Serum starvation is as efficient as roscovitine on the cycle synchronization in G0/G1 of red-rumped agouti fibroblasts

Fibroblast cycle synchronization in G0/G1 is an essential step for nuclear reprogramming by cloning or induced cells to pluripotency. Considering the diversity among rodents and the ecological and scientific importance of these animals, we compared the contact inhibition, serum starvation, and 10 µM of roscovitine as methods of synchronization of red-rumped agouti fibroblasts. The effects of each protocol were evaluated on the percentage of cycle phase, morphology, viability, and apoptosis levels. The results showed that culturing the cells to serum starvation for 24 h (75.9%), 48 h (81.6%), 72 h (86.2%), 96 h (84.0%), and 120 h (83.7%) yielded a significantly higher percentage of cells arrested in the G0/G1 (P < 0.05) phase than cells not subjected to any cell cycle synchronization method (31.4%). Also, this effect was not different between the times of 48 and 120 h (P > 0.05). A similar response was observed for cells cultured with roscovitine for 12 h (86.9%), 24 h (74.8%), and 48 h (81.7%), with a higher percentage of synchronized cells in G0/G1 compared to cells not submitted to any synchronization treatment (52.2%). Nevertheless, this effect was best evidenced at 12 h (P < 0.05). Also, the contact inhibition for 24-120 h could not synchronize cells in G0/G1, with values ranging from 70.9 to 77.9% (P > 0.05). Moreover, no difference was observed for morphology, viability, and apoptosis levels in any synchronization method (P > 0.05). Therefore, serum starvation is as efficient as roscovitine on cycle synchronization in G0/G1 of red-rumped agouti fibroblasts.

Hellebrigenin triggers death of promyelocytic leukemia cells by non-genotoxic ways

Bufadienolides are digitalis-like aglycones mainly found in skin secretions of toads. Among their biological properties, the mechanisms of antiproliferative action on tumor cells remain unclear for many compounds, including against leukemia cells. Herein, it was evaluated the mechanisms involved in the antiproliferative and genotoxic actions of hellebrigenin on tumor cell lines and in silico capacity to inhibit the human topoisomerase IIa enzyme. Firstly, its cytotoxic action was investigated by colorimetric assays in human tumor and peripheral blood mononuclear cells (PBMC). Next, biochemical and morphological studies were detailed by light microscopy (trypan blue dye exclusion), immunocytochemistry (BrdU uptake), flow cytometry and DNA/chromosomal damages (Cometa and aberrations). Finally, computational modelling was used to search for topoisomerase inhibition. Hellebrigenin reduced proliferation, BrdU incorporation, viability, and membrane integrity of HL-60 leukemia cells. Additionally, it increased G2/M arrest, internucleosomal DNA fragmentation, mitochondrial depolarization, and phosphatidylserine externalization in a concentration-dependent manner. In contrast to doxorubicin, hellebrigenin did not cause DNA strand breaks in HL-60 cell line and lymphocytes, and it interacts with ATPase domain residues of human topoisomerase IIa, generating a complex of hydrophobic and van der Waals interactions and hydrogen bonds. So, hellebrigenin presented potent anti-leukemic activity at concentrations as low as 0.06 μM, a value comparable to the clinical anticancer agent doxorubicin, and caused biochemical changes suggestive of apoptosis without genotoxic/clastogenic-related action, but it probably triggers catalytic inhibition of topoisomerase II. These findings also emphasize toad steroid toxins as promising lead antineoplasic compounds with relatively low cytotoxic action on human normal cells.

Cordia oncocalyx and oncocalyxones: From the phytochemistry to the anticancer action and therapeutic benefits against chronic diseases

Cordia oncocalyx Allemão is an endemic economically underexploited plant from Brazilian semi-arid region. Herein, we carried out a well-defined bibliographic review about the pharmacological activities of oncocalyxones from C. oncocalyx and mechanisms responsible for the biomedical properties. MeSH terms were used in the scientific databases for a narrative exploration. Technological development and bioproducts were also examined. Cordia oncocalyx is a deciduous tree of sexual reproduction rich in terpenoid quinones. Among them, oncocalyxone A, a 1,4-benzoquinone, the main compound from heartwood ethanol extracts, revealed anti-inflammatory and anti-edematogenic actions induced by carrageenan and dextran and antinociceptive potential in mice provoked by acetic acid and formalin. Oncocalyxone A inhibits platelet aggregation via activation of the soluble guanylate cyclase enzyme and blocks glycation processes. In addition to the antimicrobial effects against protozoa, fungi and bacteria and relaxation of smooth muscles, oncocalyxone A reduces mean blood pressure and glycemia in diabetic rats, decreases glomerular filtration parameters and tubular transport of electrolytes, and presents in vitro antimitotic and cytotoxic action upon different types of cancers, including resistant lung carcinoma lines. It has low oral acute toxicity (LD50 > 2000 mg/kg) and activates cellular apoptosis through the production of free radicals and interactions with DNA. However, no patents were found, which also emphasizes that Brazil, as the cradle of the main articles on C. oncocalyx, is wasting time and money. Moreover, slight systemic deleterious effects in mammals stimulate the use of oncocalyxone A and related compounds as lead constituents of safer drugs against chronic diseases.

Toxic profile of marinobufagin from poisonous Amazon toads and antitumoral effects on human colorectal carcinomas

ETHNOPHARMACOLOGICAL RELEVANCE

South Americans natives have extensively used the toad "kururu" to reduce/treat skin infections, cutaneous lesions and sores. They release secretions rich in bufadienolides, polyhydroxy steroids with well-documented cardiotonic and antiproliferative actions, but in vivo antitumoral evaluations in mammals are rare, and toxicological safety has been left in second place.

AIMS OF THE STUDY

This investigation used in silico, in vitro and in vivo tools to evaluate acute and subacute toxic effects of marinobufagin and the anticancer action in tumor-bearing mice models.

MATERIALS AND METHODS

Initially, in silico toxic predictions were performed, followed by in vitro assays using human and murine normal and tumor lines. Next, acute and subacute studies on mice investigated the behavior, hematological and intestinal transit profile and antitumoral activity of marinobufagin in sarcoma 180- and HCT-116 colorectal carcinoma-transplanted mice for 7 and 15 days, respectively. Ex vivo and in vivo cytogenetic assays in Sarcoma 180 and bone marrow cells and histopathological examinations were also executed.

RESULTS

In silico studies revealed ecotoxicological effects on crustaceans (Daphnia sp.), fishes (Pimephales promelas and Oryzias latipes), and algae. A 24-h marinobufagin-induced acute toxicity included signals of central activity, mainly (vocal frenzy, absence of body tonus, increased ventilation, ataxia, and equilibrium loss), and convulsions and death at 10 mg/kg. The bufadienolide presented effective in vitro cytotoxic action on human lines of colorectal carcinomas in a similar way to ouabain and tumor reduction in marinobufagin-treated SCID-bearing HCT-116 heterotopic xenografts. Animals under subacute nonlethal doses exhibited a decrease in creatinine clearance with normal levels of blood urea, probably as a result of a marinobufagin-induced renal perfusion fall. Nevertheless, only minor morphological side effects were identified in kidneys, livers, hearts and lungs.

CONCLUSIONS

Marinobufagin has in vitro and in vivo anticancer action on colorectal carcinoma and mild and reversible alterations in key metabolic organs without direct chemotherapy-induced gastrointestinal effects at subacute exposure, but it causes acute ataxia, equilibrium loss, convulsions and death at higher acute exposure.

METABOLIC PROFILING AND CYTOTOXIC ACTIVITY OF METHANOL EXTRACTS FROM Chamaecrista duckeana (P. BEZERRA & A. FERN.) H. S. IRWIN & BARNEBY (LEGUMINOSAE, CAESALPINIOIDEAE)

The genus Chamaecrista comprises more than 330 species, with only a few studies on their chemical composition and biologic activities. In this study, the phytochemical profile of leaf, stems, and fruits extracts of the C. duckeana were examined by UPLC-ESI-HRMS analysis to determine possibly bioactive constituents. The antioxidant activity was carried out through in vitro assay, by the sequestration of the free radical DPPH. To evaluate the cytotoxic activity of the extracts, an MTT assay was used and the IC50 was determined against HL60 and RAJI cell lines. The metabolic profiles of the botanical parts are dominated by flavonoid class, highlighting isoflavonoids such as daidzin and ononin. All these compounds are reported for the first time in C. duckeana. The extracts presented antioxidant potential, and the activity of the stems extract was higher than the standard butylated hydroxytoluene. In the cytotoxic assay, only HL60 line (leukemia) had growth inhibition over 80%. The stems presented more expressive cytotoxicity with IC50 of 137.3 (104.6-180.1) and 106.8 (96.52-118.3) μmol. L-1 for HL60 and RAJI, respectively. In conclusion, the present work provides an in-depth knowledge about the chemical profile of C. duckeana, a species rich in bioactive secondary metabolites with cytotoxic activity

Cytotoxicity potential of chemical constituents isolated and derivatised from Rhinella marina venom

Chemical compounds from skin secretions from toads of Bufonidae family have been long-studied. In the search for new molecules with pharmacological action, the 3β-OH groups of bufadienolides are commonly derivatised using acetyl groups. This work described the isolation and/or structural elucidation of isolated and derivatised compounds from the venom of the Brazilian anuran Rhinella marina, and their evaluation in in vitro assays. In the methanolic extract of the R. marina venom, compound cholesterol (1) was isolated from the CRV-52 fraction by classic column chromatography, dehydrobufotenine (2) by Sephadex LH-20 from the CRV-28 fraction, and a mix of suberoyl arginine (3) and compound 2 was obtained from the CRV-6-33 fraction. The compounds marinobufagin (4), telocionbufagin (5) and bufalin (6) were isolated by classic column chromatography, followed by separation via HPLC in the CRV-70 fraction, and the compound marinobufotoxin (9) was isolated by classic column chromatography in the CRV-6 fraction, here being isolated for the first time in R. marina specimens. Compounds 4 and 5 were submitted for acetylation with acetic anhydride, in the presence of pyridine and 4-dimethyilaminopiridine (DMAP), in order to obtain the compounds 3-acetyl-marinobufagin (7) and 3-acetyl-telocinobufogin (8). The isolated and derivatised compounds were identified by ¹H and ¹³C NMR, and their molecular mass confirmed by mass spectrometry. All compounds (except 1 and 3) were tested in cytotoxic assays by the MTT method and presented cytotoxic potential against human cancer cell lines, as well as against non-tumoral human embryonic kidney HEK-293 cells. With the exception of compound 2, all molecules presented IC₅₀ values < 4 μM, and none caused hemolysis of human erythrocytes, demonstrating a promising cytotoxic potential of natural and chemically-modified bufadienolides. This study presents a detailed contribution of bioactive chemicals from Brazilian Amazon Rhinella species, and indicates promising areas for further studies and pharmaceutical investments.

Cellular and biochemical antileukemic mechanisms of the meroterpenoid Oncocalyxone A

Oncocalyxone A, a 1,4-benzoquinone derived from Cordia oncocalyx, exhibits anti-inflammatory, antimicrobial and antidiabetic properties. The aim of this study was to (1) examine the cytotoxic actions of oncocalyxone A on human normal and tumor cell lines and (2) determine mechanistic actions underlying effects upon leukemia cells using cellular and molecular techniques. Antiproliferative studies on cancer cell lines, peripheral blood mononuclear cells, and human erythrocytes were performed using colorimetric assays. To understand cytotoxicity, assessments were performed with HL-60 leukemia cells (8, 16.5, or 33 µM) after 24 hr incubation using light and fluorescence microscopy, trypan blue, flow cytometry, Comet assay, western blot of caspases and poly-ADP-ribose polymerase (PARP), and effects on topoisomerase I and II. Oncocalyxone A exhibited cytotoxic action upon HL-60 cells and dividing leukocytes, but minimal hemolytic action on erythrocytes. Mechanistic investigations demonstrated reduction of cell viability, loss of membrane integrity, cell shrinking, chromatin condensation, blebbings, externalization of phosphatidylserine, caspase activation, PARP cleavage, mitochondrial depolarization, and DNA damage. Pre-treatment with N-acetylcysteine 4 mM significantly reduced DNA damage and prevented membrane integrity loss. Oncocalyxone A displayed free radical dependent antileukemic activity via apoptotic pathways and induced DNA damage in HL-60 cells. Oncocalyxone A possesses structural chemical simplicity enabling it to be a cost-effective alternative. These properties justify further improvements to enhance activity and selectivity and the development of pharmaceutical formulations. Abbreviations Acridine orange, AO; ANOVA, analysis of variance; BSA, bovine serum albumin; DI, Damage Index; DMSO, dimethylsulfoxide; EC₅₀, effective concentration 50%; EDTA, ethylenediamine tetraacetic acid; EB, ethidium bromide; HCT-116, colon carcinoma line; HL-60, promyelocytic leukemia line; IC₅₀, inhibitory concentration 50%; MTT, 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide; OVCAR-8, ovarian carcinoma line; NAC, N-acetylcysteine, PBMC, peripheral blood mononuclear cells; PBS, phosphate-buffered saline; PI, propidium iodide; PARP, poly-ADP-ribose polymerase; RPMI-1640, Roswell Park Memorial Institute medium; SF-295, glioblastoma line; ROS, reactive oxygen species; 7-AAD, 7-amino-actinomycin D; H₂-DCF-DA, 7'-dichlorodihydrofluorescein diacetate.

Chemical Constituents and Cytotoxic Activity of Rhinella jimi (Anura: Bufonidae)

Rhinella jimi toads (Stevaux, 2002) belong to the Bufonidae family, are endemic in the Brazilian Northeast and are commonly found during rainy periods. In general, amphibians of this family have in their poisons different metabolites that show a diversity of pharmacological activities. The isolation and identification of these compounds are of great importance, and techniques such as high-performance liquid chromatography coupled to mass spectrometry are widely used for the discovery of novel and known compounds in these poisons. For R. jimi poison, the ethyl acetate and methanolic extracts were obtained and thirty compounds were identified by combining ultra-performance liquid chromatography coupled to mass spectrometry (UPLC-MS) with direct infusion atmospheric pressure chemical ionization mass spectrometry (DI-APCI-MS/MS) and direct infusion electrospray mass spectrometry (DI-ESI-MS/MS) for each extract, respectively. Marinobufagin (2) and marinobufotoxin (19) were the majorities of each extract, respectively. In addition, other bufadienolides mainly present in the ethyl acetate extract, such other bufotoxins, alkaloids and arginine diacid derivatives were identified in the methanol extract. In a cytotoxic assay by 3-(4,5-dimethylthiazol-2-yl)-2,5‑diphenyltetrazolium bromide (MTT), the extracts and compound 2 demonstrated half-maximal inhibitory concentration (IC50) values better than the positive control doxorubicin, evidencing excellent cytotoxic. This is the most complete study of the chemical composition of R. jimi toad poison and its respective cytotoxic activity, promoting the enrichment of knowledge about this family and species.

New 5-carba-pterocarpans: Synthesis and preliminary antiproliferative activity on a panel of human cancer cells

Natural pterocarpans and synthetic 5-carba-pterocarpans are isosteres in which the oxygen atom at position 5 in the pyran-ring of pterocarpans is replaced by a methylene group. These 5-carba-analogues were obtained in good yields through the palladium-catalyzed oxyarylation of alcoxy-1,2-dihydronaphthalens with o-iodophenols in PEG-400. They were evaluated on human cancer cell lineages derived respectively from prostate tumor (PC3, IC₅₀ = 11.84 μmol L^-1, SI > 12)) and acute myeloid leukemia (HL-60, IC₅₀ = 8.81 μmol L^-1, SI > 16), highly incident cancer types presenting resistance against traditional chemotherapeutics. Compound 6c (LQB-492) was the most potent (IC₅₀ = 3.85 μmol L^-1, SI > 37) in SF-295 cell lineage (glioblastoma). Such findings suggest that 5-carba-pterocarpan can potentially be new hit compounds for further development of novel antiproliferative agents.

Preparation, Spectral Characterization and Anticancer Potential of Cinnamic Esters

Cinnamic acid and its derivatives show a remarkable variety of biological activities and are often studied in search of the development of new and highly effective drugs. This work aims to synthesize, characterize and evaluate the cytotoxic activity of esters derived from cinnamic acid. Eighteen esters were synthesized through Steglich’s esterification, of which eleven were not reported in the literature. All compounds were fully characterized by Fourier transform infrared epectroscopy (FTIR), nuclear magnetic resonance (1H and 13C NMR) and high-resolution mass spectrometry (HRMS) data. The cytotoxic activity of esters obtained was evaluated using four human tumor cell lines: SNB-19 (astrocytoma), HCT-116 (colon carcinoma, human), PC3 (prostate) and HL60 (promyelocytic leukemia) through the 3-(4,5-dimethyl-2-thiazolyl)- 2,5‑diphenyl-2H‑tetrazolium (MTT) colorimetric assay. These studies showed that the compound 3-methoxybenzyl (E)‑3‑(4‑methoxyphenyl)acrylate (12) is the most potent against HCT-116, PC3 and SBN-19 cells, with the lowest half maximal inhibitory concentration (IC50) value of 16.2 μM in the HCT-116 strain. The derivatives were obtained in good yields (76.6-95%), except for compounds 5-isopropyl-2-methylphenyl (E)-3-(3-hydroxy-4-methoxyphenyl)acrylate (17) (18.6%) and 2-isopropyl-5-methylphenyl (E)-3-(3-hydroxy-4-methoxyphenyl)acrylate (18) (15.5%).

Antiproliferative and photoprotective activities of the extracts and compounds from Calea fruticosa

In this paper, we complement our previous study on the antiproliferative activity of Calea fruticosa (Asteraceae) by isolating the compounds apigenin-4',7-dimethyl ether (1), budlein A (2), quercetin (3), and cichoriin (4) from the plant’s aerial parts. The antiproliferative activity of these compounds was evaluated by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method against human tumor cell lines. Compound 3 displayed moderate antiproliferative activity in three cell lines (HCT-116, PC-3, and SF-295, with cell growth inhibition values of 72.97, 74.55, and 68.94%) and high antiproliferative activity (90.86%) in the HL-60 cell line. The in vitro sun protection factor (SPF) of the extracts and compound 4, with and without sunscreen, was determined by a spectrophotometric method. The ethanol extract exhibited the highest SPF (9.67) at a concentration of 0.100 mg/mL, while compound 4, isolated from this extract, showed a SPF of 13.79 at the same concentration. A relative increased efficacy of SPF was observed for the extracts and compound 4 when sunscreen was also used. Compound 4 has not been reported previously from any species within the genus Calea. Compounds 1–4 were obtained from this species for the first time.

Pharmacological and physicochemical profile of arylacetamides as tools against human cancers

Arylacetamides are widely used as synthetic intermediates to obtain medicinal substances. This work evaluated in vitro antiproliferative activity of ten 2-Chloro-N-arylacetamides on human normal and cancer cells and detailed in vivo toxicological and anticancer investigations. Initially, cytotoxic colorimetric assays were performed using tumor lines, peripheral blood mononuclear cells (PBMC) and erythrocytes. Compounds 2, 3 and 4 were tested for acute toxicity (50, 150 and 300 mg/kg) and for subacute antitumoral capacity in HCT-116 colon carcinoma-bearing xenograft mice for 15 days at 25 mg/kg/day. Most compounds revealed cytotoxic action on tumor lines and PBMC, but activity on human erythrocytes were not detected. Molecular dipole moment, lipophilicity and electronic constant of aryl substituents had effects upon in vitro antiproliferative capacity. More common in vivo acute behavioral signals with compounds 2, 3 and 4 were muscle relaxation, reduction of spontaneous locomotor activity and number of entries in closed arms and increased number of falls andtime spent in open arms, suggesting diazepam-like anxiolytic properties. Decrease of grabbing strength and overall activity were common, but palpebral ptosis and deaths occurred at 300 mg/kg only. Compounds 2 and 3 reduced colon carcinoma growth (21.2 and 27.5%, respectively, p < 0.05) without causing apparent signals of organ-specific toxicity after subacute exposure. The structural chemical simplicity of arylacetamides make them cost-effective alternatives and justifies further improvements to enhance activity, selectivity and the development of pharmaceutical formulations.

Behavioral effects induced by antitumor cleronade diterpenes from Casearia sylvestris and in silico interactions with neuron receptors

ETHNOPHARMACOLOGICAL RELEVANCE

Casearia sylvestris is a medicinal plant traditionally used to treat snakebites, wounds, inflammation and gastric ulcers and scientific supports for have demonstrated its antitumor, antihyperlipidemic and antiparasitic properties.

AIM OF THE STUDY

To assess the effects of a fraction with casearins (FC) on adult mice using classical experimental models of animal behavior and theoretical calculations to verify the interaction of Casearin X (Cas X) with neuron receptors.

MATERIALS AND METHODS

Animals divided in 6 groups (n=9/group) were intraperitoneally treated with vehicle (DMSO 4%), FC (2.5, 5, 10 and 25mg/kg/day) and diazepam (2mg/kg) for 7 days. Thirty minutes after the last dose of treatment, acute toxicity and behavioral experiments were performed.

RESULTS

The highest dose of FC (25mg/kg/day) caused diarrhea, weight loss and death of one animal. Elevated plus maze test showed that lower doses [2.5mg/kg/day (36.4±5.1s) and 5mg/kg/day (43.9±6.2s)] increased the time spent in open arms (TSOA). Open field test revealed reduction in the number of crossings (54.9%, 51.1%, 48% and 67.7% for 2.5, 5, 10 and 25mg/kg/day, respectively) in all doses of FC studied and decrease of rearings at 25mg/kg/day (p<0.05). Computational calculations showed that the inhibition constant (Ki) for the Cas X-D₁ complex is up to 1000-fold more favourable than the Cas X-GABA_A complex. All ∆G° values obtained for Cas X-D₁ complexes were more negative than those seen with Cas X-GABA_A complexes.

CONCLUSIONS

Findings indicate a probable anxiolytic action of the FC since it reduces the number of crossings and rearings and prolonged the time spent in open arms, without sedative and myorelaxant effects, probably due to the interaction of Cas X with dopaminergic system.

Isolation and characterization of 2-pyridone alkaloids and alloxazines from Beauveria bassiana

Two novel compounds bearing heterocyclic nitrogen, 2-pyridone alkaloid (1) and alloxazine derivative (2), along with the known pretenellin B (3), pyridovericin (4) and lumichrome (5) were isolated from a culture of the entomopathogenic fungal strain Beauveria bassiana. The chemical structures of 2-pyridone alkaloid and alloxazine derivative were established on the basis of the interpretation of spectroscopic data. The isolated compounds were evaluated in a panel of five cancer cell lines and pyridovericin exhibited cytotoxicity (IC₅₀, μM) against cancer cell lines: HL-60 (25.9 ± 0.3), HCT8 (34.6 ± 3.6), MDA-MB435 (34.8 ± 3.8) and SF295 (31.1 ± 0.6). Considering that other pyridone compounds display good cytotoxic activity, it would be suggested to obtain new semi synthetic derivatives of pyridovericin, for the development of new cytotoxic chemical entities.

Synthesis, Antitubercular and Anticancer Activities of p-nitrophenylethylenediamine-derived Schiff Bases

BACKGROUND

Schiff bases have been greatly studied in biological field due to their wide range of pharmacological activities, such as antitubercular and antitumour. In the search of novel antitubercular agents, several compounds containing pharmacophoric group of ethambutol have been synthesized and evaluated against mycobacteria species causing tuberculosis. In this work, we investigate whether ethylenediamine, Schiff base as well as nitro group together could contribute to the formation of novel molecules with dual biological activities: antitubercular and anticancer.

METHODS

A series of Schiff bases (3-12) derived from p-nitrophenylethylenediamine (1) as well as N1,N2-bis(4-nitrophenyl)ethane-1,2-diamine (2) were synthetized and assayed for their action against Mycobacterium tuberculosis H37Rv strain and the human tumour cell lines SF-295 (glioblastoma multiforme), HCT-116 (colon adenocarcinoma) and OVCAR-8 (ovarian cancer).

RESULTS

Among the compounds that showed antimycobacterial effects, 4 was more active than ethambutol, the antitubercular drug used as positive control. Also, compounds 1, 8, 10 and 12 were able to reduce strongly the viability of the tumour cell lines at 5 µgmL-1.

CONCLUSION

According to studies, some modifications on p-nitrophenylethylenediamine (1) were an effective strategy to obtain compounds with antiproliferactive activities. Also, Schiff base 4 proved to be the lead antitubercular compound.

Endophytic Actinobacteria from the Brazilian Medicinal Plant Lychnophora ericoides Mart. and the Biological Potential of Their Secondary Metabolites

Endophytic actinobacteria from the Brazilian medicinal plant Lychnophora ericoides were isolated for the first time, and the biological potential of their secondary metabolites was evaluated. A phylogenic analysis of isolated actinobacteria was accomplished with 16S rRNA gene sequencing, and the predominance of the genus Streptomyces was observed. All strains were cultured on solid rice medium, and ethanol extracts were evaluated with antimicrobial and cytotoxic assays against cancer cell lines. As a result, 92% of the extracts showed a high or moderate activity against at least one pathogenic microbial strain or cancer cell line. Based on the biological and chemical analyses of crude extracts, three endophytic strains were selected for further investigation of their chemical profiles. Sixteen compounds were isolated, and 3-hydroxy-4-methoxybenzamide (9) and 2,3-dihydro-2,2-dimethyl-4(1H)-quinazolinone (15) are reported as natural products for the first time in this study. The biological activity of the pure compounds was also assessed. Compound 15 displayed potent cytotoxic activity against all four tested cancer cell lines. Nocardamine (2) was only moderately active against two cancer cell lines but showed strong activity against Trypanosoma cruzi. Our results show that endophytic actinobacteria from L. ericoides are a promising source of bioactive compounds.

Rubrolide analogues and their derived lactams as potential anticancer agents

Analogues of rubrolides were synthesized and shown to be cytotoxic to several cancer cell lines and not toxic to L929 normal cells. The cytotoxicity involved the induction of cell death by apoptosis.

Biomedical properties and potentiality of Lippia microphylla Cham. and its essential oils

Lippia microphylla Cham. (Verbenaceae) is an endemic underexploited Brazilian vegetal. This work reviewed the biological potentialities of Lippia microphylla, emphasizing the properties of essential oils (EOs) and analyzed scientific indicators about genus Lippia and L. microphylla. Databases from 1948 to the present were searched and a software (vantage point 7.1) associated with Derwent Innovation Index was used to identify the indicators of the genus Lippia, and biological activities and compounds in the L. macrophylla species. Ethnopharmacological records report use of L. microphylla leaves to treat gastrointestinal disorders, influenza, bronchitis, cough, nasal congestion, and sinusitis during vaporization, whose aromatic volatile oils are rich in monoterpenes, especially cineole, terpineol, and thymol. Other EOs have larvicidal activity on Aedes aegypti larvae, and antifungal, antibacterial and cytotoxic and antitumor action on human and murine cancer cells. Brazil is the country with more articles about Lippia species, but it deposited only 9 patents since 1993. Most of the publications about L. microphylla are concentrated in food and chemical sciences. This bioprospection helps to choice areas of interest for capital investment and to give support for Brazilian Institutions to establish cooperation and improve technological impact at the point of view of creation and innovation.

Pterocarpans induce tumor cell death through persistent mitotic arrest during prometaphase

Pterocarpans, a family of isoflavonoids found in the diverse Fabaceae, display potent cytotoxic activity over a panel of tumor cell lines, and among those tested, 2,3,9- trimethoxypterocarpan displays the most potent activity. This study evaluates the effects of 2,3,9-trimethoxypterocarpan and its related derivatives on cell cycle progression and microtubule function in select breast cancer cell lines (MCF7, T47d and HS578T). The pterocarpans, with the exception of 3,4-dihydroxy-9-methoxipterocarpan, induced increased frequencies of mitotic cells by inducing arrest in prometaphase. While microtubule organization in interphase cells was not modified during treatment, mitotic cells exhibited high frequencies of monastral spindles surrounded by condensed chromosomes. Immunofluorescence staining with an anti-γ-tubulin antibody showed double-dot labeling in the spindle polar region, suggesting that pterocarpan treatment blocked centrosome segregation. We found that this mitotic arrest was reversible when the cells were treated for up to 24 h followed by recovery in drug-free medium, but not after 48-h treatment followed by incubation in drug-free medium. In that case, treated cells typically underwent cell multinucleation and apoptosis.

Cytotoxic Activity of Pisosterol, a Triterpene Isolated from Pisolithus tinctorius (Mich.: Pers.) Coker & Couch, 1928

Pisolithus tinctorius (Basidiomycete) is an ectomicorrhizal fungus found in the roots and soil surrounding of many species of eucalyptus and pine trees. The present work verified the cytotoxic potential of pisosterol, a triterpene isolated from P. tinctorius collected in the Northeast region of Brazil, on three different animal cell models: mouse erythrocytes, sea urchin embryos and tumor cells. Pisosterol lacked activity on mouse erythrocytes as well as on the development of sea urchin eggs, but strongly inhibited the growth of all seven tumor cell lines tested, especially the leukemia and melanoma cells (IC50 of 1.55, 1.84 and 1.65 μg/ ml for CEM, HL-60 and B16, respectively). The results found for pisosterol were compared with those of doxorubicin and etoposide

Antiproliferative Effects of Several Compounds Isolated from Amburana cearensis A. C. Smith

Amburana cearensis a common tree found in Northeastern Brazil is widely used in folk medicine. The present work evaluated the cytotoxicity of kaempferol, isokaempferide, amburoside A and protocatechuic acid isolated from the ethanol extract of the trunk bark of A. cearensis. The compounds were tested for their cytotoxicity on the sea urchin egg development, hemolysis assay and 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide assay using tumor cell lines. Isokaempferide and kaempferol, but not amburoside A and protocatechuic acid, inhibited the sea urchin egg development as well as tumor cell lines, but in this assay isokaempferide was more potent than kaempferol. Protocatechuic acid was the only compound able to induce hemolysis of mouse erythrocytes, suggesting that the cytotoxicity of kaempferol and isokaempeferide was not related to membrane damage.

Bioactivity of Biflorin, a Typical o-Naphthoquinone Isolated from Capraria biflora L

Capraria biflora L. (Scrophulariaceae) is a perennial shrub widely distributed in several countries of tropical America. The present work verified the cytotoxic and antioxidant potential of biflorin, an o-naphthoquinone isolated from C. biflora collected in the northeast region of Brazil. The cytotoxicity was tested on three different animal cell models: mouse erythrocytes, sea urchin embryos and tumor cells, while the antioxidant activity was assayed by the thiocyanate method. Biflorin lacked activity on mouse erythrocytes as well as on the development of sea urchin eggs, but strongly inhibited the growth of all five tested tumor cell lines, especially the skin, breast and colon cancer cells with IC50 of 0.40, 0.43 and 0.88 μg/ml for B16, MCF-7 and HCT-8, respectively. Biflorin also showed potent antioxidant activity against autoxidation of oleic acid in a water/alcohol system.

Cytotoxic Abietane Diterpenes from Hyptis martiusii Benth

From roots of Hyptis martiusii Benth. two tanshinone diterpenes were isolated, the new 7β-hydroxy-11,14-dioxoabieta-8,12-diene (1) in addition to the known 7α-acetoxy-12-hydroxy- 11,14-dioxoabieta-8,12-diene (7α-acetoxyroyleanone) (2). Structures of 1 and 2 were established by spectroscopic means. The cytotoxic activity against five cancer cell lines was evaluated. Compounds 1 and 2 displayed considerable cytotoxic activity against several cancer cell lines with IC50 values in the range of 3.1 to 11.5 μg/ml and 0.9 to 7.6 μg/ml, respectively. The cytotoxic activity seemed to be related to inhibition of DNA synthesis, as revealed by the reduction of 5-bromo-2′-deoxyuridine incorporation and induction of apoptosis, as indicated by the acridine orange/ethidium bromide assay and morphological changes after 24 h of incubation in leukemic cells.

Studies on the Cytotoxicity of Cucurbitacins Isolated from Cayaponia racemosa (Cucurbitaceae)

The cytotoxic potential of three cucurbitacins, 2,3,16,20(R),25-pentahydroxy-11,22-dioxocucurbita- 5-en (cucurbitacin P, 1), 2,3,16,20(R),25-pentahydroxy-22-oxocucurbita-5-en (2) and 2,3,16,20(R),25-pentahydroxy-22-oxocucurbita-5,23(E)-diene (deacetylpicracin, 3), obtained from Cayaponia racemosa was evaluated as their ability to induce brine shrimp lethality, to inhibit the development of sea urchin eggs and tumor cell proliferation, and to lysis mouse erythrocytes. Compounds 1 and 2 were highly toxic with LC50 of (29.6 ± 9.1) (56.8) and (38.8 ± 3.0) (76.6) μg/mL (μм), respectively, while compound 3 was not effective at the tested concentrations. All tested compounds possessed an inhibitory effect on the proliferation of tumor cell lines, compound 1 being the most active, followed by 2 and 3. Nevertheless, no hemolytic activity or inhibition of the development of sea urchin eggs was observed for these compounds.

Mycoleptones A-C and polyketides from the endophyte Mycoleptodiscus indicus

Three new azaphilones with an unusual methylene bridge, named mycoleptones A, B, and C (2, 4, and 5), were isolated from cultures of Mycoleptodiscus indicus, a fungus associated with the South American medicinal plant Borreria verticillata. Additionally, four known polyketides, austdiol (1), eugenitin (3), 6-methoxyeugenin (6), and 9-hydroxyeugenin (7), were also isolated. The structural characterization of compounds was carried out by nuclear magnetic resonance spectroscopy, high-resolution mass spectrometry, electronic circular dichroism spectroscopy, time-dependent density functional theory calculations, and X-ray crystallography. Compounds 1-9 were weakly active when tested in antileishmanial and cytotoxicity assays.

In vitro and in vivo anticancer properties of cucurbitacin isolated from Cayaponia racemosa

CONTEXT

Cucurbitacins are a group of triterpenoids that have a cucurbitane skeleton with a wide range of biological activities.

OBJECTIVES

This study evaluated the anticancer properties of one cucurbitacin isolated from Cayaponia racemosa Cong. (Cucurbitaceae), 2β,3β,16α,20(R),25-pentahydroxy-22-oxocucurbita-5-en (1), with in vitro and in vivo models.

MATERIALS AND METHODS

In vitro cytotoxic activity was determined with human leukemia (HL60) and normal blood cells (PBMC). Sarcoma 180 was used as in vivo model.

RESULTS

The cucurbitacin (1) reduced the number of viable cells; however, there was no changed in the number of non-viable cells at 5 µg/mL. Selectivity towards cancer cells was suggested by the absence of activity on normal proliferating lymphocytes at the concentrations tested (IC₅₀ >25 µg/ml). Morphological analysis of compound 1-treated cells showed typical apoptotic features, such as intense deposition of granules in the cytoplasm (eosinophilia), DNA fragmentation and irregularities in the plasma membrane. In addition, the cells treated with compound 1 presented intense vacuolization and disruption of the plasma membrane. Acridine orange/Ethidium bromide staining confirmed these findings, revealing an increased number of apoptotic cells. In the Sarcoma 180 tumor model, compound 1 showed 52 and 62% of antitumor activity, either alone (25 mg/kg/day) or in association with the chemotherapeutic agent 5-FU (10 + 10 mg/kg/day), respectively. Moreover, either alone or associated with 5-FU, treatment with compound 1 caused an increase in spleen weight and morphological alterations related to immunostimulatory properties.

CONCLUSION

These data indicate that these naturally occurring compounds have anticancer potential.

Involvement of intrinsic mitochondrial pathway in neosergeolide-induced apoptosis of human HL-60 leukemia cells: the role of mitochondrial permeability transition pore and DNA damage

CONTEXT

Quassinoids are biologically active secondary metabolites found exclusively in the Simaroubaceae family of plants. These compounds generally present important biological properties, including cytotoxic and antitumor properties.

OBJECTIVE

In the present study, the cytotoxic effects of neosergeolide, a quassinoid isolated from Picrolemma sprucei Hook. f., were evaluated in human promyelocytic leukemia cells (HL-60).

MATERIALS AND METHODS

Cytotoxicity and antiproliferative effects were evaluated by the MTT assay, May-Grünwald-Giemsa's staining, BrdU incorporation test, and flow cytometry procedures. The comet assay and micronuclei analysis were applied to determine the genotoxic and mutagenic potential of neosergeolide.

RESULTS

After 24 h exposure, neosergeolide strongly inhibited cancer cell proliferation (IC₅₀ 0.1 µM), and its activity seemed to be selective to tumor cells because it had no antiproliferative effect on human peripheral blood mononuclear cells (PBMC) at tested concentrations. Apoptosis was induced at submicromolar concentrations (0.05, 0.1, and 0.2 µM) as evidenced by morphological changes, mitochondrial depolarization, phosphatidylserine externalization, caspases activation, and internucleosomal DNA fragmentation. Additionally, neosergeolide effects were prevented by cyclosporine A (CsA), an inhibitor of the mitochondrial permeability transition (MPT) pore, which reinforced the participation of intrinsic pathways in the apoptotic process induced by this natural quassinoid. Direct DNA damage was further confirmed by comet assay and cytokinesis-block micronucleus test.

DISCUSSION AND CONCLUSION

The present study provided experimental evidence to support the underlying mechanism of action involved in the neosergeolide-mediated apoptosis. In addition, no antiproliferative effect or DNA damage effect of neosergeolide was evident in PBMC, highlighting its therapeutic potential.

Antiproliferative effects of lectins from Canavalia ensiformis and Canavalia brasiliensis in human leukemia cell lines

The antiproliferative activity of lectins Canavalia ensiformis (ConA) and Canavalia brasiliensis (ConBr) were studied using human leukemia MOLT-4 and HL-60 cell lines. It was revealed that both ConA and ConBr were markedly cytotoxic to cells using MTT and NAC assays. The IC(50) values were approximately 3 and 20 μg/mL for ConA and ConBr, respectively, for both MOLT-4 and HL-60 cells. However, in normal human peripheral blood lymphocytes, the lectins were not cytotoxic, even when tested at concentrations as high as 200 μg/ml. Using comet assay, the lectins produced a rate of DNA damage exceeding 80% in MOLT-4 and HL-60 cells. Fluorescence analysis revealed the morphology characteristic of apoptosis, with low concentrations of apoptotic bodies and fragmented DNA (5 μg/ml). Flow cytometric analysis demonstrated an accumulation of cells in the sub-G1 cell cycle that is characteristic of DNA fragmentation, and a decrease in membrane integrity at high concentrations. Lastly, we evaluated the alterations in mitochondrial potential that reduced after treatment with lectins. Our results indicate that ConA and ConBr inhibited cell proliferation selectively in tumor cells and that apoptosis was the main death mechanism. Therefore, lectins can be considered a class of molecules with a high antitumor activity potential.

Synthesis and cytotoxic activity of new acridine-thiazolidine derivatives

Although their exact role in controlling tumour growth and apoptosis in humans remains undefined, acridine and thiazolidine compounds have been shown to act as tumour suppressors in most cancers. Based on this finding, a series of novel hybrid 5-acridin-9-ylmethylene-3-benzyl-thiazolidine-2,4-diones were synthesised via N-alkylation and Michael reaction. The cell viability was analysed using a 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, and DNA interaction assays were performed using electrochemical techniques.

Genetic toxicology evaluation of essential oil of Alpinia zerumbet and its chemoprotective effects against H(2)O(2)-induced DNA damage in cultured human leukocytes

Essential oil (EO) of Alpinia zerumbet leaves, at non-toxic concentrations (50-300 μg/mL), did not induce genotoxicity in human leukocytes. However, at the highest concentration (500 μg/mL) tested caused a reduction in cell proliferation and viability, and an increase in DNA damage. Moreover, in vivo experiments showed that EO (400 mg/kg) did not exert mutagenicity on peripheral blood cells and bone marrow in mice. In DPPH test, EO showed scavenging effects against DPPH radicals, and other free radicals (determination of intracellular GSH and lipid peroxidation assays). Furthermore, EO was able to reduce the intracellular levels of ROS, and prevented leukocytes DNA against oxidative damage. The ability of EO to reduce H(2)O(2) toxicity was observed only when cells were treated with EO during and after exposure to H(2)O(2). With the co- and post-treatment procedures, EO decreased the frequency of apoptotic and micronucleated leukocytes as well DNA strand breaks. However, a synergistic effect was observed in cultures exposed to 500 μg/mL EO. In conclusion, EO at concentrations up to 300 μg/mL or doses up to 400mg/kg are not mutagenic in leukocytes and in mice, but do have antioxidative and protective effects against the cytotoxicity and clastogenesis induced by H(2)O(2).