Inhibition of DNA Topoisomerase I by Natural and Synthetic Mono- and Dimeric Protoberberine Alkaloids

Berberine: Pharmacological Features in Health, Disease and Aging

BACKGROUND

Berberine is the main active compound of different herbs and is defined as an isoquinoline quaternary botanical alkaloid found in barks and roots of numerous plants. It exhibits a wide range of pharmacological effects, such as anti-obesity and antidiabetic effects. Berberine has antibacterial activity against a variety of microbiota, including many bacterial species, protozoa, plasmodia, fungi, and trypanosomes.

OBJECTIVE

This review describes the role of berberine and its metabolic effects. It also discusses how it plays a role in glucose metabolism, fat metabolism, weight loss, how it modulates the gut microbiota, and what are its antimicrobial properties along with its potential side effects with maximal tolerable dosage.

METHODS

Representative studies were considered and analyzed from different scientific databases, including PubMed and Web of Science, for the years 1982-2022.

RESULTS

Literature analysis shows that berberine affects many biochemical and pharmacological pathways that theoretically yield a positive effect on health and disease. Berberine exhibits neuroprotective properties in various neurodegenerative and neuropsychological ailments. Despite its low bioavailability after oral administration, berberine is a promising tool for several disorders. A possible hypothesis would be the modulation of the gut microbiome. While the evidence concerning the aging process in humans is more limited, preliminary studies have shown positive effects in several models.

CONCLUSION

Berberine could serve as a potential candidate for the treatment of several diseases. Previous literature has provided a basis for scientists to establish clinical trials in humans. However, for obesity, the evidence appears to be sufficient for hands-on use.

Di-berberine conjugates as chemical probes of Pseudomonas aeruginosa MexXY-OprM efflux function and inhibition

The Resistance-Nodulation-Division (RND) efflux pump superfamily is pervasive among Gram-negative pathogens and contributes extensively to clinical antibiotic resistance. The opportunistic pathogen Pseudomonas aeruginosa contains 12 RND-type efflux systems, with four contributing to resistance including MexXY-OprM which is uniquely able to export aminoglycosides. At the site of initial substrate recognition, small molecule probes of the inner membrane transporter (e.g., MexY) have potential as important functional tools to understand substrate selectivity and a foundation for developing adjuvant efflux pump inhibitors (EPIs). Here, we optimized the scaffold of berberine, a known but weak MexY EPI, using an in-silico high-throughput screen to identify di-berberine conjugates with enhanced synergistic action with aminoglycosides. Further, docking and molecular dynamics simulations of di-berberine conjugates reveal unique contact residues and thus sensitivities of MexY from distinct P. aeruginosa strains. This work thereby reveals di-berberine conjugates to be useful probes of MexY transporter function and potential leads for EPI development.

Current understanding and future prospects on Berberine for anticancer therapy

Berberine (BBR) is a potential plant metabolite and has remarkable anticancer properties. Many kinds of research are being focused on the cytotoxic activity of berberine in in vitro and in vivo studies. A variety of molecular targets which lead to the anticancer effect of berberine ranges from p-53 activation, Cyclin B expression for arresting cell cycles; protein kinase B (AKT), MAP kinase and IKB kinase for antiproliferative activity; effect on beclin-1 involved in autophagy; reduced expression of MMP-9 and MMP-2 for the inhibition of invasion and metastasis etc. Berberine also interferes with transcription factor-1 (AP-1) activity responsible for the expression of oncogenes and neoplastic transformation of the cell. It also leads to the inhibition of various enzymes which are directly or indirectly involved in carcinogenesis like N acetyl transferase, Cyclo-oxygenase-2, Telomerase and Topoisomerase. In addition to these actions, Berberine plays a role in, the regulation of reactive oxygen species and inflammatory cytokines in preventing cancer formation. Berberine anticancer properties are demonstrated due to the interaction of berberine with micro-RNA. The summarized information presented in this review article may help and lead the researchers, scientists/industry persons to use berberine as a promising candidate against cancer.

Structural modifications of berberine and their binding effects towards polymorphic deoxyribonucleic acid structures: A review

Berberine (BBR) is a plant derived quaternary benzylisoquinoline alkaloid, which has been widely used in traditional medicines for a long term. It possesses broad pharmacological effects and is widely applied in clinical. In recent years, the anti-tumor effects of BBR have attracted more and more attention of the researchers. The canonical right-handed double-stranded helical deoxyribonucleic acid (B-DNA) and its polymorphs occur under various environmental conditions and are involved in a plethora of genetic instability-related diseases especially tumor. BBR showed differential binding effects towards various polymorphic DNA structures. But its poor lipophilicity and fast metabolism limited its clinical utility. Structural modification of BBR is an effective approach to improve its DNA binding activity and bioavailability in vivo. A large number of studies dedicated to improving the binding affinities of BBR towards different DNA structures have been carried out and achieved tremendous advancements. In this article, the main achievements of BBR derivatives in polymorphic DNA structures binding researches in recent 20 years were reviewed. The structural modification strategy of BBR, the DNA binding effects of its derivatives, and the structure activity relationship (SAR) analysis have also been discussed.

Dimeric Drugs

This review intends to summarize the structures of an extensive number of symmetrical-dimeric drugs, having two monomers linked via a bridging entity while emphasizing the large versatility of biologically active substances reported to possess dimeric structures. The largest number of classes of these compounds consist of anticancer agents, antibiotics/antimicrobials, and anti-AIDS drugs. Other symmetrical-dimeric drugs include antidiabetics, antidepressants, analgesics, anti-inflammatories, drugs for the treatment of Alzheimer's disease, anticholesterolemics, estrogenics, antioxidants, enzyme inhibitors, anti-Parkisonians, laxatives, antiallergy compounds, cannabinoids, etc. Most of the articles reviewed do not compare the activity/potency of the dimers to that of their corresponding monomers. Only in limited cases, various suggestions have been made to justify unexpected higher activity of the dimers vs. the corresponding monomers. These suggestions include statistical effects, the presence of dimeric receptors, binding of a dimer to two receptors simultaneously, and others. It is virtually impossible to predict which dimers will be preferable to their respective monomers, or which linking bridges will lead to the most active compounds. It is expected that the extensive number of articles summarized, and the large variety of substances mentioned, which display various biological activities, should be of interest to many academic and industrial medicinal chemists.

Synthesis and In Vitro Photocytotoxicity of 9-/13-Lipophilic Substituted Berberine Derivatives as Potential Anticancer Agents

The objective of this study was to synthesize the 9-/13-position substituted berberine derivatives and evaluate their cytotoxic and photocytotoxic effects against three human cancer cell lines. Among all the synthesized compounds, 9-O-dodecyl- (5e), 13-dodecyl- (6e), and 13-O-dodecyl-berberine (7e) exhibited stronger growth inhibition against three human cancer cell lines, (HepG2, HT-29 and BFTC905), in comparison with structurally related berberine (1). These three compounds also showed the photocytotoxicity in human cancer cells in a concentration-dependent and light dose-dependent manner. Through flow cytometry analysis, we found out a lipophilic group at the 9-/13-position of berberine may have facilitated its penetration into test cells and hence enhanced its photocytotoxicity on the human liver cancer cell HepG2. Further, in cell cycle analysis, 5e, 6e, and 7e induced HepG2 cells to arrest at the S phase and caused apoptosis upon irradiation. In addition, photodynamic treatment of berberine derivatives 5e, 6e, and 7e again showed a significant photocytotoxic effects on HepG2 cells, induced remarkable cell apoptosis, greatly increased intracellular ROS level, and the loss of mitochondrial membrane potential. These results over and again confirmed that berberine derivatives 5e, 6e, and 7e greatly enhanced photocytotoxicity. Taken together, the test data led us to conclude that berberine derivatives with a dodecyl group at the 9-/13-position could be great candidates for the anti-liver cancer medicines developments.

Abilities of berberine and chemically modified berberines to interact with metformin and inhibit proliferation of pancreatic cancer cells

Pancreatic cancer is devastating cancer worldwide with few if any truly effective therapies. Pancreatic cancer has an increasing incidence and may become the second leading cause of death from cancer. Novel, more effective therapeutic approaches are needed as pancreatic cancer patients usually survive for less than a year after being diagnosed. Control of blood sugar levels by the prescription drug metformin in diseases such as diabetes mellitus has been examined in association with pancreatic cancer. While the clinical trials remain inconclusive, there is hope that certain diets and medications may affect positively the outcomes of patients with pancreatic and other cancers. Other natural compounds may share some of the effects of metformin. One "medicinal" fruit consumed by millions worldwide is berberine (BBR). Metformin and BBR both activate AMP-activated protein kinase (AMPK) which is a key mediator of glucose metabolism. Glucose metabolism has been shown to be very important in cancer and its significance is increasing. In the following studies, we have examined the effects of metformin, BBR and a panel of modified BBRs (NAX compounds) and chemotherapeutic drugs on the growth of four different human pancreatic adenocarcinoma cell lines (PDAC). Interestingly, the effects of metformin could be enhanced by BBR and certain modified BBRs. Upon restoration of WT-TP53 activity in MIA-PaCa-2 cells, an altered sensitivity to the combination of certain NAX compounds and metformin was observed compared to the parental cells which normally lack WT-TP53. Certain NAX compounds may interact with WT-TP53 and metformin treatment to alter the expression of key molecules involved in cell growth. These results suggest a therapeutic approach by combining certain pharmaceutical drugs and nutraceuticals to suppress the growth of cancer cells.

Synthesis and Anticancer Activity of 9-O-Pyrazole Alkyl Substituted Berberine Derivatives

BACKGROUND

Berberine (BBR), an isoquinoline plant alkaloid isolated from plants such as Coptis chinensis and Hydrastis canadensis, own multiple pharmacological activities.

OBJECTIVE

In this study, seven BBR derivatives were synthesized and their anticancer activity against HeLa cervical and A549 human lung cancer cell lines were evaluated in vitro.

METHODS

The anti-cancer activity was measured by MTT assay, and apoptosis was demonstrated by the annexin V-FITC/PI staining assay. The intracellular oxidative stress was investigated through DCFH-DA assay. The molecular docking study was carried out in molecular operating environment (MOE).

RESULTS

Compound B3 and B5 showed enhanced anti-cancer activity compared with BBR, the IC50 for compound B3 and B5 were significantly lower than BBR, and compound B3 at the concentration of 64 or 128 µM induced apoptosis in HeLa and A549 cell lines. The reactive oxygen species (ROS) was generated in both cell lines when treated with 100 µM of all the compounds, and compound B3 and B5 induced higher activity in the generation of ROS, while compound B3 exhibited the highest activity, these results are in accordance with the cytotoxicity results, indicating the cytotoxicity were mostly generated from the oxidative stress. In addition, molecular docking analysis showed that compound B3 had the greatest affinity with Hsp90. Upon binding, the protective function of Hsp90 was lost, which might explain its higher cytotoxicity from molecular interaction aspect.

CONCLUSION

All the results demonstrated that compound B3 and B5 showed significantly higher anti-cancer ability than BBR, and compound B3 is a promising anticancer drug candidate.

A comprehensive review of topoisomerase inhibitors as anticancer agents in the past decade

The topoisomerase enzymes play an important role in DNA metabolism, and searching for enzyme inhibitors is an important target in the search for new anticancer drugs. Discovery of new anticancer chemotherapeutical capable of inhibiting topoisomerase enzymes is highlighted in anticancer research. Therefore, biologists, organic chemists and medicinal chemists all around the world have been identifying, designing, synthesizing and evaluating a variety of novel bioactive molecules targeting topoisomerase. This review summarizes types of topoisomerase inhibitors in the past decade, and divides them into nine classes by structural characteristics, including N-heterocycles compounds, quinone derivatives, flavonoids derivatives, coumarin derivatives, lignan derivatives, polyphenol derivatives, diterpenes derivatives, fatty acids derivatives, and metal complexes. Then we discussed the application prospect and development of these anticancer compounds, as well as concluded parts of their structural-activity relationships. We believe this review would be invaluable in helping to further search potential topoisomerase inhibition as antitumor agent in clinical usage.

Abilities of berberine and chemically modified berberines to inhibit proliferation of pancreatic cancer cells

Berberine (BBR) is a common nutraceutical consumed by millions worldwide. BBR has many different effects on human health, e.g., diabetes, diarrhea, inflammation and now more recently it has been proposed to have potent anti-cancer effects. BBR has been shown to suppress the growth of cancer cells more than normal cells. BBR has been proposed to exert its growth-inhibitory effects by many different biochemical mechanisms including: suppression of cell cycle progression, induction of reactive oxygen species, induction of apoptosis and autophagy and interactions with DNA potentially leading to DNA damage, and altered gene expression. Pancreatic cancer is a leading cancer worldwide associated with a poor prognosis. As our population ages, pancreatic cancer has an increasing incidence and will likely become the second leading cause of death from cancer. There are few truly-effective therapeutic options for pancreatic cancer. Surgery and certain chemotherapeutic drugs are used to treat pancreatic cancer patients. Novel approaches to treat pancreatic cancer patients are direly needed as they usually survive for less than a year after being diagnosed. In the following manuscript, we discuss the abilities of BBR and certain chemically-modified BBRs (NAX compounds) to suppress growth of pancreatic cancer cells.

Glycoside hydrolase family 18 and 20 enzymes are novel targets of the traditional medicine berberine

Berberine is a traditional medicine that has multiple medicinal and agricultural applications. However, little is known about whether berberine can be a bioactive molecule toward carbohydrate-active enzymes, which play numerous vital roles in the life process. In this study, berberine and its analogs were discovered to be competitive inhibitors of glycoside hydrolase family 20 β-N-acetyl-d-hexosaminidase (GH20 Hex) and GH18 chitinase from both humans and the insect pest Ostrinia furnacalis Berberine and its analog SYSU-1 inhibit insect GH20 Hex from O. furnacalis (OfHex1), with K_i values of 12 and 8.5 μm, respectively. Co-crystallization of berberine and its analog SYSU-1 in complex with OfHex1 revealed that the positively charged conjugate plane of berberine forms π-π stacking interactions with Trp⁴⁹⁰, which are vital to its inhibitory activity. Moreover, the 1,3-dioxole group of berberine binds an unexplored pocket formed by Trp³²², Trp⁴⁸³, and Val⁴⁸⁴, which also contributes to its inhibitory activity. Berberine was also found to be an inhibitor of human GH20 Hex (HsHexB), human GH18 chitinase (HsCht and acidic mammalian chitinase), and insect GH18 chitinase (OfChtI). Besides GH18 and GH20 enzymes, berberine was shown to weakly inhibit human GH84 O-GlcNAcase (HsOGA) and Saccharomyces cerevisiae GH63 α-glucosidase I (ScGluI). By analyzing the published crystal structures, berberine was revealed to bind with its targets in an identical mechanism, namely via π-π stacking and electrostatic interactions with the aromatic and acidic residues in the binding pockets. This paper reports new molecular targets of berberine and may provide a berberine-based scaffold for developing multitarget drugs.

Metformin influences drug sensitivity in pancreatic cancer cells

Pancreatic ductal adenocarcinoma (PDAC) is an aggressive, highly metastatic malignancy and accounts for 85% of pancreatic cancers. PDAC patients have poor prognosis with a five-year survival of only 5-10% after diagnosis and treatment. Pancreatic cancer has been associated with type II diabetes as the frequency of recently diagnosed diabetics that develop pancreatic cancer within a 10-year period of initial diagnosis of diabetes in increased in comparison to non-diabetic patients. Metformin is a very frequently prescribed drug used to treat type II diabetes. Metformin acts in part by stimulating AMP-kinase (AMPK) and results in the suppression of mTORC1 activity and the induction of autophagy. In the following studies, we have examined the effects of metformin in the presence of various chemotherapeutic drugs, signal transduction inhibitors and natural products on the growth of three different PDAC lines. Metformin, by itself, was not effective at suppressing growth of the pancreatic cancer cell lines at concentration less than 1000 nM, however, in certain PDAC lines, a suboptimal dose of metformin (250 nM) potentiated the effects of various chemotherapeutic drugs used to treat pancreatic cancer (e.g., gemcitabine, cisplatin, 5-fluorouracil) and other cancer types (e.g., doxorubicin, docetaxel). Furthermore, metformin could increase anti-proliferative effects of mTORC1 and PI3K/mTOR inhibitors as well as natural products such as berberine and the anti-malarial drug chloroquine in certain PDAC lines. Thus, metformin can enhance the effects of certain drugs and signal transduction inhibitors which are used to treat pancreatic and various other cancers.

Effects of resveratrol, curcumin, berberine and other nutraceuticals on aging, cancer development, cancer stem cells and microRNAs

Natural products or nutraceuticals have been shown to elicit anti-aging, anti-cancer and other health-enhancing effects. A key target of the effects of natural products may be the regulation of microRNA (miR) expression which results in cell death or prevents aging, diabetes, cardiovascular and other diseases. This review will focus on a few natural products, especially on resveratrol (RES), curcumin (CUR) and berberine (BBR). RES is obtained from the skins of grapes and other fruits and berries. RES may extend human lifespan by activating the sirtuins and SIRT1 molecules. CUR is isolated from the root of turmeric (Curcuma longa). CUR is currently used in the treatment of many disorders, especially in those involving an inflammatory process. CUR and modified derivatives have been shown to have potent anti-cancer effects, especially on cancer stem cells (CSC). BBR is also isolated from various plants (e.g., Coptis chinensis) and has been used for centuries in traditional medicine to treat diseases such as adult- onset diabetes. Understanding the benefits of these and other nutraceuticals may result in approaches to improve human health.

Effects of berberine, curcumin, resveratrol alone and in combination with chemotherapeutic drugs and signal transduction inhibitors on cancer cells-Power of nutraceuticals

Over the past fifty years, society has become aware of the importance of a healthy diet in terms of human fitness and longevity. More recently, the concept of the beneficial effects of certain components of our diet and other compounds, that are consumed often by different cultures in various parts of the world, has become apparent. These "healthy" components of our diet are often referred to as nutraceuticals and they can prevent/suppress: aging, bacterial, fungal and viral infections, diabetes, inflammation, metabolic disorders and cardiovascular diseases and have other health-enhancing effects. Moreover, they are now often being investigated because of their anti-cancer properties/potentials. Understanding the effects of various natural products on cancer cells may enhance their usage as anti-proliferative agents which may be beneficial for many health problems. In this manuscript, we discuss and demonstrate how certain nutraceuticals may enhance other anti-cancer drugs to suppress proliferation of cancer cells.

Synthesis and evaluation of novel 12-aryl berberine analogues with hypoxia-inducible factor-1 inhibitory activity

Seven novel 12-phenyl berberines (3a–3f, 3k) showed more potent inhibitory effect on hypoxia-induced HIF-1 transcriptional activity than the parent berberine.

The dual topoisomerase inhibitor A35 preferentially and specially targets topoisomerase 2α by enhancing pre-strand and post-strand cleavage and inhibiting DNA religation

DNA topoisomerases play a key role in tumor proliferation. Chemotherapeutics targeting topoisomerases have been widely used in clinical oncology, but resistance and side effects, particularly cardiotoxicity, usually limit their application. Clinical data show that a decrease in topoisomerase (top) levels is the primary factor responsible for resistance, but in cells there is compensatory effect between the levels of top1 and top2α. Here, we validated cyclizing-berberine A35, which is a dual top inhibitor and preferentially targets top2α. The impact on the top2α catalytic cycle indicated that A35 could intercalate into DNA but did not interfere with DNA-top binding and top2α ATPase activity. A35 could facilitate DNA-top2α cleavage complex formation by enhancing pre-strand and post-strand cleavage and inhibiting religation, suggesting this compound can be a topoisomerase poison and had a district mechanism from other topoisomerase inhibitors. TARDIS and comet assays showed that A35 could induce cell DNA breakage and DNA-top complexes but had no effect on the cardiac toxicity inducer top2β. Silencing top1 augmented DNA break and silencing top2α decreased DNA break. Further validation in H9c2 cardiac cells showed A35 did not disturb cell proliferation and mitochondrial membrane potency. Additionally, an assay with nude mice further demonstrated A35 did not damage the heart. Our work identifies A35 as a novel skeleton compound dually inhibits topoisomerases, and predominantly and specially targets top2α by interfering with all cleavage steps and its no cardiac toxicity was verified by cardiac cells and mice heart. A35 could be a novel and effective targeting topoisomerase agent.

Pharmacological effects of berberine and its derivatives: a patent update

INTRODUCTION

A number of plant-derived agents are used in many therapeutic areas. Berberine, an important protoberberine alkaloid, is present in a number of medicinal plants that have been widely used in traditional Chinese medicine for hundreds of years. Modern research has shown that berberine and its derivatives display several pharmacological effects through various mechanisms.

AREAS COVERED

This review discusses recent and mostly Chinese patents that report the synthesis of berberine, berberine derivatives and berberine salts, and methods of preparation for formulations (traditional Chinese medicine) containing herbal components rich in berberine, along with their applications. The review covers several therapeutic effects of berberine, its derivatives and pharmaceutical formulations against cancer, obesity, diabetes, inflammation, atherosclerosis, Alzheimer's disease, rheumatoid arthritis and cardiovascular diseases. In addition, the mechanisms underlying the pharmacological effects are discussed.

EXPERT OPINION

Modification of the functional groups of berberine has a significant effect on the pharmacological activity. However, studies on altering the atoms and size of the berberine skeleton are rare. Thus, it may be beneficial to initiate a drug development program focused on inserting heterocyclic rings of different sizes into berberine. Furthermore, structural modification to improve the safety, efficacy and selectivity is necessary to promote the use of berberine-based drugs in clinical settings.

Determination of cytotoxicity of traditional Chinese medicine herbs, Rhizoma coptidis, Radix scutellariae, and Cortex phellodendri, by three methods

BACKGROUND

Many herbs are used in traditional Chinese medicine TCM) for treatment of infections but their properties, in particular, their effects on normal cells have received little attention. This study investigated the cytotoxic properties of three TCM herbs with potential use in prevention and treatment of ocular infections, including Acanthamoeba keratitis.

METHOD

The study investigated cytotoxic effects of the herbal extracts of Rhizoma coptidis, Radix scutellariae, and Cortex phellodendri on human corneal epithelial cells using trypan blue staining, MTT production, and flow cytometry. Differences between herbs were determined using repeated measures one-way analysis of variance, followed by paired t-tests where appropriate.

RESULTS

These three herbs appeared to lack cytotoxicity when tested with trypan blue and MTT, but flow cytometry revealed that R. coptidis led to cell membrane damage.

CONCLUSION

Lack of cytotoxicity of R. scutellariae and C. phellodendri extracts suggest that these are potentially suitable for use in ocular preparations. Only flow cytometry was able to accurately predict cytotoxic effects of extracts of TCM herbs on HCEC, demonstrating the importance of using a sensitive method of detection of cytotoxicity.

Current knowledge and pharmacological profile of berberine: An update

Berberine, a benzylisoquinoline alkaloid, occurs as an active constituent in numerous medicinal plants and has an array of pharmacological properties. It has been used in Ayurvedic and Chinese medicine for its antimicrobial, antiprotozoal, antidiarrheal and antitrachoma activity. Moreover, several clinical and preclinical studies demonstrate ameliorative effect of berberine against several disorders including metabolic, neurological and cardiological problems. This review provides a summary regarding the pharmacokinetic and pharmacodynamic features of berberine, with a focus on the different mechanisms underlying its multispectrum activity. Studies regarding the safety profile, drug interactions and important clinical trials of berberine have also been included. Clinical trials with respect to neurological disorders need to be undertaken to exploit the beneficiary effects of berberine against serious disorders such as Alzheimer's and Parkinson's disease. Also, clinical studies to detect rare adverse effects of berberine need to be initiated to draw a complete safety profile of berberine and strengthen its applicability.

Dynamic monitoring of the cytotoxic effects of protoberberine alkaloids from Rhizoma Coptidis on HepG2 cells using the xCELLigence system

AIM

To investigate the cytotoxic effects of the six protoberberine alkaloids (PAs) from Rhizoma Coptidis on HepG2 cells.

METHOD

A systematic screening was conducted to investigate the dynamic response of HepG2 cells to the PAs using the impedance-based xCELLigence system. Cisplatin was selected as the positive control. The real time, concentration-response curves and the 50% inhibitory concentrations (IC50) were acquired to evaluate the anticancer activity of the PAs.

RESULTS

All of the six PAs inhibited cell growth and induce death in HepG2 cells in a time- and concentration-dependent manner. The IC50 values of cisplatin, berberine, columbamine, coptisine, epiberberine, jatrorrhizine, and palmatine were 5.13, 42.33, 226.54, 36.90, 302.72, 383.54, and 456.96 μg·mL(-1), respectively. The results obtained using the xCELLigence system corresponded well with those of the conventional methods.

CONCLUSION

The xCELLigence system is a reliable and efficient tool for real-time screening of the cytotoxic effect of compounds in cell-based in vitro assays. Coptisine and berberine, with methylenedioxy group at C2 and C3 on the phenyl ring showed stronger effect.than the other four PAs. However, compared with cisplatin, the six PAs didn't show obvious cytotoxic effect on HepG2 cells. These results provided some useful data for the evaluation of the anticancer compounds, and the clinical application of traditional Chinese medicine.

Structure-based virtual screening of novel natural alkaloid derivatives as potential binders of h-telo and c-myc DNA G-quadruplex conformations

Several ligands can bind to the non-canonical G-quadruplex DNA structures thereby stabilizing them. These molecules can act as effective anticancer agents by stabilizing the telomeric regions of DNA or by regulating oncogene expression. In order to better interact with the quartets of G-quadruplex structures, G-binders are generally characterized by a large aromatic core involved in π-π stacking. Some natural flexible cyclic molecules from Traditional Chinese Medicine have shown high binding affinity with G-quadruplex, such as berbamine and many other alkaloids. Using the structural information available on G-quadruplex structures, we performed a high throughput in silico screening of commercially available alkaloid derivative databases by means of a structure-based approach based on docking and molecular dynamics simulations against the human telomeric sequence d[AG₃(T₂AG₃)₃] and the c-myc promoter structure. We identified 69 best hits reporting an improved theoretical binding affinity with respect to the active set. Among them, a berberine derivative, already known to remarkably inhibit telomerase activity, was related to a better theoretical affinity versusc-myc.

Berberine, an epiphany against cancer

Alkaloids are used in traditional medicine for the treatment of many diseases. These compounds are synthesized in plants as secondary metabolites and have multiple effects on cellular metabolism. Among plant derivatives with biological properties, the isoquinoline quaternary alkaloid berberine possesses a broad range of therapeutic uses against several diseases. In recent years, berberine has been reported to inhibit cell proliferation and to be cytotoxic towards cancer cells. Based on this evidence, many derivatives have been synthesized to improve berberine efficiency and selectivity; the results so far obtained on human cancer cell lines support the idea that they could be promising agents for cancer treatment. The main properties of berberine and derivatives will be illustrated.

Targets and mechanisms of berberine, a natural drug with potential to treat cancer with special focus on breast cancer

Breast cancer is the most common cancer among women worldwide and novel therapeutic agents are needed to treat this disease. The plant-based alkaloid berberine has potential therapeutic applications for breast cancer, although a better understanding of the genes and cellular pathways regulated by this compound is needed to define the mechanism of its action in cancer treatment. In this review, the molecular targets of berberine in various cancers, particularly breast cancer, are discussed. Berberine was shown to be effective in inhibiting cell proliferation and promoting apoptosis in various cancerous cells. Some signaling pathways affected by berberine, including the MAP (mitogen-activated protein) kinase and Wnt/β-catenin pathways, are critical for reducing cellular migration and sensitivity to various growth factors. This review will discuss recent studies and consider the application of new prospective approaches based on microRNAs and other crucial regulators for use in future studies to define the action of berberine in cancer. The effects of berberine on cancer cell survival and proliferation are also outlined.

Discovery, synthesis and biological evaluation of cycloprotoberberine derivatives as potential antitumor agents

A series of new 1,13-cycloprotoberberine derivatives defined through variations at the 9-position were designed, synthesized and evaluated for their cytotoxicities in human HepG2 (hepatoma), HT1080 (fibrosarcoma) and HCT116 (colon cancer) cells. The preliminary structure-activity relationship (SAR) revealed that the replacement of 9-methoxyl with an ester moiety might significantly enhance the antiproliferative activity in vitro. Notably, compound 7f demonstrated equipotent cytotoxicity activity against breast cancer MCF-7 (parent) and doxorubicin (DOX)-resistant MCF-7 (MCF-7/ADrR) cells, indicating a mode of action different from that of DOX. Further mechanism study showed that 7f significantly inhibited activity of DNA topoisomerase I (Top I) and Top II. G2/M phase arrest and tumor cell growth reduction was observed thereafter. Thus, we consider cycloprotoberberine analogues to be a new family of promising antitumor agents with an advantage of inhibiting drug-resistant cancer cells.

Mechanism study of goldenseal-associated DNA damage

Goldenseal has been used for the treatment of a wide variety of ailments including gastrointestinal disturbances, urinary tract disorders, and inflammation. The five major alkaloid constituents in goldenseal are berberine, palmatine, hydrastine, hydrastinine, and canadine. When goldenseal was evaluated by the National Toxicology Program (NTP) in the standard 2-year bioassay, goldenseal induced an increase in liver tumors in rats and mice; however, the mechanism of goldenseal-associated liver carcinogenicity remains unknown. In this study, the toxicity of the five goldenseal alkaloid constituents was characterized, and their toxic potencies were compared. As measured by the Comet assay and the expression of γ-H2A.X, berberine, followed by palmatine, appeared to be the most potent DNA damage inducer in human hepatoma HepG2 cells. Berberine and palmatine suppressed the activities of both topoisomerase (Topo) I and II. In berberine-treated cells, DNA damage was shown to be directly associated with the inhibitory effect of Topo II, but not Topo I by silencing gene of Topo I or Topo II. In addition, DNA damage was also observed when cells were treated with commercially available goldenseal extracts and the extent of DNA damage was positively correlated to the berberine content. Our findings suggest that the Topo II inhibitory effect may contribute to berberine- and goldenseal-induced genotoxicity and tumorigenicity.

Berberine inhibits the growth of human colorectal adenocarcinoma in vitro and in vivo

Berberine is an alkaloid isolated from the Chinese herbal medicine Huanglian, and has long been used as an antibiotic. Its antineoplastic properties were subsequently discovered in vitro. The purpose of this study was to investigate the effects of berberine on the growth of human colorectal carcinoma cells in vitro and in vivo. The results showed that berberine inhibited human colorectal adenocarcinoma (LoVo) cell growth in a time- and dose-dependent manner. A WST-1 assay showed that the IC50 value after 72 h was 40.79 ± 4.11 μM. Cell cycle analysis of 40 μM berberine-treated LoVo cells by flow cytometry showed accumulation of cells in the G2/M phase. The inhibition of LoVo cell growth by berberine was associated with the suppression of cyclin B1, cdc2, and cdc25c proteins. Berberine at a dose of 50 mg kg(-1) day(-1) showed inhibitory rates of 45.3% in a human colorectal adenocarcinoma xenograft in nude mice. The combination of berberine and 5-fluorouracil (5-FU) had a higher inhibitory rate (59.8%) than the berberine group (36.4%, P = 0.01), but no significant difference was observed between the 5-FU group (43.0%, P = 0.06) and the combination group. These results support the possibility that berberine may be useful as an alternative therapy for colorectal carcinoma.

Interaction of herbal compounds with biological targets: a case study with berberine

Berberine is one of the main alkaloids found in the Chinese herb Huang lian (Rhizoma Coptidis), which has been reported to have multiple pharmacological activities. This study aimed to analyze the molecular targets of berberine based on literature data followed by a pathway analysis using the PANTHER program. PANTHER analysis of berberine targets showed that the most classes of molecular functions include receptor binding, kinase activity, protein binding, transcription activity, DNA binding, and kinase regulator activity. Based on the biological process classification of in vitro berberine targets, those targets related to signal transduction, intracellular signalling cascade, cell surface receptor-linked signal transduction, cell motion, cell cycle control, immunity system process, and protein metabolic process are most frequently involved. In addition, berberine was found to interact with a mixture of biological pathways, such as Alzheimer's disease-presenilin and -secretase pathways, angiogenesis, apoptosis signalling pathway, FAS signalling pathway, Hungtington disease, inflammation mediated by chemokine and cytokine signalling pathways, interleukin signalling pathway, and p53 pathways. We also explored the possible mechanism of action for the anti-diabetic effect of berberine. Further studies are warranted to elucidate the mechanisms of action of berberine using systems biology approach.

Berberine: new perspectives for old remedies

Chemical compounds derived from plants have been used since the origin of human beings to counteract a number of diseases. Among them, the natural isoquinoline alkaloid berberine has been employed in Ayurvedic and Chinese Medicine for hundreds of years with a wide range of pharmacological and biochemical effects. More recently, a growing body of reports supports the evidence that berberine has anticancer effects, being able to block the proliferation of and to kill cancer cells. This review addresses the properties and therapeutic use of berberine and focuses on the recent advances as promising anticancer drug lead.

Berberine hydrochloride: anticancer activity and nanoparticulate delivery system

BACKGROUND

Berberine hydrochloride is a conventional component in Chinese medicine, and is characterized by a diversity of pharmacological effects. However, due to its hydrophobic properties, along with poor stability and bioavailability, the application of berberine hydrochloride was hampered for a long time. In recent years, the pharmaceutical preparation of berberine hydrochloride has improved to achieve good prospects for clinical application, especially for novel nanoparticulate delivery systems. Moreover, anticancer activity and novel mechanisms have been explored, the chance of regulating glucose and lipid metabolism in cancer cells showing more potential than ever. Therefore, it is expected that appropriate pharmaceutical procedures could be applied to the enormous potential for anticancer efficacy, to give some new insights into anticancer drug preparation in Chinese medicine.

METHODS AND RESULTS

We accessed conventional databases, such as PubMed, Scope, and Web of Science, using "berberine hydrochloride", "anti-cancer mechanism", and "nanoparticulate delivery system" as search words, then summarized the progress in research, illustrating the need to explore reprogramming of cancer cell metabolism using nanoparticulate drug delivery systems.

CONCLUSION

With increasing research on regulation of cancer cell metabolism by berberine hydrochloride and troubleshooting of issues concerning nanoparticulate delivery preparation, berberine hydrochloride is likely to become a natural component of the nanoparticulate delivery systems used for cancer therapy. Meanwhile, the known mechanisms of berberine hydrochloride, such as decreased multidrug resistance and enhanced sensitivity of chemotherapeutic drugs, along with improvement in patient quality of life, could also provide new insights into cancer cell metabolism and nanoparticulate delivery preparation.

Anti-cancer natural products isolated from chinese medicinal herbs

In recent years, a number of natural products isolated from Chinese herbs have been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, retard metastasis and enhance chemotherapy, exhibiting anti-cancer potential both in vitro and in vivo. This article summarizes recent advances in in vitro and in vivo research on the anti-cancer effects and related mechanisms of some promising natural products. These natural products are also reviewed for their therapeutic potentials, including flavonoids (gambogic acid, curcumin, wogonin and silibinin), alkaloids (berberine), terpenes (artemisinin, β-elemene, oridonin, triptolide, and ursolic acid), quinones (shikonin and emodin) and saponins (ginsenoside Rg3), which are isolated from Chinese medicinal herbs. In particular, the discovery of the new use of artemisinin derivatives as excellent anti-cancer drugs is also reviewed.

Anti-cancer natural products isolated from chinese medicinal herbs

In recent years, a number of natural products isolated from Chinese herbs have been found to inhibit proliferation, induce apoptosis, suppress angiogenesis, retard metastasis and enhance chemotherapy, exhibiting anti-cancer potential both in vitro and in vivo. This article summarizes recent advances in in vitro and in vivo research on the anti-cancer effects and related mechanisms of some promising natural products. These natural products are also reviewed for their therapeutic potentials, including flavonoids (gambogic acid, curcumin, wogonin and silibinin), alkaloids (berberine), terpenes (artemisinin, β-elemene, oridonin, triptolide, and ursolic acid), quinones (shikonin and emodin) and saponins (ginsenoside Rg₃), which are isolated from Chinese medicinal herbs. In particular, the discovery of the new use of artemisinin derivatives as excellent anti-cancer drugs is also reviewed.

Dietary administration of berberine or Phellodendron amurense extract inhibits cell cycle progression and lung tumorigenesis

Phellodendron amurense extract is a Chinese herbal remedy that has recently been studied for its antitumor, antimicrobial and other biological activities. It is previously unknown if these agents are bioavailable and effective against tumors when delivered as a dietary component. It is also unknown if the anti-tumorigenic properties of berberine, an isoquinoline alkaloid component of P. amurense, is equally effective when administered alone. There are contrasting reports on the cellular processes involved in anti-tumorigenesis by P. amurense and berberine. Here we find that berberine, when administered orally through the diet, inhibits in vivo tumorigenesis of both p53 expressing and p53 null lung tumor xenografts equally whether administered in its pure form or as a part of P. amurense extract. We also show that berberine induces G1 cell cycle arrest, inhibits proliferative kinase signaling and arrests the growth of lung tumor cells in culture. Berberine administered in the diet was detectable by HPLC in the lungs of mice fed P. amurense or equivalent doses of berberine at concentrations of 455 and 518 ng/ml respectively and inhibited the growth of xenografted A549 cell tumors, which grew to 9.4 and 6.4 mm³ respectively, compared to 58.9 mm³ in control mice (P < 0.001). Phosphorylation of Akt, CREB and MAPK was inhibited in A549 cells by P. amurense. Demonstration of oral bioavailability and anti-tumorigenic efficacy of dietary berberine, as well as further demonstration of signaling pathway modulation and cell-cycle arrest, implicate this relatively safe, natural compound as a potentially important therapeutic and chemopreventive agent for lung cancer.

A systematic review of the anticancer properties of berberine, a natural product from Chinese herbs

Natural products represent a rich reservoir of potential small chemical molecules exhibiting antiproliferation and anticancer properties. An example is berberine, a protoberberine alkaloid widely distributed in medical plants used in traditional Chinese prescriptions. Recent advances have shown that berberine exerts anticancer activities both in vitro and in vivo through different mechanisms. Berberine shows inhibitory effects on the proliferation and reproduction of certain tumorigenic microorganisms and viruses, such as Heliobacter pylori and hepatitis B virus. Transcriptional regulation of some oncogene and carcinogenesis-related gene expression and interaction with both DNA and RNA are also well documented. Besides, berberine is a broad spectrum enzyme inhibitor, which affects N-acetyltransferase, cyclooxygenase-2, and topoisomerase activities and gene/protein expression. These actions, together with the regulation of reactive oxygen species production, mitochondrial transmembrane potential, and nuclear factor-kappaB activation might underlie its antiproliferative and proapoptotic effects. More importantly, the suppression of tumor growth and metastasis, the beneficial application in combined medication, and the improvement of multidrug resistance both in vivo and in vitro clearly show its potential as an alternative medicine for tumor chemotherapy.

9-N-Substituted berberine derivatives: stabilization of G-quadruplex DNA and down-regulation of oncogene c-myc

A series of 9-N-substituted berberine derivatives (2a-j) were synthesized and evaluated as a new class of G-quadruplex binding ligands. G-quadruplex of DNA had been proven to be the transcription controller of human c-myc gene. The interaction of 9-N-substituted berberine derivatives with G-quadruplex DNA in c-myc was examined via EMSA, CD spectroscopy, FRET-melting method, PCR-stop assay, competitive dialysis, cell proliferation assay, and RT-PCR assay. The experiment results indicated that these derivatives could selectively induce and stabilize the formation of intramolecular parallel G-quadruplex in c-myc, which led to down-regulation of transcription of the c-myc in the HL60 lymphomas cell line. The related structure-activity relationships were also discussed.

Evaluation of flavonoids binding to DNA duplexes by electrospray ionization mass spectrometry

In this study, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding interactions of ten flavonoid aglycones and ten flavonoid glycosides with DNA duplexes. Relative binding affinities of the flavonoids toward DNA duplexes were estimated based on the fraction of bound DNA. The results revealed that the 4'-OH group of flavonoid aglycones was essential for their DNA-binding properties. Flavonoid glycosides with sugar chain linked on ring A or ring B showed enhanced binding toward the duplexes over their aglycone counterparts, whereas glycosylation of the flavonol quercetin on ring C exhibited a less pronounced effect. The aglycone skeletons and other hydroxyl substitutions on the aglycone also have an effect on the fractions of bound DNA. Upon collision-induced dissociation, the complexes containing flavonoid aglycones underwent the predominant ejection of a neutral ligand molecule, suggesting an intercalative DNA-binding mode. However, for complexes containing flavonoid glycosides, the loss of nucleobase increased to different extents, indicating a stronger binding or different binding mode. The results may provide not only a deeper insight into the DNA-binding properties of flavonoids but also a useful guideline for the design of efficient DNA-binding agents for chemotherapy.

Berberine-DNA complexation: new insights into the cooperative binding and energetic aspects

The equilibrium binding of the cytotoxic plant alkaloid berberine to various DNAs and energetics of the interaction have been studied. At low ratios of bound alkaloid to base pair, the binding exhibited cooperativity to natural DNAs having almost equal proportions of AT and GC sequences. In contrast, the binding was non-cooperative to DNAs with predominantly high AT or GC sequences. Among the synthetic DNAs, cooperative binding was observed with poly(dA).poly(dT) and poly(dG).poly(dC) while non-cooperative binding was seen with poly(dA-dT).poly(dA-dT) and poly(dG-dC).poly(dG-dC). Both cooperative and non-cooperative bindings were remarkably dependent on the salt concentration of the media. Linear plots of ln K(a) versus [Na(+)] for poly(dA).poly(dT) and poly(dA-dT).poly(dA-dT) showed the release of 0.56 and 0.75 sodium ions respectively per bound alkaloid. Isothermal titration calorimetry results revealed the binding to be exothermic and favoured by both enthalpy and entropy changes in all DNAs except the two AT polymers and AT rich DNA, where the same was predominantly entropy driven. Heat capacity values (DeltaCp(o)) of berberine binding to poly(dA).poly(dT), poly(dA-dT).poly(dA-dT), Clostridium perfringens and calf thymus DNA were -98, -140, -120 and -110 cal/mol K respectively. This study presents new insights into the binding dependent base pair heterogeneity in DNA conformation and the first complete thermodynamic profile of berberine binding to DNAs.

Studies on alkaloids binding to GC-rich human survivin promoter DNA using positive and negative ion electrospray ionization mass spectrometry

Electrospray ionization mass spectrometry (ESI-MS) was used to investigate the binding of 13 alkaloids to two GC-rich DNA duplexes which are critical sequences in human survivin promoter. Negative ion ESI-MS was first applied to screen the binding of the alkaloids to the duplexes. Six alkaloids (including berberine, jatrorrhizine, palmatine, reserpine, berbamine, and tetrandrine) show complexation with the target DNA sequences. Relative binding affinities were estimated from the negative ion ESI data, and the alkaloids show a binding preference to the duplex with higher GC content. Positive ion ESI mass spectra of the complexes were also recorded and compared with those obtained in negative ion mode. Only the 1 : 1 complex with berbamine was observed with lower abundance in the positive ion mass spectrum while complexes with the other alkaloids were absolutely absent. Collision-induced dissociation (CID) experiments indicate that the complexes with the protoberberine alkaloids (berberine, jatrorrhizine, and palmatine) dissociate via base loss and covalent cleavage. In contrast, product ion spectra of the complexes with the alkaloids reserpine, berbamine, and tetrandrine show the predominant loss of a neutral alkaloid molecule, accompanied by base loss and covalent cleavage to a lesser extent. A comparison of the gas-phase behaviors of complexes with the alkaloids to those with the traditional DNA binders has suggested an intercalative binding mode of these alkaloids to the target DNA duplexes.