Carlos A. Bueno

Cytotoxic Tirucallane Triterpenoids from Melia azedarach Fruits

The phytochemical investigation of the dichloromethane-soluble part of the methanol extract obtained from the fruits of Melia azedarach afforded one new tirucallane-type triterpene, 3-α-tigloylmelianol (1) and three known tirucallanes, melianone (2), 21-β-acetoxy-melianone (3), and methyl kulonate (4). The structure of the isolated compounds was mainly determined by 1D and 2D NMR experiments as well as HPLC-Q-TOF mass spectrometry. The cytotoxicity of the isolated compounds toward the human lung adenocarcinoma epithelial cell line A549 was determined, while no activity was observed against the phytonematode Meloidogyne incognita.

A natural tetranortriterpenoid with immunomodulating properties as a potential anti-HSV agent

Abstract Meliacine (MA), an antiviral principle present in partially purified leaf extracts of Melia azedarach L., prevents the development of herpetic stromal keratitis (HSK) in mice by diminishing the viral load in the eye and the severity of lesions caused by a virus-induced immunopathological reaction. The tetranortriterpenoid 1-cinnamoyl-3,11-dihydroxymeliacarpin (CDM), obtained from MA purification, displays anti-herpetic activity and impedes nuclear factor κB (NF-κB) activation in HSV-1 infected conjunctival cells. To extend our understanding about CDM biological properties, we investigated its anti-HSV-1 activity as well as the effect on NF-κB activation and cytokine secretion induced by viral (HSV-1) and no-viral (LPS) stimuli, in corneal cells and macrophages. CDM exerted a potent anti-HSV-1 effect on corneal cells and inhibited NF-κB translocation to the nucleus, leading to a decrease in IL-6 production. Besides, CDM seemed to modulate IL-6 and TNF-α responses in macrophages, whether they were infected with HSV-1 or stimulated with LPS. However, CDM did not affect NF-κB activation in these cells, suggesting that an alternative NF-κB cell signaling pathway would be involved in the modulation of cytokine production. We conclude that, in addition to its antiviral effect, CDM would be acting as an immunomodulating compound which would be responsible for the improvement of murine HSK already reported.

Antiproliferative, cytotoxic and hemolytic activities of a triterpene glycoside from Psolus patagonicus and its desulfated analog.

Background: The major triterpene glycoside of the sea cucumber Psolus patagonicus and its desulfated analog were tested for their antiproliferative, cytotoxic and hemolytic activities, and their effect on NF-κB activation. Methods: The antiproliferative action of glycosides 1 and 2 were determined on 3 tumor cell lines. Their effect on the activation of NF-κB was evaluated by indirect immunofluorescence assay staining and the concomitant IκBα degradation was studied by Western blot. Results: Both compounds were able to suppress the growth of 3 tumor cell lines (Hep3B, MDA-MB231 and A549) and induced the activation of NF-κB, a key player linking chronic inflammation and cancer, concomitant with IκBα degradation in the A549 tumor cell line. Compounds 1 and 2 showed hemolytic activity with half maximal inhibitory concentration (IC50) values around 80 μM. Conclusions: Both glycosides showed low cytotoxic activity in A549 tumor cells in comparison with sea cucumber triterpene glycosides containing a linear tetrasaccharide chain. This could be a result of the uncommon presence of two 12α- and 17α-hydroxyl groups and a Δ7 double bond in the aglycone moiety. This aglycone functionalization may be related to their low membranolytic activity. Although glycosides 1 and 2 exert an antiproliferative effect, their mechanisms of action do not involve inhibition of NF-κB. Recently, it has been shown that diverse and new mechanisms of action are responsible for the antitumor and cytotoxic activities of marine compounds. Therefore, more extensive studies are needed to establish a mechanism of action and to deduce a clear structure-activity relationship of sea cucumber triterpene glycosides.

Pseudocnoside A, a new cytotoxic and antiproliferative triterpene glycoside from the sea cucumber Pseudocnus dubiosus leoninus

A new triterpene glycoside, pseudocnoside A (1), was isolated from the sea cucumber Pseudocnus dubiosus leoninus. The structure of the new compound was established on the basis of extensive NMR spectroscopic analysis (1H and 13C NMR, 1H,1H-COSY, HMBC, HSQC, TOCSY and NOESY), HR-ESI-MS data and chemical transformations. In addition, the cytotoxicity and antiproliferative activities of 1 and structurally related triterpene glycosides isolated from the sea cucumbers Psolus patagonicus and Hemioedema spectabilis were evaluated against cancer cell lines A-549 and HeLa.

1-Cinnamoyl-3,11-dihydroxymeliacarpin delays glycoprotein transport restraining virus multiplication without cytotoxicity

The 1-cinnamoyl-3,11-dihydroxymeliacarpin (CDM), isolated from extracts of Melia azedarach L., displays antiviral and immunomodulating properties. CDM is the first reported tetranortriterpenoid responsible for the alkalinization of intracellular compartments affecting both, viral endocytic and exocytic pathways. Considering that viral glycoprotein synthesis is completely dependent upon cellular membrane trafficking, we questioned whether CDM might also interfere with the normal transport of cellular glycoproteins. This study demonstrates that CDM promoted a transient block in the transport of two cellular glycoproteins, the transferrin receptor (TfR) and TNF-alpha. Nevertheless, CDM did not affect the transferrin binding ability of TfR and did not impede the TNF-alpha secretion. On the other hand, CDM disturbed the intracellular localization of capsid, glycoprotein and tegument proteins simultaneously in the same HSV-1 infected cells. Besides, we show that concanamycin A and monensin provoke a permanent blockage of viral and cellular glycoproteins, in contrast to the delay observed after CDM treatment. Thus, the delay on glycoprotein transport caused by CDM would account for the strong inhibition on virus multiplication without interfering with the bioactivity of cellular glycoproteins.

A natural antiviral and immunomodulatory compound with antiangiogenic properties

Meliacine (MA), an antiviral principle present in partially purified leaf extracts of Melia azedarach L., reduces viral load and abolishes the inflammatory reaction and neovascularization during the development of herpetic stromal keratitis in mice. 1-cinnamoyl-3,11-dihydroxymeliacarpin (CDM), obtained from MA, displays anti-herpetic and immunomodulatory activities in vitro. We investigated whether CDM interferes with the angiogenic process. CDM impeded VEGF transcription in LPS-stimulated and HSV-1-infected cells. It proved to have neither cytotoxic nor antiproliferative effect in HUVEC and to restrain HUVEC migration and formation of capillary-like tubes. Moreover, MA inhibits LMM3 tumor-induced neovascularization in vivo. We postulate that the antiangiogenic activity of CDM displayed in vitro as a consequence of their immunomodulatory properties is responsible for the antiangiogenic activity of MA in vivo, which would be associated with the lack of neovascularization in murine HSV-1-induced ocular disease.

Synthetic stigmastanes with dual antiherpetic and immunomodulating activities inhibit ERK and Akt signaling pathways without binding to glucocorticoid receptors.

BACKGROUND We have previously shown that some synthetic hydroxylated stigmastanes derived from plant sterols inhibit in vitro HSV-1 replication in ocular cell lines and decrease cytokine production in stimulated macrophages, suggesting that these steroids might combine antiviral and immunomodulating properties. In this paper we report the synthesis of some analogs fluorinated at C-6 in order to study the effect of this modification on bioactivity. METHODS The following methods were used: organic synthesis of fluorinated analogs, cytotoxicity determination with MTT assays, cytokine production quantification with ELISAs, glucocorticoid activity determination by displacement assays, immunofluorescence and transcriptional activity assays, studies of the activation of signaling pathways by Western blot, antiviral activity evaluation through virus yield reduction assays. RESULTS We report the chemical synthesis of new fluorinated stigmastanes and show that this family of steroidal compounds exerts its immunomodulating activity by inhibiting ERK and Akt signaling pathways, but do not act as glucocorticoids. We also demonstrate that fluorination enhances the antiviral activity. CONCLUSIONS Fluorination on C-6 did not enhance the anti-inflammatory effect, however, an increase in the in vitro antiviral activity was observed. Thus, our results suggest that it is possible to introduce chemical modifications on the parent steroids in order to selectively modulate one of the effects. GENERAL SIGNIFICANCE This family of steroids could allow the development of an alternative treatment for ocular immunopathologies triggered by HSV-1, without the undesirable side effects of the currently used drugs.

Synthetic stigmasterol derivatives inhibit capillary tube formation, herpetic corneal neovascularization and tumor induced angiogenesis: Antiangiogenic stigmasterol derivatives.

Angiogenesis plays a critical role in initiating and promoting several diseases, such as cancer and herpetic stromal keratitis (HSK). Herein, we studied the inhibitory effect of two synthetic stigmasterol derivatives on capillary tube-like structures and on cell migration in human umbilical vein endothelial cells (HUVEC): (22S,23S)-22,23-dihydroxystigmast-4-en-3-one (compound 1) and (22S,23S)-3β-bromo-5α,22,23-trihydroxystigmastan-6-one (compound 2). We also studied their effect on VEGF expression in IL-6 stimulated macrophages and in LMM3 breast cancer cells. Furthermore, we investigated the antiangiogenic activity of the compounds on corneal neovascularization in the murine model of HSK and in an experimental model of tumor-induced angiogenesis in mice. Both compounds inhibited capillary tube-like formation, but only compound 1 restrained cell migration. Compound 1, unlike compound 2, was able to reduce VEGF expression. Only compound 1 not only reduced the incidence and severity of corneal neovascularization, when administered at the onset of HSK, but it also restrained the development of neovascular response induced by tumor cells in mice skin. Our results show that compound 1 inhibits angiogenesis in vitro and in vivo. Therefore, compound 1 would be a promising drug in the treatment of those diseases where angiogenesis represents one of the main pathogenic events.

Virucidal, antiviral and immunomodulatory activities of β-escin and Aesculus hippocastanum extract

β‐Escin, one of the constituents of Aesculus hippocastanum L. (Hippocastanaceae) seed extract (AH), inhibits NF‐κB activation, which plays an important role in HSV‐1 replication. The aim was to examine the antiherpetic activity of β‐escin and AH, as well as their effect on the activation of NF‐κB and AP‐1 and cytokine secretion in epithelial cells and macrophages.