Genotoxicity of the isoquinoline alkaloid berberine in prokaryotic and eukaryotic organisms

Studies on Activities and Chemical Characterization of Medicinal Plants in Search for New Antimalarials: A Ten Year Review on Ethnopharmacology

Malaria is an endemic disease that affected 229 million people and caused 409 thousand deaths, in 2019. Disease control is based on early diagnosis and specific treatment with antimalarial drugs since no effective vaccines are commercially available to prevent the disease. Drug chemotherapy has a strong historical link to the use of traditional plant infusions and other natural products in various cultures. The research based on such knowledge has yielded two drugs in medicine: the alkaloid quinine from Cinchona species, native in the Amazon highland rain forest in South America, and artemisinin from Artemisia annua, a species from the millenary Chinese medicine. The artemisinin-based combination therapies (ACTs), proven to be highly effective against malaria parasites, and considered as “the last bullet to fight drug-resistant malaria parasites,” have limited use now due to the emergence of multidrug resistance. In addition, the limited number of therapeutic options makes urgent the development of new antimalarial drugs. This review focuses on the antimalarial activities of 90 plant species obtained from a search using Pubmed database with keywords “antimalarials,” “plants” and “natural products.” We selected only papers published in the last 10 years (2011–2020), with a further analysis of those which were tested experimentally in malaria infected mice. Most plant species studied were from the African continent, followed by Asia and South America; their antimalarial activities were evaluated against asexual blood parasites, and only one species was evaluated for transmission blocking activity. Only a few compounds isolated from these plants were active and had their mechanisms of action delineated, thereby limiting the contribution of these medicinal plants as sources of novel antimalarial pharmacophores, which are highly necessary for the development of effective drugs. Nevertheless, the search for bioactive compounds remains as a promising strategy for the development of new antimalarials and the validation of traditional treatments against malaria. One species native in South America, Ampelozyzyphus amazonicus, and is largely used against human malaria in Brazil has a prophylactic effect, interfering with the viability of sporozoites in in vitro and in vivo experiments.

Research Progress on Antibacterial Activities and Mechanisms of Natural Alkaloids: A Review

Alkaloids are nitrogen-containing heterocyclic compounds typically isolated from plants. They represent one of the most important types of natural products because of their large number and structural diversity and complexity. Based on their chemical core structures, alkaloids are classified as isoquinolines, quinolines, indoles, piperidine alkaloids, etc. In-depth analyses of alkaloids have revealed their antibacterial activities. To date, due to the widespread use of antibiotics, the problem of drug-resistant bacterial infections has been gradually increasing, which severely affects the clinical efficacy of antibacterial therapies and patient safety. Therefore, significant research efforts are focused on alkaloids because they represent a potentially new type of natural antibiotic with a wide antibacterial spectrum, rare adverse reactions, and a low tendency to produce drug resistance. Their main antibacterial mechanisms include inhibition of bacterial cell wall synthesis, change in cell membrane permeability, inhibition of bacterial metabolism, and inhibition of nucleic acid and protein synthesis. This article reviews recent reports about the chemical structures and the antibacterial activities and mechanisms of alkaloids. The purpose is to solve the problem of bacterial resistance and to provide a certain theoretical basis and research ideas for the development of new antibacterial drugs.

In Vitro and In Vivo Biological Activity of Berberine Chloride against Uropathogenic E. coli Strains Using Galleria mellonella as a Host Model

Berberine is an alkaloid of the protoberberine type used in traditional oriental medicine. Its biological activities include documented antibacterial properties against a wide variety of microorganisms; nonetheless, its use against Escherichia coli strains isolated from urinary infections has not yet been widely investigated in vivo. The emergence of antimicrobial resistance requires new therapeutic approaches to ensure the continued effectiveness of antibiotics for the treatment and prevention of urinary infections. Moreover, uropathogenic Escherichia coli (UPEC) has developed several virulence factors and resistance to routine antibiotic therapy. To this end, several in vitro and in vivo tests were conducted to assess the activity of berberine on uropathogenic E. coli strains. Galleria mellonella as an infection model was employed to confirm the in vivo translatability of in vitro data on berberine activity and its influence on adhesion and invasion proprieties of E. coli on human bladder cells. In vitro pre-treatment with berberine was able to decrease the adhesive and invasive UPEC ability. In vivo treatment increased the larvae survival infected with UPEC strains and reduced the number of circulating pathogens in larvae hemolymph. These preliminary findings demonstrated the efficacy and reliability of G. mellonella as in vivo model for pre-clinical studies of natural substances.

Selectivity of major isoquinoline alkaloids from Chelidonium majus towards telomeric G-quadruplex: A study using a transition-FRET (t-FRET) assay

BACKGROUND

Natural bioproducts are invaluable resources in drug discovery. Isoquinoline alkaloids of Chelidonium majus constitute a structurally diverse family of natural products that are of great interest, one of them being their selectivity for human telomeric G-quadruplex structure and telomerase inhibition.

METHODS

The study focuses on the mechanism of telomerase inhibition by stabilization of telomeric G-quadruplex structures by berberine, chelerythrine, chelidonine, sanguinarine and papaverine. Telomerase activity and mRNA levels of hTERT were estimated using quantitative telomere repeat amplification protocol (q-TRAP) and qPCR, in MCF-7 cells treated with different groups of alkaloids. The selectivity of the main isoquinoline alkaloids of Chelidonium majus towards telomeric G-quadruplex forming sequences were explored using a sensitive modified thermal FRET-melting measurement in the presence of the complementary oligonucleotide CT22. We assessed and monitored G-quadruplex topologies using circular dichroism (CD) methods, and compared spectra to previously well-characterized motifs, either alone or in the presence of the alkaloids. Molecular modeling was performed to rationalize ligand binding to the G-quadruplex structure.

RESULTS

The results highlight strong inhibitory effects of chelerythrine, sanguinarine and berberine on telomerase activity, most likely through substrate sequestration. These isoquinoline alkaloids interacted strongly with telomeric sequence G-quadruplex. In comparison, chelidonine and papaverine had no significant interaction with the telomeric quadruplex, while they strongly inhibited telomerase at transcription level of hTERT. Altogether, all of the studied alkaloids showed various levels and mechanisms of telomerase inhibition.

CONCLUSIONS

We report on a comparative study of anti-telomerase activity of the isoquinoline alkaloids of Chelidonium majus. Chelerythrine was most effective in inhibiting telomerase activity by substrate sequesteration through G-quadruplex stabilization.

GENERAL SIGNIFICANCE

Understanding structural and molecular mechanisms of anti-cancer agents can help in developing new and more potent drugs with fewer side effects. Isoquinolines are the most biologically active agents from Chelidonium majus, which have shown to be telomeric G-quadruplex stabilizers and potent telomerase inhibitors.

Effects of Berberine on Cell Cycle, DNA, Reactive Oxygen Species, and Apoptosis in L929 Murine Fibroblast Cells

Berberine, an isoquinoline alkaloid isolated from several traditional Chinese herbal medicines (TCM), exhibits a strong antimicrobial activity in the treatment of diarrhea. However, it causes human as well as animal toxicity from heavy dosage. The present study was conducted to investigate the cytotoxicity of berberine and its possible trigger mechanisms resulting in cell cycle arrest, DNA damage, ROS (reactive oxygen species) level, mitochondrial membrane potential change, and cell apoptosis in L929 murine fibroblast (L929) cells. The cells were cultured in vitro and treated with different concentrations of berberine for 24 h. The results showed that cell viability was significantly decreased in a subjected dose-dependent state; berberine concentrations were higher than 0.05 mg/mL. Berberine at a concentration above 0.1 mg/mL altered the morphology of L929 cells. Cells at G2/M phase were clear that the level of ROS and cell apoptosis rates increased in 0.1 mg/mL group. Each DNA damage indicator score (DIS) increased in groups where concentration of berberine was above 0.025 mg/mL. The mitochondrial membrane potential counteractive balance mechanics were significantly altered when concentrations of berberine were above 0.005 mg/mL. In all, the present study suggested that berberine at high dosage exhibited cytotoxicity on L929 which was related to resultant: cell cycle arrest; DNA damage; accumulation of intracellular ROS; reduction of mitochondrial membrane potential; and cell apoptosis.

Assessment of the embryotoxicity of four Chinese herbal extracts using the embryonic stem cell test

Rhizoma Atractylodes macrocephala, Radix Isatidis, Coptis chinensis and Flos Genkwa are common herbal remedies used by pregnant woman in China. In this study, their potential embryotoxicity was assessed using the embryonic stem cell test (EST) and a prediction model. The potential embryotoxicity of the herbs was based on three endpoints: the concentrations of the compounds that inhibited the proliferation of 50% of embryonic stem cells (ESCs) (IC50ES), the concentrations that inhibited 50% of 3T3 cells (IC503T3), and the concentrations that inhibited the differentiation of 50% of ESCs (ID50ES). The results revealed that Rhizoma Atractylodes macrocephala and Radix Isatidis are non-embryotoxic compounds. Coptis chinensis extracts appeared to demonstrated weak embryotoxicity, and Flos Genkwa exhibited strong embryotoxicity. These results may be useful in guiding the clinical use of these herbs and in expanding the application of the EST to the field of traditional Chinese medicine.

Berberine induces apoptosis and DNA damage in MG‑63 human osteosarcoma cells

Berberine, an isoquinoline alkaloid extracted from the dry root of Coptidis Rhizoma, has been found to exhibit marked anticancer effects on a panel of established cancer cells. Among the human osteosarcoma lines treated, MG-63 cells were found to be the most sensitive. The present study investigated the potential genotoxic effect of berberine on MG-63 human osteosarcoma cells. The effect of berberine on cell viability was determined using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay and cell apoptosis was analyzed by flow cytometry and a DNA ladder assay. γH2AX focus formation was used to detect DNA damage in MG-63 cells. Berberine induced a significant increase in apoptosis in MG-63 cells in a concentration- and time-dependent manner, as determined by DNA fragmentation analysis and flow cytometry. Furthermore, berberine induced significant concentration- and time-dependent increases in DNA damage compared with that in the negative control. In conclusion, these observations indicated that berberine induced apoptosis and DNA damage in MG-63 cells.

Safety evaluation of main alkaloids from Rhizoma Coptidis

ETHNOPHARMACOLOGICAL RELEVANCE

Rhizoma Coptidis (RC), a widely used traditional Chinese medicine, has been used for the treatment of heat-clearing and detoxifying, but there is very little information on its safety.

AIM OF THE STUDY

To provide information on the safety of RC, we evaluated the toxicity of the crude RC and RC alkaloids (berberine, coptisine, palmatine and epiberberine) including cytotoxicity, acute toxicity in mice and sub-chronic toxicity in rats.

MATERIALS AND METHODS

The cytotoxicity of RC alkaloids was tested in HepG2 and 3T3-L1 cells by the MTT assay. The acute toxicity of RC alkaloids was tested in mice and the mortality was calculated at the end of experiment. For sub-chronic toxicity study, the rats were treated with the RC alkaloids at a dose of 156 mg/kg/day and RC at a dose of 521 mg/kg/day for 90 days. Mortality, clinical signs, body weight changes, organ weights, urinalysis and hematological parameters, gross necropsy and histopathology were monitored during the study period.

RESULTS

The cell assay indicates that the IC(50) values of berberine, coptisine, palmatine and epiberberine in HepG2 cells were 48.17, 64.81, 112.80 and 120.58 μg/mL, which in 3T3-L1 cells were 41.76, 56.48, 84.32 and 104.18 μg/mL, respectively. In the acute toxicity assay, the LD(50) values of four alkaloids were 713.57, 852.12, 1533.68 and 1360 mg/kg, respectively. However, in the sub-chronic toxicity study, no mortality and morbidity were observed which could be related to RC alkaloids and RC treatment. Besides, there was no abnormality in clinical signs, body weights, organ weights, urinalysis, hematological parameters, gross necropsy and histopathology in any of the animals after the oral administration of RC alkaloids and RC.

CONCLUSIONS

Taking these results together, we came to the conclusion that the toxicity of berberine is the maximum and palmatine is the minimal in four RC alkaloids. The currently recommended doses of RC alkaloids and RC consumed are relatively safe.

Genetic evidence for inhibition of bacterial division protein FtsZ by berberine

Background

Berberine is a plant alkaloid that is widely used as an anti-infective in traditional medicine. Escherichia coli exposed to berberine form filaments, suggesting an antibacterial mechanism that involves inhibition of cell division. Berberine is a DNA ligand and may induce filamentation through induction of the SOS response. Also, there is biochemical evidence for berberine inhibition of the cell division protein FtsZ. Here we aimed to assess possible berberine mechanism(s) of action in growing bacteria using genetics tools.

Methodology/Principal Findings

First, we tested whether berberine inhibits bacterial growth through DNA damage and induction of the SOS response. The SOS response induced by berberine was much lower compared to that induced by mitomycin C in an SOS response reporter strain. Also, cell filamentation was observed in an SOS-negative E. coli strain. To test whether berberine inhibits FtsZ, we assessed its effects on formation of the cell division Z-rings, and observed a dramatic reduction in Z-rings in the presence of berberine. We next used two different strategies for RNA silencing of ftsZ and both resulted in sensitisation of bacteria to berberine, visible as a drop in the Minimum Inhibitory Concentration (MIC). Furthermore, Fractional Inhibitory Concentration Indices (FICIs) showed a high level of synergy between ftsZ silencing and berberine treatment (FICI values of 0.23 and 0.25 for peptide nucleic acid- and expressed antisense RNA-based silencing of ftsZ, respectively). Finally, over-expression of ftsZ led to a mild rescue effect in berberine-treated cells.

Conclusions

The results argue against DNA binding as the primary mechanism of action of berberine and support the hypothesis that its antibacterial properties are due to inhibition of the cell division protein FtsZ. In addition, the genetic approach used here provides a means to rapidly test the activity of other putative FtsZ inhibitors.

Evaluation of 5-aminoisoquinoline (5-AIQ), a novel PARP-1 inhibitor for genotoxicity potential in vitro and in vivo

5-aminoisoquinoline (5-AIQ) is an active PARP-1 inhibitor as well as an important functional group various drugs. Quinolines are generally known as mutagenic and carcinogenic in various in vitro and in vivo systems, while both positive and negative findings are available on the mutagenic potential of several isoquinolines. Since no literature is available on the genotoxicity of 5-AIQ, a battery of tests were conducted, in accordance with relevant OECD protocols, such as bacterial reverse mutation test, in vitro chromosomal aberration test, and bone marrow micronucleus test in mouse. These studies demonstrate that 5-AIQ does not possess genotoxic activity both with in vitro and in vivo systems. The findings substantiate the therapeutic value of 5-AIQ.

Berberine reduces the hypoxic-ischemic insult in rat pup brain

Berberine, an isoquinoline alkaloid extracted from medicinal herbs, has been used as antipyretic, antidiarrheal, bactericide and anti-inflammatory agent. In this study, berberine effects on neuronal damage have been examined. The right carotid artery of seven-day-old rat pups was ligated (ischemic insult), then berberine solution (0.2, 0.5, 1 or 2 mg/kg) was injected intra-peritoneally, and 30 minutes later pups were passed through hypoxic condition with breathing in air containing 10% oxygen and 90% nitrogen(hypoxic insult). The day after that the brains of pups were enucleated for pathologic assessment. Pathologic review of the samples obtained from rats treated with different doses of berberine in comparison with samples from pups treated by normal saline showed that there was a significant reduction of brain injury and edema in the rats treated with berberine. Our study also demonstrates that berberine reduces brain ischemic-hypoxic injury dose-dependently. Therefore, beberine may be considered as useful anti-stroke agent.

Berberine induces p53-dependent cell cycle arrest and apoptosis of human osteosarcoma cells by inflicting DNA damage

Alkaloid berberine is widely used for the treatment of diarrhea and other diseases. Many laboratory studies showed that it exhibits anti-proliferative activity against a wide spectrum of cancer cells in culture. In this report we studied the mechanisms underlying the inhibitory effects of berberine on human osteosarcoma cells and on normal osteoblasts. The inhibition was largely attributed to cell cycle arrest at G1 and G2/M, and to a less extent, to apoptosis. The G1 arrest was dependent on p53, as G1 arrest was abolished in p53-deficient osteosarcoma cells. The induction of G1 arrest and apoptosis was accompanied by a p53-dependent up-regulation of p21 and pro-apoptotic genes. However, the G2/M arrest could be induced by berberine regardless of the status of p53. Interestingly, DNA double-strand breaks, as measured by the phosphorylation of H2AX, were remarkably accumulated in berberine-treated cells in a dose-dependent manner. Thus, one major mechanism by which berberine exerts its growth-inhibitory effect is to inflict genomic lesions on cells, which in turn trigger the activation of p53 and the p53-dependent cellular responses including cell cycle arrest and apoptosis.

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.

Berberine targets assembly of Escherichia coli cell division protein FtsZ

The ever increasing problem of antibiotic resistance necessitates a search for new drug molecules that would target novel proteins in the prokaryotic system. FtsZ is one such target protein involved in the bacterial cell division machinery. In this study, we have shown that berberine, a natural plant alkaloid, targets Escherichia coli FtsZ, inhibits the assembly kinetics of the Z-ring, and perturbs cytokinesis. It also destabilizes FtsZ protofilaments and inhibits the FtsZ GTPase activity. Saturation transfer difference NMR spectroscopy of the FtsZ-berberine complex revealed that the dimethoxy groups, isoquinoline nucleus, and benzodioxolo ring of berberine are intimately involved in the interaction with FtsZ. Berberine perturbs the Z-ring morphology by disturbing its typical midcell localization and reduces the frequency of Z-rings per unit cell length to half. Berberine binds FtsZ with high affinity ( K D approximately 0.023 microM) and displaces bis-ANS, suggesting that it may bind FtsZ in a hydrophobic pocket. Isothermal titration calorimetry suggests that the FtsZ-berberine interaction occurs spontaneously and is enthalpy/entropy-driven. In silico molecular modeling suggests that the rearrangement of the side chains of the hydrophobic residues in the GTP binding pocket may facilitate the binding of the berberine to FtsZ and lead to inhibition of the association between FtsZ monomers. Together, these results clearly indicate the inhibitory role of berberine on the assembly function of FtsZ, establishing it as a novel FtsZ inhibitor that halts the first stage in bacterial cell division.

Molecular aspects on the interaction of protoberberine, benzophenanthridine, and aristolochia group of alkaloids with nucleic acid structures and biological perspectives

Alkaloids occupy an important position in chemistry and pharmacology. Among the various alkaloids, berberine and coralyne of the protoberberine group, sanguinarine of the benzophenanthridine group, and aristololactam-beta-d-glucoside of the aristolochia group have potential to form molecular complexes with nucleic acid structures and have attracted recent attention for their prospective clinical and pharmacological utility. This review highlights (i) the physicochemical properties of these alkaloids under various environmental conditions, (ii) the structure and functional aspects of various forms of deoxyribonucleic acid (DNA) (B-form, Z-form, H(L)-form, protonated form, and triple helical form) and ribonucleic acid (RNA) (A-form, protonated form, and triple helical form), and (iii) the interaction of these alkaloids with various polymorphic DNA and RNA structures reported by several research groups employing various analytical techniques like absorbance, fluorescence, circular dichroism, and NMR spectroscopy; electrospray ionization mass spectrometry, thermal melting, viscosity, and DNase footprinting as well as molecular modeling and thermodynamic studies to provide detailed binding mechanism at the molecular level for structure-activity relationship. Nucleic acids binding properties of these alkaloids are interpreted in relation to their biological activity.

Mutagenic and antioxidant activities of Croton lechleri sap in biological systems

The sap of Croton lechleri Muell.-Arg (Euphorbiaceae), called Dragon's blood, is used in folk medicine as a cicatrizant, anti-inflammatory and to treat cancer. In this research, the antioxidant activity of Croton lechleri sap was evaluated against the yeast Saccharomyces cerevisiae and against maize plantlets treated with the oxidative agents apomorphine and hydrogen peroxide. The mutagenic activity of the sap was also analyzed using the Salmonella/microsome assay (Salmonella typhimurium TA97a, TA98, TA100, TA102, TA1535) and in cells of the yeast Saccharomyces cerevisiae. The results showed that Croton lechleri sap possesses significant antioxidant activity against the oxidative damages induced by apomorphine in Saccharomyces cerevisiae under all the conditions studied. However, in the case of hydrogen peroxide, antioxidant activity of the sap was detected only in cells in the stationary phase of growth. The sap was also able to protect cells of the maize plantlets from the toxic effect of apomorphine. This sap showed mutagenic activity for strain TA1535 of Salmonella typhimurium in the presence of metabolic activation and a weak mutagenic activity for strain TA98. These strains detect base pair substitutions and frameshift mutations, respectively. Mutagenicity was also observed in a haploid Saccharomyces cerevisiae strain XV185-14c for the lys1-1, his1-7 locus-specific reversion and hom3-10 frameshift mutations.

Genotoxic and recombinogenic activities of the two beta-carboline alkaloids harman and harmine in Saccharomyces cerevisiae

The cytotoxical beta-carboline alkaloids harman and harmine occur in medical plants and in a variety of foods, alcoholic beverages, and industrial waste. We applied them to the yeast Saccharomyces cerevisiae to test for putative genotoxicity, mutagenicity and recombinogenicity and to determine whether harman and harmine produced repairable DNA damage. Harmine was more cytotoxic than harman for exponentially growing haploid and diploid cells. Only harmine-induced crossing-over and mitotic gene conversion but both alkaloids were frameshift mutagens in yeast. Mutants defective in excision-resynthesis repair (rad3 and rad1), in error-prone repair (rad6) and in recombinational repair (rad52) showed enhanced sensitivity to harmine and harman, but the ranking of sensitivities was different for the two alkaloids. It appears that both alkaloids are probably capable of inducing DNA single and/or double strand breaks. An epistatic interaction was shown between rad3-e5 and rad52-1 mutants alleles, indicating that excision-resynthesis and strand-break repair may have common steps in the repair of DNA damage induced by these alkaloids. The non-epistatic interaction observed in rad1Delta rad6Delta double mutants indicated that both excision-resynthesis and error-prone repair are independently involved in repair of harman- and harmine-induced DNA lesions.

Dose finding in the Ames Salmonella assay

Threshold dose/concentration values, such as the lowest effective dose, minimum effective dose or the lowest effective concentration (LED, MED or LEC, respectively) are in use as an alternative to the mutagen potency measures based on the 'rate' measurements (e.g., the slope of the initial part of the dose-response curve). In this respect, several statistical procedures for the corresponding so-called 'dose finding' were proposed during the last decades. However, most of them disregard the discrete nature of responses such as the plate colony count in the Ames Salmonella assay. When the plate counts agree with the Poisson assumption, two procedures considered here seem to be appropriate for the dose finding. One is based on the stepwise collapsing of the homogeneous control and dose counts; another consists of constructing the confidence limits for the mutation induction factor (MIF). When the dose and control counts are non-overlapping, the simple 'visual' non-parametric estimation of LED is possible. Applicability and validity of the methods is demonstrated with the two data sets on the mutagenicity of the beta-carboline alkaloid, harmine, and one of the oxidation products of apomorphine.

Detection of DNA in agarose gels using berberine and Mordant Yellow 3R

A nontoxic and simple staining method for the detection of DNA in agarose gels is described. After eletrophoretic separation, the gels were stained with 5 microg/ml of berberine (BB) prepared in distilled water and then the gels were soaked in 20 microg/ml of aqueous Mordant Yellow 3R (MY3R) solution. Employment of MY3R as a counterion dye efficiently quenched unwanted background fluorescence of BB. This method can detect as little as 10 ng of plasma membrane H(+)-ATPase cDNA obtained from Arabidopsis thaliana L. (AHA1, 3.2 kb) under a long wavelength of UV irradiation (366 nm) within 1 h.

Inhibition of in-vitro lymphocyte transformation by the isoquinoline alkaloid berberine

Berberine is an isoquinoline alkaloid with multiple pharmacological actions, including an anti-inflammatory activity. The effects of berberine on in-vitro cellular proliferation of human peripheral lymphocytes stimulated with phytohaemagglutinin, concanavalin A and pokeweed mitogen were studied. Mononuclear cells were cultured in flat-bottomed 96-well microplates at 37 degrees C for 96-144 h in the presence of one mitogen at different concentrations and the alkaloid at doses of 2.5 to 20 microg mL-1. The mitogen-induced response of lymphocytes was evaluated from the extent of the incorporation of [3H]thymidine into cells in-vitro. A consistent and progressive inhibitory influence of berberine with increasing concentrations in culture was identified with all mitogens and was more pronounced with pokeweed mitogen. The effect of berberine was observed in phytohaemagglutinin (PHA)-and concanavalin A-activated lymphocytes when the drug was added during the first 24 h of culture, whereas the same effect occurred throughout the incubation period in pokeweed mitogen-stimulated cells. The viability of lymphocytes following treatment with the drug, as assessed by the trypan blue exclusion test, revealed no change when compared with the same untreated lymphocytes, indicating no lymphocytotoxic activity. We conclude that some effects of berberine, especially its anti-inflammatory action, may arise in part from the inhibition of DNA-synthesis in activated lymphocytes.