Antiproliferative activity and apoptosis induction by trijuganone C isolated from the root of Salvia miltiorrhiza Bunge (Danshen)

In this study, we found that the hexane fraction of Danshen, the dried root of Salvia miltiorrhiza (Lamiaceae), exerted antiproliferative effects on human leukemia cells. Phytochemical investigation of the hexane fraction achieved the isolation of the tanshinone diterpenes: dihydrotanshinone I ( 1 ), trijuganone C ( 2 ), trijuganone B ( 3 ), cryptotanshinone ( 4 ), tanshinone IIA ( 5 ), and tanshinone I ( 6 ). Compound 2 showed significant antiproliferative activities against human leukemia cells HL‐60, Jurkat, and U937. The antiproliferative activities of 2 against human cancer and normal cells indicated that 2 exhibited potent antiproliferative activities with IC₅₀ values less than 10 μM against HL‐60 and Jurkat cells as well as on the colon cancer cells DLD‐1, COLO 205, and Caco‐2. Compound 2 induced chromatin condensation, DNA fragmentation, activation of caspase‐3, ‐8, and ‐9, and the cleavage of poly (ADP‐ribose) polymerase (PARP) in HL‐60 cells. Moreover, 2 activated Bid and Bax, leading to the loss of mitochondrial membrane potential, and 2 induced the cytochrome c release from mitochondria into cytosol. In contrast, Bcl‐2 and Bcl‐xL were unaffected by 2 . These results suggest that 2 exerts antiproliferative effects via apoptosis induction mediated by mitochondrial dysfunction and caspase activation. Compound 2 may serve as a candidate of potential chemotherapeutic agent for human leukemia.     

补骨脂素对HL60/HT耐药细胞逆转及对细胞内Ca2+浓度影响研究

 目的研究补骨脂素对HL60/HT耐药细胞逆转作用及对耐药细胞内Ca²⁺浓度影响,探讨其可能作用机制。方法采用MTT法测定补骨脂素对细胞增殖抑制作用,高效液相色谱法检测细胞内HT的浓度,激光共聚焦显微镜测定细胞内不同时段和不同时间点的Ca²⁺浓度。结果补骨脂素在1～20μmol·L^-1能不同程度降低HT对HL60/HT细胞的IC50,并不同程度提高细胞内HT浓度;1～20μmol·L^-1补骨脂素在不同作用时段(24,48,96 h)对HL60/HT细胞内Ca2+浓度与作用时间成负相关,10～20μmol·L^-1补骨脂素在作用HL60/HT不同时间点(5,10,15,20,25 min)细胞内Ca2+浓度与作用时间成负相关性。结论补骨脂素能逆转HL60/HT细胞的MDR,其作用机制与影响耐药细胞内Ca²⁺浓度,故而增加细胞内HT浓度有关。     

Biological activities of xanthatin from Xanthium strumarium leaves

The objective of the present work was to evaluate the biological activities of the major bioactive compound, xanthatin, and other compounds from Xanthium strumarium (Asteraceae) leaves. Inhibition of bloodstream forms of Trypanosoma brucei brucei and leukaemia HL‐60 cell proliferation was assessed using resazurin as a vital stain. Xanthatin was found to be the major and most active compound against T. b. brucei with an IC₅₀ value of 2.63 µg/mL and a selectivity index of 20. The possible mode of action of xanthatin was further evaluated. Xanthatin showed antiinflammatory activity by inhibiting both PGE₂ synthesis (24% inhibition) and 5‐lipoxygenase activity (92% inhibition) at concentrations of 100 µg/mL and 97 µg/mL, respectively. Xanthatin exhibited weak irreversible inhibition of parasite specific trypanothione reductase. Unlike xanthatin, diminazene aceturate and ethidium bromide showed strong DNA intercalation with IC₅₀ values of 26.04 µg/mL and 44.70 µg/mL, respectively. Substantial induction of caspase 3/7 activity in MIA PaCa‐2 cells was observed after 6 h of treatment with 100 µg/mL of xanthatin. All these data taken together suggest that xanthatin exerts its biological activity by inducing apoptosis and inhibiting both PGE₂ synthesis and 5‐lipoxygenase activity thereby avoiding unwanted inflammation commonly observed in diseases such as trypanosomiasis. Copyright © 2011 John Wiley & Sons, Ltd.     

Ethyl acetate fraction of the root of rubia cordifolia L. inhibits keratinocyte proliferation in vitro and promotes keratinocyte differentiation in vivo: potential application for psoriasis treatment

Psoriasis is a skin disease associated with hyperproliferation and aberrant differentiation of keratinocytes. Our previous studies have identified the root of Rubia cordifolia L. as a potent antiproliferative and apoptogenic agent in cultured HaCaT cells (IC₅₀ 1.4 μg/ml). In the present study, ethanolic extract of Radix Rubiae was fractioned sequentially with hexane, ethyl acetate (EA), n‐butanol and water. EA fraction was found to possess most potent antiproliferative action on HaCaT cells (IC₅₀ 0.9 μg/ml). Mechanistic study revealed that EA fraction induced apoptosis on HaCaT cells, as it was capable of inducing apoptotic morphological changes. Annexin V‐PI staining assay also demonstrated that EA fraction significantly augmented HaCaT apoptosis. In addition, EA fraction decreased mitochondrial membrane potential in a concentration‐ and time‐dependent manner. The standardized EA fraction was formulated into topical gel and its keratinocyte‐modulating action was tested on mouse tail model. EA fraction dose‐dependently increased the number and thickness of granular layer and epidermal thickness on mouse tail skin, indicative of the keratinocyte differentiation‐inducing activity. Taking the in vitro and in vivo findings together, the present preclinical study confirms that EA fraction is a promising antipsoriatic agent warranting further development for psoriasis treatment. Copyright © 2009 John Wiley & Sons, Ltd.     

A chemically characterized ethanolic extract of Thai Perilla frutescens (L.) Britton fruits (nutlets) reduces oxidative stress and lipid peroxidation in human hepatoma (HuH7) cells

Perilla frutescens is cultivated in East Asian countries including Thailand, and the nutlets (single‐seeded fruits) are used as traditional and medicinal food. Perilla nutlets extracted by ethyl acetate (EA), 80% ethanol (Eth), and hot water (HW) sequentially were chemically characterized using high‐resolution accurate liquid chromatography‐mass spectrometry with the main compounds detected assigned as rosmarinic acid and derivatives of the flavones apigenin and luteolin, with the more diverse chemical composition observed with the Eth extract. All extracts showed dose‐dependent free‐radical scavenging activity, with the Eth extract the most potent (IC₅₀ = 3.43 mg/ml for ABTS^? scavenging and 0.27 mg/ml for DPPH^? scavenging). The Eth extract also inhibited AAPH‐induced hemolysis (IC₅₀ = 0.07 mg/ml) more potently than did the HW (IC₅₀ = 0.38 mg/ml) and EA extracts (IC₅₀ = 1.63 mg/ml). An MTT test revealed all the extracts were noncytotoxic at concentrations up to 200 μg/ml. Only the Eth and EA extracts showed protective effects against the generation of reactive oxygen species and lipid peroxidation in FeCl₃‐induced HuH7 cells in a dose‐dependent manner. Our findings suggest the Eth extract of Thai perilla nutlets, containing rosmarinic acid and flavones and their derivatives, may have potential to provide protection against oxidative stress in hepatic disorders.     

Screening of some Tanzanian medicinal plants for their trypanocidal and cytotoxic activities

The objective of the present study was to evaluate in vitro antitrypanosomal and cytotoxic activities of crude extracts of 20 traditionally used medicinal plants of Tanzania. A total of 40 extracts (dichloromethane and methanol) were screened for antiproliferative activity of bloodstream form of T. b. brucei and human leukaemia HL‐60 cell. Inhibition of cell proliferation was assessed using resazurin as vital stain. Of the 40 extracts tested, the dichloromethane extract from bark of Warburgia salutaris (Canellaceae) exhibited the most potent antitrypanosomal activity with an IC₅₀ value of 10.68 μg/ml. A dichloromethane extract from Lannea stuhlmannii (Anacardiaceae) was found to be the most cytotoxic extract against HL‐60 (IC₅₀ = 27.15 μg/ml). Out of the 20 plants tested, 5 plants exhibited trypanocidal activity with IC₅₀ values below 20 μg/ml. These 5 plants: Entandrophragma bussei (Meliaceae), Securidaca longepedunculata (Polygalaceae), Warburgia salutaris (Canellaceae), Zanha africana (Sapindaceae) and Zanthoxylum chalybeum (Rutaceae) could therefore serve as sources of lead compounds for treatment of trypanosomiasis. Copyright © 2009 John Wiley & Sons, Ltd.     

Chebulinic Acid Isolated From the Fruits of Terminalia chebula Specifically Induces Apoptosis in Acute Myeloid Leukemia Cells

Chebulinic acid, an ellagitannin found in the fruits of Terminalia chebula, has been extensively used in traditional Indian system of medicine. It has shown to have various biological activities including antitumor activity. The present study aims to investigate the cytotoxic potential of chebulinic acid in human myeloid leukemia cells. Interestingly, chebulinic acid caused apoptosis of acute promyelocytic leukemia HL‐60 and NB4 cells but not K562 cells. In vitro antitumor effects of chebulinic acid were investigated by using various acute myeloid leukemia cell lines. Chebulinic acid treatment to HL‐60 and NB4 cells induced caspase activation, cleavage of poly(ADP‐ribose) polymerase, DNA fragmentation, chromatin condensation, and changes in the mitochondrial membrane permeability. Additionally, inhibition of caspase activation drastically reduced the chebulinic acid‐induced apoptosis of acute promyelocytic leukemia cells. Our data also demonstrate that chebulinic acid‐induced apoptosis in HL‐60 and NB4 cells involves activation of extracellular signal‐regulated kinases, which, when inhibited with ERK inhibitor PD98059, mitigates the chebulinic acid‐induced apoptosis. Taken together, our findings exhibit the selective potentiation of chebulinic acid‐induced apoptosis in acute promyelocytic leukemia cells. Copyright © 2017 John Wiley & Sons, Ltd.     

藤黄酸对急性白血病细胞U937增殖和凋亡的影响及对核孔蛋白Nup88的调控作用

目的 观察藤黄酸对白血病细胞株U937增殖和凋亡的影响及其对核孔蛋白Nup88的调控作用,研究藤黄酸诱导凋亡作用与其调节Nup88的相互关系.方法 采用MTT比色法检测细胞增殖活性,Annexin-V FITC/PI双标法及Hoechst 33258染色法分析细胞凋亡的改变,流式细胞术分析细胞周期和细胞内核孔蛋白Nup88的改变,RT-PCR检测藤黄酸对白血病细胞内Nupp88基因表达的调控作用;共聚焦显微镜观察Nup88蛋白的细胞分布情况.结果 藤黄酸能明显抑制U937细胞的增殖,其抑制作用呈时间、剂量依赖性,其24 h的IC50为(1.019±0.134)mg/L;此外,藤黄酸还具有诱导U937细胞凋亡和G0/G1期阻滞的作用.核孔蛋白Nup88弥漫分布于白血病细胞的核浆之间,以细胞浆和核膜为主,经藤黄酸干预后,Nup88的蛋白和mRNA表达水平明显下降,主要集中于核膜的胞浆面,偶见胞浆中表达.结论 藤黄酸能明显抑制U937白血病细胞的增殖,并诱导其凋亡.而藤黄酸诱导的核孔蛋白Nup88的重新分布以及表达量的下调可能参与了其诱导凋亡作用.     

Aloe‐emodin Induces Apoptosis in Human Liver HL‐7702 Cells through Fas Death Pathway and the Mitochondrial Pathway by Generating Reactive Oxygen Species

Aloe‐emodin (1,8‐dihydroxy‐3‐hydroxymethyl‐anthraquinone) is one of the primary active compounds in total rhubarb anthraquinones isolated from some traditional medicinal plants such as Rheum palmatum L. and Cassia occidentalis, which induce hepatotoxicity in rats. Thus, the aim of this study was to determine the potential cytotoxic effects and the underlying mechanism of aloe‐emodin on human normal liver HL‐7702 cells. The CCK‐8 assays demonstrated that aloe‐emodin decreased the viability of HL‐7702 cells in a dose‐dependent and time‐dependent manner. Aloe‐emodin induced S and G2/M phase cell cycle arrest in HL‐7702 cells. This apoptosis was further investigated by flow cytometry and nuclear morphological changes by DAPI staining, respectively. Moreover, aloe‐emodin provoked the production of intracellular reactive oxygen species and the depolarization of mitochondrial membrane potential (MMP). Further studies by western blot indicated that aloe‐emodin dose‐dependently up‐regulated the levels of Fas, p53, p21, Bax/Bcl‐2 ratio, and cleaved caspase‐3, ‐8, ‐9, and subsequent cleavage of poly(ADP‐ribose)polymerase (PARP). Taken together, these results suggest that aloe‐emodin inhibits cell proliferation of HL‐7702 cells and induces cell cycle arrest and caspase‐dependent apoptosis via both Fas death pathway and the mitochondrial pathway by generating reactive oxygen species, indicating that aloe‐emodin should be taken into account in the risk assessment for human exposure. Copyright © 2017 John Wiley & Sons, Ltd.     

Antiproliferative alkaloids from Crinum zeylanicum

Crinum zeylanicum is used in folk medicine as a rubefacient in rheumatism, a treatment for malaria or as a poison. Complex alkaloid profiles in C. zeylanicum plant organs were revealed by GC‐MS analysis, including several bioactive compounds. Crinine, lycorine, 11‐O‐acetoxyambelline, ambelline, 6‐hydroxybuphanidrine and 6‐ethoxybuphanidrine (an artefact of the isolation procedure) were isolated. Crinine, 6‐hydroxybuphanidrine and 6‐ethoxybuphanidrine showed antiproliferative effects against human tumor cell lines, crinine being the most active (IC₅₀ 14.04 μm against HL‐60/Dox). The latter compound induced apoptosis in a dose‐dependent manner in HL‐60 and MDA‐MB‐231 cell lines. Structure‐activity relationships in the studied molecules indicated that the hydrogenation of the double bond at C1‐C2 leads to a loss of activity, whereas substitutions at C6, C8 and C11 affect their cytotoxicity. Copyright © 2011 John Wiley & Sons, Ltd.     

Activation of AMP‐activated protein kinase on human gastric cancer cells by apoptosis induced by corosolic acid isolated from Weigela subsessilis

Corosolic acid is one of the triterpenoids present in the leaves of Weigela subsessilis. The antidiabetic activity of corosolic acid has been reported previously, but to date, the anticancer effects on gastric cancer have been poorly studied. In this study, corosolic acid showed growth inhibition on SNU‐601 human gastric cancer cells, with an IC₅₀ value of 16.9 ± 2.9 μm . Corosolic acid also triggered the activation of caspase‐3 and poly (ADP‐ribose) polymerase, while it was recovered by Z‐VAD‐FMK. Moreover, the cell growth/apoptosis activities of corosolic acid were regulated by the AMP‐activated protein kinase‐mammalian target of rapamycin (AMPK‐mTOR) signals. These results showed that corosolic acid‐mediated AMPK activation leads to inhibition of mTOR, thus providing a possible mechanism of action of corosolic acid in the inhibition of cancer cell growth and the induction of apoptosis. Copyright © 2010 John Wiley & Sons, Ltd.     

Antitumour effects of ursolic acid isolated from Oldenlandia diffusa

The cytotoxicity-guided fractionation of the MeOH extract of Oldenlandia diffusa (Rubiaceae) led to the isolation of ursolic acid (UA) as an active principle. Ursolic acid demonstrated a significant inhibition of the proliferation of cultured tumour cells, i.e. A549 (human lung), SK-OV-3 (ovary), SK-MEL-2 (skin), XF498 (brain), HCT-15 (colon), SNU-1 (stomach), L1210 (murine leukaemia) and B16-F₀ (murine melanoma). A marked increment of T/C (>200%) was also observed when UA was administered to mice bearing sarcoma-180 cells. The microscopic analyses (phase contrast microscope and TEM) of SNU-1 cell after continuous exposure to UA for 4 and 24 h showed typical morphological changes of the cell due to an apoptotic effect. The nucleosomal DNA of HL60 cells pretreated with UA was cleaved into several oligomeric fragments which was due to a typical apoptotic effect. However, the in vitro cytotoxic effect of UA on tumour cells was decreased in a dose dependent manner by the addition of nicotinamide, a poly-(ADP-ribose) polymerase inhibitor, or aurin tricarboxylic acid (ATA), an endonuclease inhibitor. These results suggested that the cytotoxicity of UA or the apoptotic effect of UA on tumour cells might be related to the activation of the endonucleolytic enzyme and subsequent activation of poly(ADP-ribose) polymerase in tumour cells and these could eventually lead to cell lysis. Copyright © 1998 John Wiley & Sons, Ltd.     

Quercus Suber L. Cork Extracts Induce Apoptosis in Human Myeloid Leukaemia HL‐60 Cells

Quercus suber L. cork contains a diversity of phenolic compounds, mostly low molecular weight phenols. A rising number of reports support with convergent findings that polyphenols evoke pro‐apoptotic events in cancerous cells. However, the literature related to the anti‐cancer bioactivity of Q. suber L. cork extractives (QSE) is still limited. Herein, we aim to describe the antitumor potential displayed by cork extractives obtained by different extraction methods in the human promyelocytic leukaemia cells. In order to quantify the effects of QSE on cancer cells viability, phosphatidylserine exposure, caspase‐3 activity, mitochondrial membrane potential and cell cycle were evaluated. The results indicated that the QSE present a time‐dependent and dose‐dependent cytotoxicity in the human promyelocytic leukaemia cells. Such a noxious effect leads these leukaemia cells to their death through apoptotic processes by altering the mitochondrial outer membrane potential, activating caspase‐3 and externalizing phosphatidylserine. However, cells cycle progression was not affected by the treatments. This study contributes to open a new way to use this natural resource by exploiting its anti‐cancer properties. Moreover, it opens new possibilities of application of cork by‐products, being more efficient in the sector of cork‐based agriculture. Copyright © 2015 John Wiley & Sons, Ltd.     

Cyclooxygenase‐2 inhibitory and antioxidant compounds from the truffle Elaphomyces granulatus

The ethanol extract of fruiting bodies of Elaphomyces granulatus, a truffle‐like fungus, was evaluated for cyclooxygenase‐2 (COX‐2) enzyme inhibitory and antioxidant activities. Inhibition of COX‐2 activity was evaluated in mouse macrophages (RAW 264.7). The extract of E. granulatus caused a 68% inhibition of COX‐2 activity at 50 µg/mL. Bioassay‐guided investigation led to the isolation and identification of two active compounds, syringaldehyde and syringic acid. Syringaldehyde moderately inhibited COX‐2 activity with an IC₅₀ of 3.5 µg/mL, while syringic acid strongly inhibited COX‐2 activity with an IC₅₀ of 0.4 µg/mL. The antioxidant activity of the extract and isolated compounds was evaluated in HL‐60 cells by the DCFH‐DA method. The extract of E. granulatus showed a potent antioxidant effect, with an IC₅₀ of 41 µg/mL. Of the pure compounds, syringic acid displayed a strong antioxidant activity, with an IC₅₀ of 0.7 µg/mL, while syringaldehyde showed no activity in the assay. Copyright © 2008 John Wiley & Sons, Ltd.     

β‐Eudesmol Induces JNK‐Dependent Apoptosis through the Mitochondrial Pathway in HL60 Cells

β‐eudesmol, a natural sesquiterpenol present in a variety of Chinese herbs, is known to inhibit the proliferation of human tumor cells. However, the molecular mechanisms of the effect of β‐eudesmol on human tumor cells are unknown. In the present study, we report the cytotoxic effect of β‐eudesmol on the human leukemia HL60 cells and its molecular mechanisms. The cytotoxic effect of β‐eudesmol on HL60 cells was associated with apoptosis, which was characterized by the presence of DNA fragmentation. β‐eudesmol‐induced apoptosis was accompanied by cleavage of caspase‐3, caspase‐9, and poly (ADP‐ribose) polymerase; downregulation of Bcl‐2 expression; release of cytochrome c from mitochondria; and decrease in mitochondrial membrane potential (MMP). Activation of c‐Jun N‐terminal kinases (JNK) mitogen‐activated protein kinases was observed in β‐eudesmol‐treated HL60 cells, and the inhibitor of JNK blocked the β‐eudesmol‐induced apoptosis, downregulation of Bcl‐2, and the loss of MMP. These data suggest that β‐eudesmol induces apoptosis in HL60 cells via the mitochondrial apoptotic pathway, which is controlled through JNK signaling. Copyright © 2012 John Wiley & Sons, Ltd.     

Pachymic Acid Induces Apoptosis of EJ Bladder Cancer Cells by DR5 Up‐Regulation,ROS Generation,Modulation of Bcl‐2 and IAP Family Members

Pachymic acid (PA) is a lanostane‐type triterpenoid derived from Poria cocos mushroom that possess various biological effects such as anti‐cancer, antiinflammatory and anti‐metastasis effects. In this study, we investigated the anti‐cancer effects of PA in EJ bladder cancer cells. The results showed that PA significantly inhibited proliferation of EJ cells in a dose‐dependent manner. PA induced accumulation of sub‐G1 DNA content (apoptotic cell population), apoptotic bodies and chromatin condensation and DNA fragmentation in EJ cells in a dose‐dependent manner. PA also induces activation of caspase‐3, ‐8 and ‐9, and subsequent cleavage of poly (ADP‐ribose) polymerase, and significantly suppressed the inhibitor of apoptosis protein family proteins in a dose‐dependent manner. Furthermore, PA activates Bid and induced the loss of mitochondrial membrane potential (ΔΨ_m) with up‐regulated pro‐apoptotic proteins (Bax and Bad), down‐regulated anti‐apoptotic proteins (Bcl‐2 and Bcl‐xL) and cytochrome c release. In turn, PA increased the generation of reactive oxygen species (ROS); also, the ROS production was blocked by N‐acetyl‐L‐cysteine. The expressions of TNF‐related apoptosis inducing ligand and death receptor 5 were up‐regulated by PA in a dose‐dependent manner, suggesting extrinsic pathway also involved in PA‐induced apoptosis. This study provides evidence that PA might be useful in the treatment of human bladder cancer. Copyright © 2015 John Wiley & Sons, Ltd.     

Resistance‐modifying Activity in Vinblastine‐resistant Human Breast Cancer Cells by Oligosaccharides Obtained from Mucilage of Chia Seeds (Salvia hispanica)

The multidrug resistance (MDR) phenotype is considered as a major cause of the failure in cancer chemotherapy. The acquisition of MDR is usually mediated by the overexpression of drug efflux pumps of a P‐glycoprotein. The development of compounds that mitigate the MDR phenotype by modulating the activity of these transport proteins is an important yet elusive target. Here, we screened the saponification and enzymatic degradation products from Salvia hispanica seed's mucilage to discover modulating compounds of the acquired resistance to chemotherapeutic in breast cancer cells. Preparative‐scale recycling HPLC was used to purify the hydrolysis degradation products. All compounds were tested in eight different cancer cell lines and Vero cells. All compounds were noncytotoxic at the concentration tested against the drug‐sensitive and multidrug‐resistant cells (IC₅₀ > 29.2 μM). For the all products, a moderate vinblastine‐enhancing activity from 4.55‐fold to 6.82‐fold was observed. That could be significant from a therapeutic perspective. Copyright © 2017 John Wiley & Sons, Ltd.     

Identification of spathulenol in Salvia mirzayanii and the immunomodulatory effects

The methanol extract of Salvia mirzayanii has shown an immunomodulatory effect on peripheral blood lymphocytes. Bioassay‐guided fractionation using a lymphocyte proliferation assay on Salvia mirzayanii was performed in order to purify and identify the active compounds. Fractionation of the methanol extract and purification of the components using normal column chromatography and preparative thin layer chromatography resulted in identification of the bioactive compound, spathulenol, with an immunoinhibitory effect. Identification of this compound was performed by 1D and 2D NMR methods and HRMS. Treatment of activated lymphocytes with a concentrated fraction containing 62% of spathulenol (SP) showed a decrease in the proliferation of lymphocytes with an IC₅₀ of 85.4 ± 11.08 µg/mL. Flow cytometry analysis using annexin V and propidium iodide staining of the stimulated peripheral blood lymphocytes in the presence of SP demonstrated a dose dependent increase in the percentage of apoptotic cells (IC₅₀; 77.2 ± 5.31 µg/mL). No significant increase in caspase 3 activity in a 20 h treatment of stimulated lymphocytes compared with the control was observed. In conclusion, this study identified the possible activity of spathulenol as one of the immunomodulatory compounds present in Salvia mirzayanii. SP showed the capacity to inhibit proliferation in the lymphocytes and to induce apoptosis in these cells possibly through a caspase‐3 independent pathway. Copyright © 2010 John Wiley & Sons, Ltd.     

Potent modulation of P‐glycoprotein activity by naturally occurring phenylbutenoids from Zingiber cassumunar

Five phenylbutenoid derivatives from the rhizomes of Zingiber cassumunar Roxb. (Zingiberaceae) were evaluated for their P‐glycoprotein (P‐gp) inhibitory effects in a P‐gp over‐expressing multidrug resistant (MDR) human breast cancer cell line, MCF‐7/ADR. As a result, a phenylbutenoid dimer, (±)‐trans‐3‐(3,4‐dimethoxyphenyl)‐4‐[(E)‐3,4‐dimethoxystyryl]cyclohex‐1‐ene (1), exhibited highly potent P‐gp inhibitory activity, decreasing the IC₅₀ value of daunomycin (DNM) to 4.31 ± 0.40 µm in the cells (DNM IC₅₀ = 37.1 ± 0.59 µm ). The positive control, verapamil decreased the IC₅₀ value of DNM to 6.94 ± 0.40 µm . Three phenylbutenoid monomers, 2–4 from this plant, also resulted in a significant decrease in the IC₅₀ values of DNM compared with the control. In particular, compound 1 markedly enhanced [³H]‐DNM accumulation and significantly reduced [³H]‐DNM efflux compared with the control, and this effect was more potent than that of verapamil, a well‐known P‐gp inhibitor. These results suggest that compound 1 of Z. cassumunar can be developed as a potent chemo‐sensitizing agent that reverses P‐gp‐mediated MDR in human cancer chemotherapy. Copyright © 2008 John Wiley & Sons, Ltd.     

Cytotoxicity and modes of action of four Cameroonian dietary spices ethno-medically used to treat Cancers: Echinops giganteus, Xylopia aethiopica, Imperata cylindrica and Piper capense

Ethnopharmacological relevance.

Echinops giganteus, Imperata cylindrica, Piper capense and Xylopia aethiopica are four medicinal spices used in Cameroon to treat cancers.

Aim of the study

The above plants previously displayed cytotoxicty against leukemia CCRF-CEM and CEM/ADR5000 cell lines as well as human pancreatic MiaPaCa-2 cells. The present study aims at emphasizing the study of the cytotoxicity and the modes of action of the above plants on a panel of ten cancer cell lines including various sensitive and drug-resistant phenotypes. The study has been extended to the isolation of the bioactive constituents from Echinops giganteus.

Materials and methods

The cytotoxicity of the extracts was determined using a resazurin reduction assay, whereas the caspase-Glo assay was used to detect the activation of caspases 3/7, caspase 8 and caspase 9 in cells treated with the four extracts. Flow cytometry was used for cell cycle analysis and detection of apoptotic cells, analysis of mitochondrial membrane potential (MMP) as well as measurement of reactive oxygen species (ROS).

Results

The four tested extracts inhibited the proliferation of all tested cancer cell lines including sensitive and drug-resistant phenotypes. Collateral sensitivity of cancer cells to the extract of Echinops giganteus was generally better than to doxorubicin. The recorded IC₅₀ ranges were 3.29 µg/mL [against human knockout clones HCT116 (p53^−/−) colon cancer cells] to 14.32 µg/mL (against human liver hepatocellular carcinoma HepG2 cells) for the crude extract from Echinops giganteus, 4.17 µg/mL (against breast cancer cells transduced with control vector MDA-MB231 cells) to 19.45 µg/mL (against MDA-MB-231 BCRP cells) for that of Piper capense, 4.11 µg/mL (against leukemia CCRF-CEM cells) to 30.60 µg/mL (against leukemia HL60AR cells) for Xylopia aethiopica, 3.28 µg/mL [against HCT116 (p53^−/−) cells] to 33.43 µg/mL (against HepG2 cells) for Imperata cylindica and 0.11 µg/mL (against CCRF-CEM cells) to 132.47 µg/mL (against HL60AR cells) for doxorubicin. The four tested extracts induced apoptosis in CCRF-CEM cells via the alteration loss of MMP whilst that of Piper capense also enhanced the production of ROS.

Conclusion

The studied plants are potential cytotoxic drugs that deserve more detailed exploration in the future, to develop novel anticancer drugs against sensitive and otherwise drug-resistant phenotypes.