Plumbagin, isolated from Plumbago zeylanica, induces cell death through apoptosis in human pancreatic cancer cells

Deciphering the binding mechanism of an anti-cancer phytochemical plumbagin with calf thymus DNA using biophysical and in silico techniques

Plumbagin (PLM), a plant derivative, is well known for a wide range of therapeutic effects in humans including anti-cancer, anti-inflammatory, anti-oxidant, and anti-microbial. Cytotoxic and genotoxic potential of this phytochemical has been studied which demands further insight. DNA being a major target for several drugs was taken to study against PLM to understand its effects on the cellular system. UV-Vis spectroscopy has indicated the binding of PLM to ctDNA and dye displacement assays have confirmed the formation of PLM-ctDNA complex. The insignificant changes in circular dichroism spectra suggested that PLM is not affecting the structural makeup of the ctDNA, hence the binding could be peripheral and not intercalating. Further, the relative viscosity and minimal change in melting temperature upon the complex formation supported this finding and confirmed the groove binding of PLM. Molecular docking analysis and simulation studies also show PLM as a minor groove binder to DNA and provide details on the interaction dynamics of PLM-DNA complex. Docking followed by a 100 ns simulation reveals the negative Gibbs free energy change (∆G = -6.6 kcal mol-1), and the formation of a stable complex. The PLM- DNA complex with stable dynamics was further supported by different parameters including RMSD, RMSF, SASA, Rg, and the energy profile of interaction. This study provides an insight into the cytotoxic and genotoxic mechanism of PLM which can be a crucial step forward to exploit its therapeutic potential against several diseases including cancer.

Future Prospective of Radiopharmaceuticals from Natural Compounds Using Iodine Radioisotopes as Theranostic Agents

Natural compounds provide precursors with various pharmacological activities and play an important role in discovering new chemical entities, including radiopharmaceuticals. In the development of new radiopharmaceuticals, iodine radioisotopes are widely used and interact with complex compounds including natural products. However, the development of radiopharmaceuticals from natural compounds with iodine radioisotopes has not been widely explored. This review summarizes the development of radiopharmaceuticals from natural compounds using iodine radioisotopes in the last 10 years, as well as discusses the challenges and strategies to improve future discovery of radiopharmaceuticals from natural resources. Literature research was conducted via PubMed, from which 32 research articles related to the development of natural compounds labeled with iodine radioisotopes were reported. From the literature, the challenges in developing radiopharmaceuticals from natural compounds were the purity and biodistribution. Despite the challenges, the development of radiopharmaceuticals from natural compounds is a golden opportunity for nuclear medicine advancement.

Traditional and Phytochemical Bases of Herbs, Shrubs, Climbers, and Trees from Ethiopia for Their Anticancer Response

Ethiopia is one of Africa's six plant-rich countries, with around 60% of the plants being indigenous and most of them having medicinal properties. 80% of people in the country use these plants as a primary health care system to tackle different diseases, including cancer. This review is aimed at summarizing the evidence gained from diverse MPs in Ethiopia that have been used ethnobotanically and ethnopharmacologically for treatment of cancer. The primary data sources were Google Scholar, Web of Science, Science Direct, Scopus, PubMed, and other electronic scientific databases. This literature review showed that there are around 200 MPs used as anticancer. Seventy-four herbs, 39 trees, 77 shrubs, and 17 weed/climbers belonging to 56 families have been identified for their ethnobotanical anticancer potential, and 31 species were recognized for their pharmaceutically anticancer activities. The reviewed data also indicated that many Ethiopian MPs had been used to treat breast, lung, blood, and skin cancers and other tumors. Besides, the collected data showed that the leaves (36.76%), roots (27.2%), bark (12.5%), stem (5.1%), and fruit (7.35%) of plants are commonly used for the preparation of anticancer remedies. Among the reported plant species, Euphorbiaceae (10.71%), Acanthaceae (7.14%), and Asteraceae (7.1%) are the most prominent plant families being used to treat cancer ethnobotanically. Phytochemicals such as flavonoids (like xanthone, indirubin, flavopiridol, and silybin), alkaloids (like taxol, vincristine, evodiamine, and berberine), and physalin B, D, and F steroids exhibited anticancer activity on various cancer cell lines. The crude extracts of Aerva javanica, Vernonia leopoldi, Withania somnifera, Kniphofia foliosa, and Catharanthus roseus were powerful anticancer agents with an IC₅₀ value below 10 μg/mL. Although several Ethiopian plants possess anticancer potential, only a limited number of plants are scientifically studied. Therefore, more scientific studies on anticancer MPs should be carried out; it may lead to discovering and isolating cost-effective and safe anticancer drugs.

Herbals and Plants in the Treatment of Pancreatic Cancer: A Systematic Review of Experimental and Clinical Studies

Background: Pancreatic cancer represents the most lethal malignancy among all digestive cancers. Despite the therapeutic advances achieved during recent years, the prognosis of this neoplasm remains disappointing. An enormous amount of experimental (mainly) and clinical research has recently emerged referring to the effectiveness of various plants administered either alone or in combination with chemotherapeutic agents. Apart from Asian countries, the use of these plants and herbals in the treatment of digestive cancer is also increasing in a number of Western countries as well. The aim of this study is to review the available literature regarding the efficacy of plants and herbals in pancreatic cancer. Methods: The authors have reviewed all the experimental and clinical studies published in Medline and Embase, up to June 2021. Results: More than 100 plants and herbals were thoroughly investigated. Favorable effects concerning the inhibition of cancer cell lines in the experimental studies and a favorable clinical outcome after combining various plants with established chemotherapeutic agents were observed. These herbals and plants exerted their activity against pancreatic cancer via a number of mechanisms. The number and severity of side-effects are generally of a mild degree. Conclusion: A quite high number of clinical and experimental studies confirmed the beneficial effect of many plants and herbals in pancreatic cancer. More large, double-blind clinical studies assessing these natural products, either alone or in combination with chemotherapeutic agents should be conducted.

Phyto-targeting the CEMIP Expression as a Strategy to Prevent Pancreatic Cancer Metastasis

INTRODUCTION

Metastasis of primary pancreatic cancer (PC) to adjacent or distant organs is responsible for the poor survival rate of affected individuals. Chemotherapy, radiotherapy, and immunotherapy are currently being prescribed to treat PC in addition to surgical resection. Surgical resection is the preferred treatment for PC that leads to 20% of 5-year survival, but only less than 20% of patients are eligible for surgical resection because of the poor prognosis. To improve the prognosis and clinical outcome, early diagnostic markers need to be identified, and targeting them would be of immense benefit to increase the efficiency of the treatment. Cell migration-inducing hyaluronan-binding protein (CEMIP) is identified as an important risk factor for the metastasis of various cancers, including PC. Emerging studies have pointed out the crucial role of CEMIP in the regulation of various signaling mechanisms, leading to enhanced migration and metastasis of PC.

METHODS

The published findings on PC metastasis, phytoconstituents, and CEMIP were retrieved from Pubmed, ScienceDirect, and Cochrane Library. Computational tools, such as gene expression profiling interactive analysis (GEPIA) and Kaplan-Meier (KM) plotter, were used to study the relationship between CEMIP expression and survival of PC individuals.

RESULTS

Gene expression analysis using the GEPIA database identified a stupendous increase in the CEMIP transcript in PC compared to adjacent normal tissues. KM plotter analysis revealed the impact of CEMIP on the overall survival (OS) and disease-free survival (DFS) among PC patients. Subsequently, several risk factors associated with PC development were screened, and their ability to regulate CEMIP gene expression was analyzed using computational tools.

CONCLUSION

The current review is focused on gathering information regarding the regulatory role of phytocomponents in PC migration and exploring their possible impact on the CEMIP expression.

Redox ticklers and beyond: Naphthoquinone repository in the spotlight against inflammation and associated maladies

Cellular redox status has been considered as a focal point for the pathogenesis of multiple disorders. High and persistent levels of free radicals kick off inflammation and associated disorders. Though oxidative stress at high levels is harmful but at low levels it has been shown to exert cytoprotective effects. Therefore, cytoprotection by perturbation in cellular redox balance is a leading strategy for therapeutic interventions. Prooxidants are potent redox modifiers that generate mild oxidative stress leading to a spectrum of bioactivities. Naphthoquinones are a group of highly reactive organic chemical species that interact with biological systems owing to their prooxidants nature. Owing to the ability of naphthoquinones and its derivatives to perturb redox balance in a cell and modulate redox signaling, they have been in epicenter of drug development for plausible utilization in multiple clinical settings. The present review highlights the potential of 1,4-naphthoquinone and its natural derivatives (plumbagin, juglone, lawsone, menadione, lapachol and β-lapachone) as redox modifiers with anti-inflammatory, anti-cancer, anti-diabetic and anti-microbial activities for implication in therapeutic settings.

Light emitting diodes optimisation for secondary metabolites production by Droseraceae plants

The most abundant active compound in Droseraceae is plumbagin, a naphthoquinone widely used for medical purposes due to its antimicrobial, antitussive, antimalarial and anticancer properties. In this work, we created a light-emitting diode (LED) based culture illumination setup as an alternative to fluorescent lamps traditionally used as a light source in plant in vitro cultures. The plants of Drosera binata and Drosera peltata cultured under LED illumination grew equally well and produced similar amounts of biologically active compounds as plants grown under fluorescent lamps. The plants were cultured on two media differing in mineral composition, sucrose content and pH. Secondary metabolites were extracted with ethanol from the plants after harvesting. The extracts were subjected to HPLC and microbiological analyses. We observed differences in morphology and secondary metabolism between plants of the same species grown on different media. However, we did not note significant changes in secondary metabolite yield under assessed lighting conditions. We propose LEDs as a more efficient, eco-friendly and economically reasonable source of light for big scale in vitro production of plumbagin in Drosera species than fluorescent lamps.

Plumbagin: A Potential Anti-cancer Compound

Cancer is a deadly disease, which has significantly increased in both developed and developing nations. Treatment of cancer utilizing radiotherapy or chemotherapy actuates a few issues which incorporate spewing, sickness, unpalatable reactions, and so forth. In this specific situation, an alternative drug source, which can effectively treat cancer is of prime importance. Products that are obtained from plant sources are utilized for the treatment of various diseases due to their non-harmful nature. Medicinal plants contain different bioactive compounds, which possess an important role in the prevention of different diseases such as cancer. Plumbagin is a bioactive compound, which is mainly present in Plumbaginaceae family and has been explored for its anticancer activity. Plumbagin basically inactivates the Akt/NF-kB, MMP-9 and VEGF pathways that are essential for cancer cell development. Therefore, it is important to review the role of plumbagin in different cancer cells in order to find an alternative drug to overcome this disease. The present review provides a summary of anticancer activity of plumbagin in various cancers and its mode of action.

Ethiopian Medicinal Plants Traditionally Used for the Treatment of Cancer, Part 2: A Review on Cytotoxic, Antiproliferative, and Antitumor Phytochemicals, and Future Perspective

This review provides an overview on the active phytochemical constituents of medicinal plants that are traditionally used to manage cancer in Ethiopia. A total of 119 articles published between 1968 and 2020 have been reviewed, using scientific search engines such as ScienceDirect, PubMed, and Google Scholar. Twenty-seven medicinal plant species that belong to eighteen families are documented along with their botanical sources, potential active constituents, and in vitro and in vivo activities against various cancer cells. The review is compiled and discusses the potential anticancer, antiproliferative, and cytotoxic agents based on the types of secondary metabolites, such as terpenoids, phenolic compounds, alkaloids, steroids, and lignans. Among the anticancer secondary metabolites reported in this review, only few have been isolated from plants that are originated and collected in Ethiopia, and the majority of compounds are reported from plants belonging to different areas of the world. Thus, based on the available bioactivity reports, extensive and more elaborate ethnopharmacology-based bioassay-guided studies have to be conducted on selected traditionally claimed Ethiopian anticancer plants, which inherited from a unique and diverse landscape, with the aim of opening a way forward to conduct anticancer drug discovery program.

Emerging role of plumbagin: Cytotoxic potential and pharmaceutical relevance towards cancer therapy

Plumbagin is a naphthoquinone derived yellow crystalline phytochemical. Plumbagin has a wide range of biological effects including cytotoxicity against cancer cells both in vitro and in vivo. Due to the pleiotropic nature of plumbagin, it shows the anticancer effect by targeting several molecular mechanisms including apoptosis and autophagic pathways, cell cycle arrest, anti-angiogenic pathways, anti-invasion and anti-metastasis pathways. Among many signaling pathways the key regulatory genes regulated by plumbagin are NF-kβ, STAT3, and AKT, etc. Plumbagin is also a potent inducer of ROS, suppressor of cellular glutathione, and causes DNA strand break by oxidative DNA base damages. In vivo studies suggested that plumbagin significantly reduces the tumor weight and volume in dose-dependent manner without any side effects in tested model organisms. Another exciting aspect of plumbagin is the ability to re-sensitize the chemo and radioresistant cancer cells when used in combination or alone. Nano encapsulation of plumbagin overcomes the poor water solubility and bioavailability obstacles, enhancing the pharmaceutical relevance with better therapeutic efficacy. Moreover, plumbagin can be introduced as a future phytotherapeutic anticancer drug after fully satisfied preclinical and clinical trials.

Molecular insight into the therapeutic potential of phytoconstituents targeting protein conformation and their expression

BACKGROUND

Native protein conformation is essential for the functional activity of the proteins and enzymes. Defects in conformation or alterations in expression of the proteins have been reported in various diseases.

PURPOSE

The aim of this study is to review the molecular insight into the therapeutic potential of phytoconstituents targeting protein conformations or expressions.

METHODS

Published literatures were searched in PubMed, Scopus, Web of Science; Article published till Dec 2017 were extracted. The literature was assessed from the Central University of Rajasthan, India. Present study evaluate article based on the role of active plant constituents on the conformation and expression of the different proteins.

RESULTS

Plant components play their role either at the molecular level or cellular level and exhibit antibacterial, antiviral, anti-neurodegenerative and other activities. Plant active compounds isolated from different plants may either stabilize or destabilize the conformation of proteins or alter expression level of the protein involved in these diseases, therefore, can play a significant role in preventing diseases caused by the alteration in these proteins.

CONCLUSION

In the present article, we have reviewed the molecular mechanism of plant active compounds, their target proteins, methods of extraction and identification, and their biological significances. Therefore, a proper understanding of the effect of these herbal molecules on the concerned proteins may help to develop new herbal-based therapeutics for various diseases.

Chemosuppressive effect of plumbagin on human non-small lung cancer cell xenotransplanted zebrafish

BACKGROUND

Plumbagin (5-hydroxy-2-methyl-1,4-napthoquinone) derived from Plumbago species is a potential anti-tumour agent. Plumbagin has been tested for anti-cancer activity in vitro and in vivo using mice model.

AIM

To study the tumour suppressing efficacy of plumbagin using zebrafish model.

MATERIALS AND METHODS

Human Non-small lung cancer cell line were cultured in vitro and transplanted in to zebrafish. The development of tumour was confirmed by performing histology. The tumour was then allowed to progress in vivo and the fishes were administered with plumbagin orally for three continuous days. The tumour suppression capacity was monitored subsequently using transcriptosome analysis.

STATISTICAL METHODS

The pixel integrated density obtained was converted into relative gene expression using IBM SPSS.

RESULTS

The administration of plumbagin had an ability to suppress tumour and the size of the tumour were relatively lesser when compared with the control sample; it has also increased p53 gene expression.

CONCLUSION

The study helps to conclude that plumbagin is an effective anti-tumour agent against human cancer cells based on the study in vivo in zebrafish.

The attenuating effects of plumbagin on pro-inflammatory cytokine expression in LPS-activated BV-2 microglial cells

Activated microglial cells produce the pro-inflammatory mediators such as nitric oxide (NO) and cytokines. The excessive release of these mediators can lead to neurodegenerative diseases, such as Alzheimer's disease (AD) and Parkinson's disease (PD). Inhibition of the release of these pro-inflammatory molecules may prevent or halt the progression of these diseases. Plumbagin (PL), a naphthoquinone compound in the roots of the traditional medicinal plant Plumbago zeylanica L., showed anti-inflammatory effects on macrophages. However, PL effects on activated microglia remain unknown. In the present study, PL has been examined for its anti-inflammatory effect on LPS - activated microglial BV-2 cells. In this study, NO and iNOS expression were investigated in BV-2 microglial cells in the presence of PL or the selective iNOS inhibitor L-N6-(1-iminoethyl) lysine (L-NIL). The results obtained indicate that PL was >30-fold potent than L-NIL in inhibiting NO production with an IC₅₀ of 0.39μM. Our immunofluorescence study confirmed the ability of PL to significantly inhibit iNOS expression in the activated microglia. Furthermore, the extracellular microglial pro-inflammatory cytokine expression in the presence of 2μM of PL was detected, quantified, and validated using cytokine antibody protein arrays and quantitative ELISA. The results obtained showed that PL significantly downregulated the expression of many cytokines including IL-1α, G-CSF, IL-12 p40/p70, MCP-5, MCP-1, and IL-6. In conclusion, PL potency in attenuating multiple pro-inflammatory agents indicates its potential to be used for neurodegenerative diseases.

Neuroprotection by plumbagin involves BDNF-TrkB-PI3K/Akt and ERK1/2/JNK pathways in isoflurane-induced neonatal rats

OBJECTIVES

This study was designed to assess the effects of plumbagin on isoflurane-induced neurotoxicity.

METHODS

Neonatal Sprague Dawley rat pups were treated with plumbagin (50, 100 or 150 mg/kg body weight, orally) from postnatal day 2. The pups on postnatal day 7 were subjected to isoflurane (0.75%) exposure for 6 h. Neuronal apoptosis in the hippocampal tissues was detected by TUNEL assay and FluroJade B staining following isoflurane exposure. Protein expressions were analysed by immunoblotting. RT-PCR was performed to assess mRNA levels of brain-derived neurotrophic factor (BDNF) and TrkB.

KEY FINDINGS

We observed reduced apoptosis in hippocampal CA1, CA3 and dentate gyrus regions along with severely reduced pro-apoptotic factors (Bad, Bax and cleaved caspase-3) expression and raised levels of Bcl-2, Bcl-xL, survivin, xIAP and cIAPs (cell survival proteins) in plumbagin supplemented rats. Decrease in the levels of JNK, phospho-JNK, c-Jun and phospho-c-Jun with enhanced ERK1/2 levels was observed on plumbagin pretreatment. Down-regulated PI3K/Akt signalling following isoflurane was activated by plumbagin as evidenced by raised PI3K/Akt pathway proteins - mTORc1, Akt, phospho-Akt, GSK-3β, phospho-GSK-3β, PTEN and NF-κBp65 in the hippocampal tissues as detected by Western blotting. The mRNA levels were enhanced on plumbagin supplementation.

CONCLUSIONS

Plumbagin exerted its neuroprotective effects by effectively suppressing isoflurane-induced neuronal apoptosis via regulating BDNF-TrkB-PI3/Akt and ERK/JNK signalling.

Anticancer Properties and Pharmaceutical Applications of Plumbagin: A Review

It has been shown that plumbagin, a bioactive naphthoquinone isolated from three major plant families viz. Plumbaginaceae, Ebenceae and Droseraceae, definitively exhibits anticancer potential in diverse cancer cells both in vitro and in vivo. Plumbagin shows antineoplastic effects via multi-channel molecular mechanisms, including the induction of apoptosis and autophagy, the disruption of the cell cycle, the inhibition of invasion and metastasis, and anti-angiogenesis. Plumbagin inhibits the growth of cancer cells mainly through the modulation of the signals of PI3K/Akt/mTOR, AMPK, Ras, and so on. The pharmaceutical applications of plumbagin combined with nanocarriers to achieve better therapeutic efficiency are discussed in this review Among them, liposomes, nanoparticles, microspheres, micelles, and nisosomes are used in cancer treatment. The anticancer study of plumbagin in vivo is also summarized in this review. On the whole, we aim to review the research progress of plumbagin both in pharmacological and pharmaceutical filed, which may provide some reference for further research of plumbagin.

Potential mode of action of a novel plumbagin as a mosquito repellent against the malarial vector Anopheles stephensi, (Culicidae: Diptera)

Plumbagin was isolated and characterized from the roots of Plumbago zeylanica using chromatography: TLC, Column chromatogram, HPLC, FTIR and ¹H NMR. The isolated pure compounds were assayed for potency as inhibitors of: acetylcholine esterase (AchE), glutathione S-transferases (GST), superoxide dismutase (SOD), cytochrome P450 and α, β-esterase, and for repellency with Anopheles stephensi at four different concentrations (25, 50, 75 and 100ppm). The enzyme assay against the pure compound reveals that the level of esterase and SOD was decreased significantly in contrast the level of GST and cytochrome P450 was increased significantly. Our results suggests that novel Plumbagin has significantly alters the level of enzyme comparable to the control. Evaluations resulted in Plumbagin producing maximum repellency scores against An. stephensi mosquitoes in dose dependent manner with highest repellence was observed in the 100ppm. Histological examination showed that the midgut, hindgut and muscles are the most affected tissues. These tissues affected with major changes including separation and collapse of epithelial layer and cellular vacuolization. The results support the utility of plant compound Plumbagin for vector control as an alternative to synthetic insecticides, however, more vigorous field trials are needed to determine viability under natural conditions.

Comparative toxicity profiles of Plumbago zeylanica L. root petroleum ether, acetone and hydroalcoholic extracts in Wistar rats

Introduction:

The root of Plumbago zeylanica Linn. is used in traditional medicine for the treatment of chronic inflammatory diseases and various disorders. The toxicity of this plant has not yet been extensively evaluated.

Aim:

To evaluate and compare the toxicity of P. zeylanica root petroleum ether (PZPE), acetone (PZAC), and the hydroalcoholic (PZHY) extracts.

Materials and Methods:

The acute and sub-acute toxicities of extracts were evaluated according to OECD guidelines 425 and 407, respectively in female rats.

Results:

PZPE was more toxic than PZAC and PZHA, based on LD50 values of 93.45, 928.4, and 928.4 mg/kg, respectively. This potency difference directly correlates with the plumbagin content of extracts. With regard to sub-acute toxicity, a significant increase in organ weights (liver, adrenal glands, and/or heart) was observed in PZPE and PZAC treated groups. All extracts produced a significant increase in serum aspartate aminotransferase and urea, and PZAC produced a significant increase in serum creatinine as compared to control. A decrease in hematocrit was observed in the highest dose PZPE group, and a decrease in leukocytes was observed in all PZAC groups. Hepatic and renal changes were observed in all extract treated groups.

Conclusion:

The findings of our study, thus demonstrate that liver and kidney are the primary organs being adversely affected following sub-acute administration of P. zeylanica root extract in rats.

Inhibition of ANO1/TMEM16A Chloride Channel by Idebenone and Its Cytotoxicity to Cancer Cell Lines

The expression levels of anoctamin 1 (ANO1, TMEM16A), a calcium-activated chloride channel (CaCC), are significantly increased in several tumors, and inhibition of ANO1 is known to reduce cell proliferation and migration. Here, we performed cell-based screening of a collection of natural products and drug-like compounds to identify inhibitors of ANO1. As a result of the screening, idebenone, miconazole and plumbagin were identified as novel ANO1 inhibitors. Electrophysiological studies showed that idebenone, a synthetic analog of coenzyme Q10, completely blocked ANO1 activity in FRT cells expressing ANO1 without any effect on intracellular calcium signaling and CFTR, a cAMP-regulated chloride channel. The CaCC activities in PC-3 and CFPAC-1 cells expressing abundant endogenous ANO1 were strongly blocked by idebenone. Idebenone inhibited cell proliferation and induced apoptosis in PC-3 and CFPAC-1 cells, but not in A549 cells, which do not express ANO1. These data suggest that idebenone, a novel ANO1 inhibitor, has potential for use in cancer therapy.

Plumbagin suppresses tumor cell growth in oral squamous cell carcinoma cell lines

OBJECTIVES

Plumbagin (PL), a naturally occurring quinoid, exerts antitumoral effects in diverse types of cancer cells. However, the effect of PL on tumor cell proliferation in oral squamous cell carcinoma (OSCC) remains poorly understood. In this study, we assessed the efficacy of PL, in human OSCC cells.

METHODS

The effect of PL on the cell growth and apoptosis of OSCC cell lines was evaluated using MTT and Annexin V assays, respectively. The effect of PL on mitochondrial membrane potential loss and reactive oxygen species (ROS) generation was evaluated using flow cytometry analysis.

RESULTS

MTT assay showed that PL dose-dependently suppressed OSCC cell growth, with IC50 values ranging from 3.87 to 14.6 μM. Flow cytometry analysis revealed that PL treatment resulted in a significant decrease in mitochondrial membrane potential and an increase in the number of apoptotic cells. Notably, ROS generation was significantly elevated after PL treatment. Furthermore, a ROS scavenger, N-acetylcysteine (NAC), clearly suppressed the decrease in mitochondrial membrane potential, increase of caspase-3/7 activity, and apoptosis after PL treatment.

CONCLUSION

This study provides the considerable evidence of the tumor-suppressive effect of PL, thereby highlighting its therapeutic potential for OSCC treatment.

Plumbagin Inhibits Prostate Carcinogenesis in Intact and Castrated PTEN Knockout Mice via Targeting PKCε, Stat3, and Epithelial-to-Mesenchymal Transition Markers

Prostate cancer continues to remain the most common cancer and the second leading cause of cancer-related deaths in American males. The Pten deletions and/or mutations are frequently observed in both primary prostate cancers and metastatic prostate tissue samples. Pten deletion in prostate epithelium in mice results in prostatic intraepithelial neoplasia (PIN), followed by progression to invasive adenocarcinoma. The Pten conditional knockout mice [(Pten-loxp/loxp:PB-Cre4(+)) (Pten-KO)] provide a unique preclinical model to evaluate agents for efficacy for both the prevention and treatment of prostate cancer. We present here for the first time that dietary plumbagin, a medicinal plant-derived naphthoquinone (200 or 500 ppm) inhibits tumor development in intact as well as castrated Pten-KO mice. Plumbagin has shown no signs of toxicity at either of these doses. Plumbagin treatment resulted in a decrease expression of PKCε, AKT, Stat3, and COX2 compared with the control mice. Plumbagin treatment also inhibited the expression of vimentin and slug, the markers of epithelial-to-mesenchymal transition (EMT) in prostate tumors. In summary, the results indicate that dietary plumbagin inhibits growth of both primary and castration-resistant prostate cancer (CRPC) in Pten-KO mice, possibly via inhibition of PKCε, Stat3, AKT, and EMT markers (vimentin and slug), which are linked to the induction and progression of prostate cancer.

Plant-derived anticancer agents: a promising treatment for bone metastasis

Bone metastasis is a very frequent complication of advanced cancer, and it remains an incurable disease. Current therapies that have been approved for the treatment of bone metastases delay the occurrence of skeletal-related events and can extend the patient's lifespan by a few years. However, they will not cure or cause the regression of established bone metastases, and new side effects are emerging after prolonged treatment. Thus, new therapies are severely needed. There are compelling evidences from in vitro and in vivo preclinical studies that support the use of compounds derived from plants to treat several forms of cancers including bone metastasis. More than 25% of the drugs used during the past 20 years were directly derived from plants, whereas another 25% are chemically altered natural products. Still, only 5-15% of the ∼250 000 higher plants have ever been investigated for bioactive compounds. There is a growing interest for the study of anticancer drugs with relatively low side effects that target specific key signaling pathways that control the establishment and progression of the cancer metastasis. Therefore, further studies are needed to identify new natural compounds with high efficiency in cancer prevention and treatment. Extensive reviews about plant-derived agents and their use in cancer have been published, but none when it comes to the treatment of bone metastases. Only a few of these compounds have been evaluated for the treatment of bone metastasis; here we describe some of the most prominent ones that are having the potential to reach the clinic soon.

A small library of synthetic di-substituted 1, 4-naphthoquinones induces ROS-mediated cell death in murine fibroblasts

Synthesis of compound libraries and their concurrent assessment as selective reagents for probing and modulating biological function continues to be an active area of chemical biology. Microwave-assisted solid-phase Dötz benzannulation reactions have been used to inexpensively synthesize 2, 3-disubstituted-1, 4-naphthoquinone derivatives. Herein, we report the biological testing of a small library of such compounds using a murine fibroblast cell line (L929). Assessment of cellular viability identified three categories of cytotoxic compounds: no toxicity, low/intermediate toxicity and high toxicity. Increased levels of Annexin-V-positive staining and of caspase 3 activity confirmed that low, intermediate, and highly toxic compounds promote cell death. The compounds varied in their ability to induce mitochondrial depolarization and formation of reactive oxygen species (ROS). Both cytotoxic and non-cytotoxic compounds triggered mitochondrial depolarization, while one highly cytotoxic compound did not. In addition, all cytotoxic compounds promoted increased intracellular ROS but the cells were only partially protected from compound-induced apoptosis when in the presence of superoxide dismutase, catalase, or ascorbic acid suggesting utilization of additional pro-death mechanisms. In summary, nine of twelve (75%) 1, 4-naphthoquinone synthetic compounds were cytotoxic. Although the mitochondria did not appear to be a central target for induction of cell death, all of the cytotoxic compounds induced ROS formation. Thus, the data demonstrate that the synthesis regime effectively created cytotoxic compounds highlighting the potential use of the regime and its products for the identification of biologically relevant reagents.

Ethnopharmacological survey of medicinal plants used by traditional health practitioners in Thanchi, Bandarban Hill Tracts, Bangladesh

ETHNOPHARMACOLOGICAL RELEVANCE

There is very limited information regarding plants used by traditional healers in Bandarban Hill Tracts (BHT), Bangladesh for treating general as well as complex ailments. Current study provides significant ethnopharmacological information, both qualitative and quantitative on medical plants in BHT. Aim of the study This study aimed to collect, analyze and evaluate the rich ethnopharmacologic knowledge on medicinal plants in Thanchi, BHT and attempted to identify the important species used in traditional medicine. Further analysis was done by comparison of the traditional medicinal use of the plants with the available scientific literature data.

MATERIALS AND METHODS

The field survey was carried out in a period of several years in Thanchi upazilla of Bandarban districts, Bangladesh. A total of 53 Traditional Health Practitioners (THPs) were interviewed through open-ended and semi structured questionnaire. The collected data were analyzed qualitatively and quantitatively. This ethnomedicinal knowledge was compared against the available scientific literature for reports of related uses and studies of phytochemical compounds responsible for respective ailments.

RESULTS

A total of 84 species of plants, mostly herbs, belonging to 42 families were identified for the treatment of 70 types of ailments. These ailments were categorized into 16 categories. Leaves were the most frequently used plant parts and juice is the mode of preparation of major portions of the plant species. The most common mode of administration was oral ingestion and topical application. Informant consensus factor (Fic) values of the present study reflected the high agreement in the use of plants in the treatment of digestive system and respiratory system disorders among the informants. Diseases of the digestive system had highest use-reports and 3 species of plants, namely Centella asiatica (L.) Urban. (dysentery), Justicia gendarussa L. (asthma) and Ocimum tenuiflorum L. (coughing) had the highest fidelity level (FL) of 100%. Clerodendrum viscosum Vent., Achyranthes aspera L and Justicia gendarussa L. showed the highest relative importance (RI) value of 1.86. According to use value (UV) the most important species were Ocimum tenuiflorum L. (2.24) and Achyranthes aspera L. (2.15).

CONCLUSION

Priority should be given for further phytochemical investigation to plants that scored highest FL, Fic, UV or RI values, as such values could be considered as good indicator of prospective plants for discovering new drugs. Since knowledge regarding traditional medicine being vulnerable day by day so traditional medicine in school curricula should be incorporated so that younger people could appreciate its usefulness. Also counseling of THPs and gardening of medicinal plants should be taken into consideration immediately in order to smooth continuance and extension of traditional medical knowledge and practice for ensuring safe and effective therapy.

Use of herbal medicines and natural products: an alternative approach to overcoming the apoptotic resistance of pancreatic cancer

Pancreatic cancer has a poor prognosis with a 5-year survival rate of <5%. It does not respond well to either chemotherapy or radiotherapy, due partly to apoptotic resistance (AR) of the cancer cells. AR has been attributed to certain genetic abnormalities or defects in apoptotic signaling pathways. In pancreatic cancer, significant mutations of K-ras and p53, constitutive activation of NFκB, over-expression of heat shock proteins (Hsp90, Hsp70), histone deacetylase (HDACs) and the activities of other proteins (COX-2, Nrf2 and bcl-2 family members) are closely linked with resistance to apoptosis and invasion. AR has also been associated with aberrant signaling of MAPK, PI3K-AKT, JAK/STAT, SHH, Notch, and Wnt/β-catenin pathways. Strategies targeting these signaling molecules and pathways provide an alternative for overcoming AR in pancreatic cancer. The use of herbal medicines or natural products (HM/NPs) alone or in combination with conventional anti-cancer agents has been shown to produce beneficial effects through actions upon multiple molecular pathways involved in AR. The current standard first-line chemotherapeutic agents for pancreatic cancer are gemcitabine (Gem) or Gem-containing combinations; however, the efficacy is dissatisfied and this limitation is largely attributed to AR. Meanwhile, emerging data have pointed to a combination of HM/NPs that may augment the sensitivity of pancreatic cancer cells to Gem. Greater understanding of how these compounds affect the molecular mechanisms of apoptosis may propel development of HM/NPs as anti-cancer agents and/or adjuvant therapies forward. In this review, we give a critical appraisal of the use of HM/NPs alone and in combination with anti-cancer drugs. We also discuss the potential regulatory mechanisms whereby AR is involved in these protective pathways.

Anticancer compound plumbagin and its molecular targets: a structural insight into the inhibitory mechanisms using computational approaches

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone) is a naphthoquinone derivative from the roots of plant Plumbago zeylanica and belongs to one of the largest and diverse groups of plant metabolites. The anticancer and antiproliferative activities of plumbagin have been observed in animal models as well as in cell cultures. Plumbagin exerts inhibitory effects on multiple cancer-signaling proteins, however, the binding mode and the molecular interactions have not yet been elucidated for most of these protein targets. The present study is the first attempt to provide structural insights into the binding mode of plumbagin to five cancer signaling proteins viz. PI3Kγ, AKT1/PKBα, Bcl-2, NF-κB, and Stat3 using molecular docking and (un)binding simulation analysis. We validated plumbagin docking to these targets with previously known important residues. The study also identified and characterized various novel interacting residues of these targets which mediate the binding of plumbagin. Moreover, the exact modes of inhibition when multiple mode of inhibition existed was also shown. Results indicated that the engaging of these important interacting residues in plumbagin binding leads to inhibition of these cancer-signaling proteins which are key players in the pathogenesis of cancer and thereby ceases the progression of the disease.

Plumbagin induces the apoptosis of human tongue carcinoma cells through the mitochondria-mediated pathway

BACKGROUND

Plumbagin, a quinonoid constituent isolated from the root of Plumbago zeylanica L., has been proven to possess anti-tumor activity both in vitro and in vivo. However, its anti-tumor properties for human tongue carcinoma have not been reported. This study aimed to investigate the inhibitory effect and the underlying mechanism of plumbagin on the growth of human tongue carcinoma cells.

MATERIAL AND METHODS

Cell proliferation ability was detected by EdU incorporation assay and colony formation assay. Cell-cycle distribution was determined by flow cytometric analysis using propidium iodide (PI) staining. Cellular apoptosis was then evaluated by flow cytometry and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. Western blotting was applied to assay the expression of Bax and Bcl-2.

RESULTS

Plumbagin inhibited the growth and proliferation of Tca8113 cells in vitro in a concentration- and time-dependent manner. The cell cycles of plumbagin-treated Tca8113 cells were arrested at the G2/M phase. Cells treated with plumbagin presented the characteristic morphological changes of apoptosis. The ratio of Bax/Bcl-2 was raised by plumbagin in a concentration-dependent manner.

CONCLUSIONS

These results indicate that plumbagin induces the apoptosis of Tca8113 cells through mitochondria-mediated pathway.

Interplay between autophagy and apoptosis in pancreatic tumors in response to gemcitabine

Pancreatic cancer is an aggressive disease. Its incidence has increased over the last two decades. It is currently the fourth cause of death among cancers in the western world. Unfortunately, systemic chemotherapy still relies on just a few drugs which until now have produced unsatisfactory results. Gemcitabine (2'-2'-difluorodeoxycytidine) is currently the standard chemotherapy treatment at all stages of pancreatic adenocarcinoma. Survival benefit and clinical impact however remain moderate due to a high degree of intrinsic and acquired resistance. Autophagy plays an important role in cell death decision but can also protect cells from various apoptotic stimuli. We investigated the function of autophagy in pancreatic carcinoma cells, which are frequently insensitive to standard chemotherapeutic agents. Here, we demonstrate that autophagy is one of the mechanisms responsible for the refractory response of pancreatic tumors to gemcitabine. We present evidence in vitro and in vivo that proves autophagy plays a protective role in pancreatic ductal carcinoma cells, preventing them from entering the apoptotic pathway after stimulus with gemcitabine, thus contributing to treatment resistance. A better understanding of the role in the process may help in the discovery of new strategies to overcome tumor drug resistance in this aggressive disease.

The synergistic effects of traditional Chinese herbs and radiotherapy for cancer treatment

Traditional Chinese medicine (TCM) has been demonstrated to have potent cytotoxic activity against certain malignant tumors. Ionizing radiation (IR) is one of the most effective methods used in the clinical treatment of cancer. The drawback of a single formula is that it limits the treatment efficacy for cancer, while comprehensive strategies require additional theoretical support. However, a combination of different antitumor treatment modalities is advantageous in restricting the non-specific toxicity often observed with an extremely high dose of a single regimen. The induction of apoptotic cell death is a significant process in tumor cells following radiotherapy or chemotherapy, and resistance to these treatments has been linked to a low propensity for apoptosis. Autophagy is a response of cancer cells to IR or chemotherapy, and involves the prominent formation of autophagic vacuoles in the cytoplasm. In this review, the synergistic effects of TCM and radiotherapy are summarized and the underlying mechanisms are illustrated, providing new therapeutic strategies for cancer.

Enhanced Ca2+ entry, ceramide formation, and apoptotic death of erythrocytes triggered by plumbagin

Plumbagin (5-hydroxy-2-methyl-1,4-naphthoquinone, 1), a natural product from plants with potential anticancer potency, induces apoptosis. Mechanisms involved in 1-induced apoptosis include mitochondrial depolarization, inactivation of NF-κB, and altered expression of anti- and proapoptotic Bcl proteins. Similar to nucleated cells, erythrocytes may undergo suicidal death or eryptosis, which, like apoptosis, results in cell shrinkage and cell membrane scrambling with phosphatidylserine exposure at the cell surface. Triggers of eryptosis include increase of cytosolic Ca(2+) activity ([Ca(2+)]i) and ceramide formation. The present study explored whether 1 stimulates eryptosis. Cell volume was estimated from forward scatter, phosphatidylserine exposure from annexin-V-binding, hemolysis from hemoglobin release, [Ca(2+)]i from Fluo-3 fluorescence, and ceramide abundance utilizing antibodies. A 48 h exposure to 1 (2 μM) decreased forward scatter and increased annexin-V-binding significantly, events paralleled by increased [Ca(2+)]i and ceramide formation. Exposure to 1 was followed by a slight but significant increase of hemolysis. Removal of extracellular Ca(2+) slightly, but significantly blunted the effect of 1 (2 μM) on annexin-V-binding. The present observations demonstrate that 1 may trigger suicidal death of erythrocytes, cells devoid of mitochondria and nuclei.

Plumbagin, a plant derived natural agent inhibits the growth of pancreatic cancer cells in in vitro and in vivo via targeting EGFR, Stat3 and NF-κB signaling pathways

Pancreatic cancer (PC) is the most aggressive malignant disease, ranks as the fourth most leading cause of cancer-related death among men and women in the United States. We present here that plumbagin (PL), a quinoid constituent isolated from the roots of the medicinal plant Plumbago zeylanica L, inhibits the growth of PC cells both in vitro and in vivo model systems. PL treatment induces apoptosis and inhibits cell viability of PC cells (PANC1, BxPC3 and ASPC1). In addition, i.p. administration of PL (2 mg/kg body weight, 5 days a week) in severe combined immunodeficiency (SCID) mice beginning 3 days after ectopic implantation of PANC1 cells resulted in a significant (P < 0.01) inhibition of both tumor weight and volume. PL treatment inhibited (1) constitutive expression of epidermal growth factor receptor (EGFR), pStat3Tyr705 and pStat3Ser727, (2) DNA binding of Stat3 and (3) physical interaction of EGFR with Stat3, in both cultured PANC1 cells and their xenograft tumors. PL treatment also inhibited phosphorylation and DNA-binding activity of NF-κB in both cultured PC cells (PANC1 and ASPC1) and in PANC1 cells xenograft tumors. Downstream target genes (cyclin D1, MMP9 and Survivin) of Stat3 and NF-κB were similarly inhibited. These results suggest that PL may be used as a novel therapeutic agent against human PC. Published 2012 Wiley-Liss, Inc. This article is a US Government work, and, as such, is in the public domain in the United States of America.

Plumbagin inhibits prostate cancer development in TRAMP mice via targeting PKCε, Stat3 and neuroendocrine markers

Plumbagin (PL), 5-hydroxy-2-methyl-1,4-naphthoquinone, is a quinoid constituent isolated from the roots of the medicinal plant Plumbago zeylanica L. (also known as chitrak). PL has also been found in Juglans regia (English Walnut), Juglans cinerea (whitenut) and Juglans nigra (blacknut). The roots of P. zeylanica have been used in Indian and Chinese systems of medicine for more than 2500 years for the treatment of various types of ailments. We were the first to report that PL inhibits the growth and invasion of hormone refractory prostate cancer (PCa) cells [Aziz,M.H. et al. (2008) Plumbagin, a medicinal plant-derived naphthoquinone, is a novel inhibitor of the growth and invasion of hormone-refractory prostate cancer. Cancer Res., 68, 9024-9032.]. Now, we present that PL inhibits in vivo PCa development in the transgenic adenocarcinoma of mouse prostate (TRAMP). PL treatment (2 mg/kg body weight i.p. in 0.2 ml phosphate-buffered saline, 5 days a week) to FVB-TRAMP resulted in a significant (P < 0.01) decrease in prostate tumor size and urogenital apparatus weights at 13 and 20 weeks. Histopathological analysis revealed that PL treatment inhibited progression of prostatic intraepithelial neoplasia (PIN) to poorly differentiated carcinoma (PDC). No animal exhibited diffuse tumor formation in PL-treated group at 13 weeks, whereas 75% of the vehicle-treated mice elicited diffuse PIN and large PDC at this stage. At 20 weeks, 25% of the PL-treated animals demonstrated diffuse PIN and 75% developed small PDC, whereas 100% of the vehicle-treated mice showed large PDC. PL treatment inhibited expression of protein kinase C epsilon (PKCε), signal transducers and activators of transcription 3 phosphorylation, proliferating cell nuclear antigen and neuroendocrine markers (synaptophysin and chromogranin-A) in excised prostate tumor tissues. Taken together, these results further suggest PL could be a novel chemopreventive agent against PCa.

The natural anticancer agent plumbagin induces potent cytotoxicity in MCF-7 human breast cancer cells by inhibiting a PI-5 kinase for ROS generation

Drug-induced haploinsufficiency (DIH) in yeast has been considered a valuable tool for drug target identification. A plant metabolite, plumbagin, has potent anticancer activity via reactive oxygen species (ROS) generation. However, the detailed molecular targets of plumbagin for ROS generation are not understood. Here, using DIH and heterozygous deletion mutants of the fission yeast Schizosaccharomyces pombe, we identified 1, 4-phopshatidylinositol 5-kinase (PI5K) its3 as a new molecular target of plumbagin for ROS generation. Plumbagin showed potent anti-proliferative activity (GI(50); 10 µM) and induced cell elongation and septum formation in wild-type S. pombe. Furthermore, plumbagin dramatically increased the intracellular ROS level, and pretreatment with the ROS scavenger, N-acetyl cysteine (NAC), protected against growth inhibition by plumbagin, suggesting that ROS play a crucial role in the anti-proliferative activity in S. pombe. Interestingly, significant DIH was observed in an its3-deleted heterozygous mutant, in which ROS generation by plumbagin was higher than that in wild-type cells, implying that its3 contributes to ROS generation by plumbagin in this yeast. In MCF7 human breast cancer cells, plumbagin significantly decreased the level of a human ortholog, 1, 4-phopshatidylinositol 5-kinase (PI5K)-1B, of yeast its3, and knockdown of PI5K-1B using siPI5K-1B increased the ROS level and decreased cell viability. Taken together, these results clearly show that PI5K-1B plays a crucial role in ROS generation as a new molecular target of plumbagin. Moreover, drug target screening using DIH in S. pombe deletion mutants is a valuable tool for identifying molecular targets of anticancer agents.

Eriocalyxin B induces apoptosis and cell cycle arrest in pancreatic adenocarcinoma cells through caspase- and p53-dependent pathways

Pancreatic cancer is difficult to detect early and responds poorly to chemotherapy. A breakthrough in the development of new therapeutic agents is urgently needed. Eriocalyxin B (EriB), isolated from the Isodon eriocalyx plant, is an ent-kaurane diterpenoid with promise as a broad-spectrum anti-cancer agent. The anti-leukemic activity of EriB, including the underlying mechanisms involved, has been particularly well documented. In this study, we demonstrated for the first time EriB's potent cytotoxicity against four pancreatic adenocarcinoma cell lines, namely PANC-1, SW1990, CAPAN-1, and CAPAN-2. The effects were comparable to that of the chemotherapeutic camptothecin (CAM), but with much lower toxicity against normal human liver WRL68 cells. EriB's cytoxicity against CAPAN-2 cells was found to involve caspase-dependent apoptosis and cell cycle arrest at the G2/M phase. Moreover, the p53 pathway was found to be activated by EriB in these cells. Furthermore, in vivo studies showed that EriB inhibited the growth of human pancreatic tumor xenografts in BALB/c nude mice without significant secondary adverse effects. These results suggest that EriB should be considered a candidate for pancreatic cancer treatment.

Cytotoxicity of naphthoquinones and their capacity to generate reactive oxygen species is quenched when conjugated with gold nanoparticles

Several reports have demonstrated the anticancer activities of plumbagin, a naphthoquinone derivative isolated from plants belonging to Plumbaginaceae family. However, to the best of our knowledge, there are no reports which describe gold nanoconjugation with plumbagin, even though plumbagin is considered to be a promising therapeutic agent. In this report, we demonstrate the fabrication and characterization of gold nanoparticles conjugated with plumbagin (AuPB) that can reduce the toxicity of the latter, and their capacity for cellular localization and generation of reactive oxygen species. The anticancer activity and ability of plumbagin to produce reactive oxygen species was studied and compared with that of bromoderivatives of 1,4 naphthoquinones such as 2-bromo-1,4-naphthoquinone (2-BNQ) and 2,3-dibromo-1, 4-naphthoquinone (2,3-DBNQ) and their gold nanoconjugates. Plumbagin and bromoderivatives of 1,4 naphthoquinones in the form of gold nanoconjugates showed reduced cytotoxicity and apoptosis compared with the pristine compounds, ie, plumbagin, 2-BNQ, and 2,3-DBNQ. Interestingly, we observed that the gold nanoparticles could quench the reactive oxygen species-generating capacity of plumbagin, 2-BNQ, and 2,3-BNQ, which is one of the main mechanisms of action of the naphthoquinones. Therefore, it can be concluded that conjugation with gold nanoparticles can reduce the cytotoxicity of these compounds.

Plumbagin inhibits invasion and migration of breast and gastric cancer cells by downregulating the expression of chemokine receptor CXCR4

Background

Increasing evidence indicates that the interaction between the CXC chemokine receptor-4 (CXCR4) and its ligand CXCL12 is critical in the process of metastasis that accounts for more than 90% of cancer-related deaths. Thus, novel agents that can downregulate the CXCR4/CXCL12 axis have therapeutic potential in inhibiting cancer metastasis.

Methods

In this report, we investigated the potential of an agent, plumbagin (5-hydroxy-2-methyl-1, 4-naphthoquinone), for its ability to modulate CXCR4 expression and function in various tumor cells using Western blot analysis, DNA binding assay, transient transfection, real time PCR analysis, chromatin immunoprecipitation, and cellular migration and invasion assays.

Results

We found that plumbagin downregulated the expression of CXCR4 in breast cancer cells irrespective of their HER2 status. The decrease in CXCR4 expression induced by plumbagin was not cell type-specific as the inhibition also occurred in gastric, lung, renal, oral, and hepatocellular tumor cell lines. Neither proteasome inhibition nor lysosomal stabilization had any effect on plumbagin-induced decrease in CXCR4 expression. Detailed study of the underlying molecular mechanism(s) revealed that the regulation of the downregulation of CXCR4 was at the transcriptional level, as indicated by downregulation of mRNA expression, inhibition of NF-κB activation, and suppression of chromatin immunoprecipitation activity. In addition, using a virtual, predictive, functional proteomics-based tumor pathway platform, we tested the hypothesis that NF-κB inhibition by plumbagin causes the decrease in CXCR4 and other metastatic genes. Suppression of CXCR4 expression by plumbagin was found to correlate with the inhibition of CXCL12-induced migration and invasion of both breast and gastric cancer cells.

Conclusions

Overall, our results indicate, for the first time, that plumbagin is a novel blocker of CXCR4 expression and thus has the potential to suppress metastasis of cancer.

Effects of phytochemicals on ionization radiation-mediated carcinogenesis and cancer therapy

Ionizing radiation (IR)-induced cellular damage is implicated in carcinogenesis as well as therapy of cancer. Advances in radiation therapy have led to the decrease in dosage and localizing the effects to the tumor; however, the development of radioresistance in cancer cells and radiation toxicity to normal tissues are still the major concerns. The development of radioresistance involves several mechanisms, including the activation of mitogenic and survival signaling, induction of DNA repair, and changes in redox signaling and epigenetic regulation. The current strategy of combining radiation with standard cytotoxic chemotherapeutic agents can potentially lead to unwanted side effects due to both agents. Thus agents are needed that could improve the efficacy of radiation killing of cancer cells and prevent the damage to normal cells and tissues caused by the direct and bystander effects of radiation, without have its own systemic toxicity. Chemopreventive phytochemicals, usually non-toxic agents with both cancer preventive and therapeutic activities, could rightly fit in this approach. In this regard, naturally occurring compounds, including curcumin, parthenolide, genistein, gossypol, ellagic acid, withaferin, plumbagin and resveratrol, have shown considerable potential. These agents suppress the radiation-induced activation of receptor tyrosine kinases and nuclear factor-κB signaling, can modify cell survival and DNA repair efficacy, and may potentiate ceramide signaling. These radiosensitizing and counter radioresistance mechanisms of phytochemicals in cancer cells are also associated with changes in epigenetic gene regulation. Because radioresistance involves multiple mechanisms, more studies are needed to discover novel phytochemicals having multiple mechanisms of radiosensitization and to overcome radioresistance of cancer cells. Pre-clinical studies are needed to address the appropriate dosage, timing, and duration of the application of phytochemicals with radiation to justify clinical trials. Nonetheless, some phytochemicals in combination with IR may play a significant role in enhancing the therapeutic index of cancer treatment.

Perspectives on medicinal properties of plumbagin and its analogs

Plumbagin is one of the simplest plant secondary metabolite of three major phylogenic families viz. Plumbaginaceae, Droseraceae, and Ebenceae, and exhibits highly potent biological activities, including antioxidant, antiinflammatory, anticancer, antibacterial, and antifungal activities. Recent investigations indicate that these activities arise mainly out of its ability to undergo redox cycling, generating reactive oxygen species and chelating trace metals in biological system. The compound is endowed with a property to inhibit the drug efflux mechanism in drug-resistant bacteria, thereby allowing intracellular accumulation of the potent drug molecules. An interesting bioactivity exhibited by this compound is the elimination of stringent, conjugative, multidrug-resistant plasmids from several bacterial strains including opportunistic bacteria, such as Acinetobacter baumannii. Moreover, plumbagin effectively induces apoptosis and causes cell cycle arrest, which is, in part, due to the inactivation of NF-κB in cancer cells. Therefore, it has been suggested that designing "hybrid drug molecules" of plumbagin by combining it with other appropriate anticancer agents may lead to the generation of novel and potent anticancer drugs with pleiotropic action against human cancers. This comprehensive review is an attempt to understand the chemistry of plumbagin and catalog its biological activities reported to date.