The Bioflavonoids Rutin and Rutin Succinate Neutralize the Toxins of B. jararaca Venom and Inhibit its Lethality

The venom of the Brazilian pit viper Bothrops jararaca (BjV) is a complex mixture of molecules, and snake venom metalloproteinases (SVMP) and serine proteinases (SVSP) are the most abundant protein families found therein. Toxins present in BjV trigger most of the deleterious disturbances in hemostasis observed in snakebites, i.e., thrombocytopenia, hypofibrinogenemia and bleedings. The treatment of patients bitten by snakes still poses challenges and the bioflavonoid rutin has already been shown to improve hemostasis in an experimental model of snakebite envenomation. However, rutin is poorly soluble in water; in this study, it was succinylated to generate its water-soluble form, rutin succinate (RS), which was analyzed comparatively regarding the chemical structure and characteristic features of rutin. Biological activities of rutin and RS were compared on hemostatic parameters, and against toxic activities of crude BjV in vitro. In vivo, C57BL/6 mice were injected i.p. with either BjV alone or pre-incubated with rutin, RS or 1,10-phenanthroline (o-phe, an SVMP inhibitor), and the survival rates and hemostatic parameters were analyzed 48 h after envenomation. RS showed the characteristic activities described for rutin – i.e., antioxidant and inhibitor of protein disulfide isomerase – but also prolonged the clotting time of fibrinogen and plasma in vitro. Differently from rutin, RS inhibited typical proteolytic activities of SVMP, as well as the coagulant activity of BjV. Importantly, both rutin and RS completely abrogated the lethal activity of BjV, in the same degree as o-phe. BjV induced hemorrhages, falls in RBC counts, thrombocytopenia and hypofibrinogenemia in mice. Rutin and RS also improved the recovery of platelet counts and fibrinogen levels, and the development of hemorrhages was totally blocked in mice injected with BjV incubated with RS. In conclusion, RS has anticoagulant properties and is a novel SVMP inhibitor. Rutin and RS showed different mechanisms of action on hemostasis. Only RS inhibited directly BjV biological activities, even though both flavonoids neutralized B. jararaca toxicity in vivo. Our results showed clearly that rutin and RS show a great potential to be used as therapeutic compounds for snakebite envenomation.

Biogenic Aspergillus tubingensis silver nanoparticles' in vitro effects on human umbilical vein endothelial cells, normal human fibroblasts, HEPG2, and Galleria mellonella

Silver nanoparticles (AgNPs) are widely incorporated into different hygiene, personal care, and healthcare products. However, few studies have been undertaken to determine the effects of biogenic AgNPs on human health. The effect of biosynthesized AgNPs using the fungus Aspergillus tubingensis culture was evaluated on human umbilical vein endothelial cells (HUVECs), normal human fibroblasts (FN1), human hepatoma cells (HEPG2) and a Galleria mellonella model. HUVECs were more susceptible to biogenic AgNPs than normal fibroblasts FN1 and intense cytotoxicity was observed only for very high concentrations at and above 2.5 μM for both cells. Normal human fibroblasts FN1 exposed to AgNPs for 24 h showed viability of 98.83 ± 8.40% and 94.86 ± 5.50% for 1.25 and 2.5 μM, respectively. At 5 and 10 μM, related to the control, an increase in cell viability was observed being 112.66 ± 9.94% and 117.86 ± 8.86%, respectively. Similar results were obtained for treatment for 48 and 72 h. At 1.25, 2.5, 5 and 10 μM of AgNPs, at 24 h, HUVECs showed 51.34 ± 7.47%, 27.01 ± 5.77%, 26.00 ± 3.03% and 27.64 ± 5.85% of viability, respectively. No alteration in cell distribution among different cycle phases was observed after HUVEC and normal fibroblast FN1 exposure to AgNPs from 0.01 to 1 μM for 24, 48 and 72 h. Based on the clonogenic assay, nanoparticles successfully inhibited HEPG2 cell proliferation when exposed to concentrations up to 1 μM. In addition to that, AgNPs did not induce senescence and no morphological alteration was observed by scanning electron microscopy on the endothelial cells. In the larvae of the wax moth, Galleria mellonella, a model for toxicity, AgNPs showed no significant effects, which corroborates to the safety of their use in mammalian cells. These results demonstrate that the use of A. tubingensis AgNPs is a promising biotechnological approach and these AgNPs can be applied in several biomedical situations.

Investigation of local anesthetic and antimycobacterial activity of Ottonia martiana Miq. (Piperaceae)

Ottonia martiana is a plant popularly known in Brazil by the use for toothache. Ethanolic extract (EE), hexane fraction (HF), dichloromethane fraction (DF) and piperovatine obtained from O. martiana were assayed in vitro and in vivo. The acute toxicity of EE was determined, and LD50 values of 164.5 and 65.0 mg/kg by the oral and intraperitoneal routes, respectively, indicated a high toxicity for EE in vivo, explaining its popular use by topical administration only. A local anesthetic-like effect of EE and its fractions was observed in experimental models using pain induction, and such effect involved an analgesic action. The antimycobacterial activity of EE, HF, DF and piperovatine was evaluated against Mycobacterium tuberculosis H37Rv ATCC 27924. EE, HF, DF, and piperovatine showed a potential antimycobacterial effect with MICs of 16.0, 62.0, 62.0 and 8.0 μg/mL, respectively. Piperovatine was more effective than the EE or the other fractions. The selectivity index (SI=IC50/MIC) values calculated for EE, HF, DF and piperovatine based on the MICs and the cytotoxicity against J774 macrophages (IC50 by MTT assay) revealed values of 6.43, 2.34, 1.5 and 9.66, respectively.

Effects of the antimycobacterial compound 2-phenoxy-1-phenylethanone on rat hepatocytes and formation of metabolites

CONTEXT

Neolignans are usually dimers formed by oxidative coupling of allyl and propenyl phenols, and the neolignan analogue, 2-phenoxy-1-phenylethanone (LS-2) is a promising antimycobacterial compound showing very weak cytotoxicity in mammalian cells and lack of acute toxicity in murine models.

OBJECTIVES

To investigate the mechanism of action of LS-2 in rat hepatocytes by evaluating the activity levels of enzymes related to oxidation status and drug-metabolizing activity.

MATERIALS AND METHODS

Hepatocytes were treated with LS-2 from 0.05 up to 1 mM, for 24 and 48 h, and reduced glutathione (GSH), lipid peroxidation and cytochrome P450 enzyme (CYP450) activity were assayed. A homologous series of phenoxazone ethers were used as substrates to measure the enzymatic profile. The biotransformation of LS-2 was studied in hepatocytes by gas chromatography-mass spectrometry (GC-MS) for detection and analysis of possible metabolites.

RESULTS

Hepatocytes treated with LS-2 up to 1 mM for 24 or 48 h did not induce the formation of GSH and lipid peroxidation. O-Dealkylation activities of the isoenzymes CYP4501A1, CYP4501A2, CYP4502B1 and CYP4502B2 were also not detected in the hepatocytes treated with LS-2 for 24 or 48 h.

DISCUSSION AND CONCLUSION

The results indicate that LS-2 or its two detected metabolites, 2-phenoxy-1-phenylethanol and 2,4-(2-hydroxy-2-phenylethoxy)phenol, are not cytotoxic to rat hepatocytes. These compounds maintain a balance between the production of pro-oxidant agents and their respective antioxidant systems. The data show that enzymes related to oxidation status and drug-metabolizing activities are not involved in the mechanism of action of LS-2.

Structure activity relationship, acute toxicity and cytotoxicity of antimycobacterial neolignan analogues

OBJECTIVES

The study's aims were to evaluate the antimycobacterial activity of 13 synthetic neolignan analogues and to perform structure activity relationship analysis (SAR). The cytotoxicity of the compound 2-phenoxy-1-phenylethanone (LS-2, 1) in mammalian cells, such as the acute toxicity in mice, was also evaluated.

METHODS

The extra and intracellular antimycobacterial activity was evaluated on Mycobacterium tuberculosis H37Rv. Cytotoxicity studies were performed using V79 cells, J774 macrophages and rat hepatocytes. Additionally, the in-vivo acute toxicity was tested in mice. The SAR analysis was performed by Principal Component Analysis (PCA).

KEY FINDINGS

Among the 13 analogues tested, LS-2 (1) was the most effective, showing promising antimycobacterial activity and very low cytotoxicity in V79 cells and in J774 macrophages, while no toxicity was observed in rat hepatocytes. The selectivity index (SI) of LS-2 (1) was 91 and the calculated LD50 was 1870 mg/kg, highlighting the very low toxicity in mice. SAR analysis showed that the highest electrophilicity and the lowest molar volume are physical-chemical characteristics important for the antimycobacterial activity of the LS-2 (1).

CONCLUSIONS

LS-2 (1) showed promising antimycobacterial activity and very weak cytotoxicity in cell culture, as well as an absence of toxicity in primary culture of hepatocytes. In the acute toxicity study there was an indication of absence of toxicity on murine models, in vivo.

Antimycobacterial brominated metabolites from two species of marine sponges

A screening of 500 crude extracts of marine invertebrates against the growth of Mycobacterium tuberculosis H37Rv yielded MeOH extracts of the sponges Aplysina cauliformis and Pachychalina sp. with significant activity. Further bioassay-guided fractionation of both crude extracts led to the isolation of four bromine-containing metabolites. The known (+)-fistularin-3 (1) and 11-deoxyfistularin-3 (2), and the new compound 2-(3-amino-2,4-dibromo-6-hydroxyphenyl)acetic acid (3) were isolated from the sponge A. cauliformis, while the new bromotyrosine-derived 3-(3,5-dibromo-4-methoxyphenyl)-2-methoxy- N-methylpropan-1-ammonium (4) was isolated from Pachychalina sp. Compound 4 exhibited weak antimycobacterial activity while compounds 1-3 displayed activity against Mycobacterium tuberculosis H37Rv, with MICs of 7.1, 7.3 and 49 microM, respectively. Compounds 1 and 2 also exhibited low cytotoxicity against J744 macrophages, indicating that both 1 and 2 are interesting leads for the development of new anti-tuberculosis agents.

Antimicrobial and Antimycobacterial Activity of Cyclostellettamine Alkaloids from Sponge Pachychalina sp

Cyclostellettamines A – F (1 – 6) isolated from the sponge Pachychalina sp. and cyclostellettamines G - I, K and L (7 – 11) obtained by synthesis were evaluated in bioassays of antimicrobial activity against susceptible and antibiotic-resistant Staphylococcus aureus, Pseudomonas aeruginosa and antibiotic-susceptible Escherichia coli and Candida albicans, as well as in antimycobacterial activity against Mycobacterium tuberculosis H37Rv bioassays. The results obtained indicated that cyclostellettamines display different antimicrobial activity depending on the alkyl-chain size, suggesting that, if a mechanism-of action is implied, it is dependent on the distance between the two pyridinium moieties of cyclostellettamines.