compare the biological effects of amyloid complexes of some known ABC transporter inhibitors e.g. disiloxanes. One of the most active fragments of the pathological “endogen” substrate responsible for AD was investigated in the presence of amyloid-beta fragment on the reversal of multidrug resistance and apoptosis induction on multidrug-resistant tumor cells in model experiments. Materials and Methods: The efflux pump activity of the cells treated with amyloid-beta complexes was studied by Rhodamin-123 accumulation. Apoptosis induction was measured by staining of treated cells by Annexin-V and propidium iodine. The fluorescent activity FL-1 and FL-2 of the cells was measured and analyzed on a PARTEC FACScan instrument. Results: The resistance modifiers: disiloxanes and memantine complexed with amyloid-beta 1-42 reduced the activity of ABC transporter in MDR tumor cells. Early apoptosis was moderately increased by amyloid-beta complexes. Late apoptosis and the number of total viable cells were not changed. Conclusion: Amyloid-beta and its complexes inactivate the efflux pump of tumor cells resulting in accumulation of amyloid. It is supposed that reduced membrane transport can explain the lower incidence of cancer in AD.

Background/Aim: Malignant diseases present a significant public health burden worldwide and their treatment is further complicated by the phenomenon of multidrug resistance. Derivatives of imidazopyridine exhibit several remarkable pharmacological activities and they could reverse the multidrug resistance of cancer cells due to overexpressing P-glycoprotein. Materials and Methods: A series of novel imidazo[4,5-b]pyridine derivatives were synthesized and their biological activities were evaluated in vitro using parental (PAR) and multidrug resistant (MDR; ABCB1-overexpressing) mouse T-lymphoma cells. The cytotoxic activity and selectivity of the tested compounds were assessed by the thiazolyl blue tetrazolium bromide (MTT) assay, the ABCB1 modulating activity was measured by rhodamine 123 accumulation assay using flow cytometry. Results: Six compounds (b, c, d, f, h and i) showed moderateto-high cytotoxic activity on the tested cell lines, while derivative i presented with promising selectivity towards the MDR cell line. Derivatives a, d, f, g and i were proven to be effective modulators of the ABCB1 multidrug efflux pump, with two compounds showing efflux pump modulatory activity at 2 mu M concentration. Conclusion: Based on our experimental results, compounds that showed potent activity are those with a short carbon side chain; a methoxy group on the benzene ring; a heterocyclic (triazole) side chain and the presence of an alkylated N-atom at position 4.

A dimeric naphthoquinone namely dihydrodyspyrole R (1) was purified once more from Diospyros lotus. Dihydrodyspyrole R and chloroform fractions were evaluated for their effects on the reversion of multidrug resistance (MDR). The compounds (1) and extract exhibited promising MDR reversing effect in a dose-dependent manner against mouse T-lymphoma cell line. Molecular docking of compound 1 revealed the correlation between in-silico with in-vitro results. The molecular docking results showed that compound 1 is bind closely where co-crystal ligand of P-gp is present. But usually, computational investigation predicts that, if a compound gives lesser score then compound will exhibit good activity. Hence, the docking scores of compound 1 are the near to the Rhodamine. It is conclude that there are certain important structural features of compound 1 which are responsible for the inhibiting potency of P-gp from mice. The computational Petra/Osiris/Molinspiration (POM) analysis confirms the possibility of use of compound 1 without side effect or less toxicity risks.

There is a complex interplay between the structural and other physicochemical properties of new compounds and the molecules in living organisms.

The phytochemical study of Euphorbia pedroi led to the isolation of a new tetracyclic triterpenoid with an unusual spiro scaffold, spiropedroxodiol (1), along with seven known terpenoids (2-8). Aiming at obtaining compounds with improved multidrug-resistance (MDR) reversal activity, compound 8, an ent-abietane diterpene, was derivatized by introducing nitrogen-containing and aromatic moieties, yielding compounds 9-14. The structures of compounds were characterized by detailed spectroscopic analysis, including 2D NMR experiments (COSY, HMQC/HSQC, HMBC, and NOESY). Compounds 1-14 were evaluated for their MDR-reversing activity on human ABCB1 gene transfected mouse lymphoma cells (L5178Y-MDR) through a combination of functional and chemosensitivity assays. The natural compounds 1-8 were further evaluated on resistant human colon adenocarcinoma cells (Colo320), and, additionally, their cytotoxicity was assessed on noncancerous mouse (NIH/3T3) and human (MRC-5) embryonic fibroblast cell lines. While spiropedroxodiol (1) was found to be a very strong MDR reversal agent in both L5178Y-MDR and Colo320 cells, the chemical modifications of helioscopinolide E (8) at C-3 positively contributed to increase the MDR reversal activity of compounds 10, 12, and 13. Furthermore, in combination assays, compounds 1 and 7-14 enhanced synergistically the cytotoxicity of doxorubicin. Finally, by means of molecular docking, the key residues and binding modes by which compounds 1-14 may interact with a murine P-glycoprotein model were identified, allowing additional insights on the efflux modulation mechanism of these compounds.

There is a constant need for new therapies against multidrug-resistant (MDR) cancer. Natural compounds are a promising source of novel anticancer agents. We recently showed that protoflavones display activity in MDR cancer cell lines that overexpress the P-glycoprotein (P-gp) drug efflux pump. In this study, 52 protoflavones, including 22 new derivatives, were synthesized and tested against a panel of drug-sensitive parental cells and their MDR derivatives obtained by transfection with the human ABCB1 or ABCG2 genes, or by adaptation to chemotherapeutics. With the exception of protoapigenone, identified as a weak ABCG2 substrate, all protoflavones bypass resistance conferred by these two transporters. The majority of the compounds were found to exhibit mild to strong (up to 13-fold) selectivity against the MCF-7(Dox) and KB-V1 cell lines, but not to transfected MDR cells engineered to overexpress the MDR transporters. Our results suggest that protoflavones can overcome MDR cancer by evading P-gp-mediated efflux.

Dregamine (1) and tabernaemontanine (2), two epimeric monoterpene indole alkaloids isolated in large amount from the roots of the African plant Tabernaemontana elegans, were derivatized, yielding ten imine derivatives, as previously described (3-12). In the present study, aiming at increasing the pool of analogues for establishing structure-activity relationships (SAR), compounds 1 and 2 were further submitted to several chemical transformations, yielding thirteen new derivatives (13-25). Their structures were assigned by spectroscopic methods, including 1D and 2D NMR experiments. Compounds 1-25 were evaluated for their effects on the reversion of multidrug resistance (MDR) in cancer cells mediated by P-glycoprotein (P-gp/ABCB1), through combination of functional and chemosensitivity assays, using a human ABCB1-transfected mouse T-lymphoma cell model. SAR analysis showed that different substituents at C-3 and at the indole nitrogen led to different ABCB1 modulatory effects. When compared to the parent compounds, a remarkable enhancement in MDR reversal activity was found for derivatives sharing a new aromatic moiety. Thus, the strongest ability as MDR reversers, and a manifold activity when compared to verapamil, was found for compound 8, the epimeric compounds 9 and 10, and compound 15, bearing pyrazine, bromo-pyridine, and methoxybenzyloxycarbonyl moieties, respectively. In drug combination assays, all compounds tested were revealed to interact synergistically with doxorubicin. Collectively, the results indicate that some of these derivatives may be promising leads for overcoming MDR in cancer.