Jayaraman Vinayagam

Hydroxychavicol, a Piper betle leaf component, induces apoptosis of CML cells through mitochondrial reactive oxygen species-dependent JNK and endothelial nitric oxide synthase activation and overrides imatinib resistance.

Alcoholic extract of Piperbetle (Piper betle L.) leaves was recently found to induce apoptosis of CML cells expressing wild type and mutated Bcr‐Abl with imatinib resistance phenotype. Hydroxychavicol (HCH), a constituent of the alcoholic extract of Piper betle leaves, was evaluated for anti‐CML activity. Here, we report that HCH and its analogues induce killing of primary cells in CML patients and leukemic cell lines expressing wild type and mutated Bcr‐Abl, including the T315I mutation, with minimal toxicity to normal human peripheral blood mononuclear cells. HCH causes early but transient increase of mitochondria‐derived reactive oxygen species. Reactive oxygen species‐dependent persistent activation of JNK leads to an increase in endothelial nitric oxide synthase‐mediated nitric oxide generation. This causes loss of mitochondrial membrane potential, release of cytochrome c from mitochondria, cleavage of caspase 9, 3 and poly‐adenosine diphosphate‐ribose polymerase leading to apoptosis. One HCH analogue was also effective in vivo in SCID mice against grafts expressing the T315I mutation, although to a lesser extent than grafts expressing wild type Bcr‐Abl, without showing significant bodyweight loss. Our data describe the role of JNK‐dependent endothelial nitric oxide synthase‐mediated nitric oxide for anti‐CML activity of HCH and this molecule merits further testing in pre‐clinical and clinical settings. (Cancer Sci 2012; 103: 88–99)

ICB3E induces iNOS expression by ROS-dependent JNK and ERK activation for apoptosis of leukemic cells

The role of c-Jun N terminal Kinase (JNK) has been well documented in various cellular stresses where it leads to cell death. Similarly, extracellular signal-regulated kinase (ERK) which was identified as a signalling molecule for survival pathway has been shown recently to be involved in apoptosis also. Recently we reported that ICB3E, a synthetic analogue of Piper betle leaf-derived apoptosis-inducing agent hydroxychavicol (HCH), possesses anti-chronic myeloid leukemia (CML) acitivity in vitro and in vivo without insight on mechanism of action. Here we report that ICB3E is three to four times more potent than HCH in inducing apoptosis of leukemic cells without having appreciable effects on normal human peripheral blood mononuclear cells, mouse fibroblast cell line NIH3T3 and monkey kidney epithelial cell line Vero. ICB3E causes early accumulation of mitochondria-derived reactive oxygen species (ROS) in K562 cells. Unlike HCH, ICB3E treatment caused ROS dependent activation of both JNK, ERK and induced the expression of iNOS leading to generation of nitric oxide (NO). This causes cleavage of caspase 9, 3 and PARP leading to apoptosis. Lack of cleavage of caspase 8 and inability of blocking chimera antibody to DR5 or neutralizing antibody to Fas to reverse ICB3E-mediated apoptosis suggest the involvement of only intrinsic pathway. Our data reveal a novel ROS-dependent JNK/ERK-mediated iNOS activation pathway which leads to NO mediated cell death by ICB3E.

Isobenzofuranone derivatives exhibit antileishmanial effect by inhibiting type II DNA topoisomerase and inducing host response

Leishmania, a protozoan parasite, causes a wide range of human diseases ranging from the localized self‐healing cutaneous lesions to fatal visceral leishmaniasis. Toxicity of traditional first line drugs and emergence of drug‐resistant strains have worsened the situation. DNA topoisomerase II in kinetoplastid protozoan parasites are of immense interest as drug target because they take part in replication of unusual kinetoplast DNA network. In this study, we have taken target‐based therapeutic approaches to combat leishmaniasis. Two isobenzofuranone compounds, viz., (1) 3,5‐bis(4‐chlorophenyl)‐7‐hydroxyisobenzofuran‐1(3H)‐one (JVPH3) and (2) (4‐bromo)‐3′‐hydroxy‐5′‐(4‐bromophenyl)‐benzophenone(JVPH4) were synthesized chemically and characterized by NMR and mass spectrometry analysis. Activity of type II DNA topoisomerase of leishmania (LdTOPII) was monitored by decatenation assay and plasmid cleavage assay. The antiparasitic activity of these compounds was checked in experimental BALB/c mice model of visceral leishmaniasis. Isobenzofuranone derivatives exhibited potent antileishmanial effect on both antimony (Sb) sensitive and resistant parasites. Treatment with isobenzofuranone derivatives on promastigotes caused induction of reactive oxygen species (ROS)‐mediated apoptosis like cell death in leishmania. Both the compounds inhibited the decatenation activity of LdTOPII but have no effect on bi‐subunit topoisomerase IB. Treatment of LdTOPII with isobenzofuranone derivatives did not stabilize cleavage complex formation both in vitro and in vivo. Moreover, treatment with isobenzofuranone derivatives on Leishmania donovani‐infected mice resulted in clearance of parasites in liver and spleen by induction of Th1 cytokines. Taken together, our data suggest that these compounds can be exploited as potential antileishmanial agents targeted to DNA topoisomerase II of the parasite.

InCl3 Catalysed One-Pot Synthesis of Substituted Pyrroles and 2-Pyrones

An efficient InCl3 catalysed one-pot strategy has been developed for the synthesis of tetra-substituted pyrroles and tri-substituted 2-pyrones in very good yields. Tetra-substituted pyrroles were prepared from 1,4-enediones and β-dicarbonyls employing NH4OAc as a nitrogen source, through a combination of Michael addition and Paal–Knorr methods. Tri-substituted 2-pyrones were synthesised from 1,4-ynediones and appropriate β-dicarbonyls using a sequential Michael addition and 6-exo-trig cyclisation.

Antibacterial Activity and Anticorrosive Efficiency of Aqueous Methanolic Extract of Artemisia pallens (Asteraceae) and its major Constituent

An aqueous-methanolic [methanol:water (1:1)] extract of the whole plant of Artemisia pallens (Family: Asteraceae) has shown good antibacterial activity against Pseudomonas aeruginosa and Shigella flexneri at the concentration of 100 mg/mL. The activity-guided fractionation has led to isolation of compound 4-hydroxyphenyl-?-D-glucopyranoside (which is known as arbutin), as a major constituent and exhibited the same antibacterial activity at a concentration of 17 mg/mL. Both the crude extract and arbutin also showed 94% anticorrosive efficiency against mild steel in 1M HCl at concentration of 200 mg/L.

Isobenzofuranone derivative JVPH3, an inhibitor of L. donovani topoisomerase II, disrupts mitochondrial architecture in trypanosomatid parasites

Kinetoplast DNA (kDNA) bearing unusual mitochondrion of trypanosomatid parasites offers a new paradigm in chemotherapy modality. Topoisomerase II of Leishmania donovani (LdTopII), a key enzyme associated with kDNA replication, is emerging as a potential drug target. However, mode of action of LdTopII targeted compounds in the parasites at sub-cellular level remains largely unknown. Previously, we reported that an isobenzofuranone derivative, namely 3,5-bis(4-chlorophenyl)-7-hydroxyisobenzofuran-1(3H)-one (JVPH3), targets LdTopII and induces apoptosis-like cell death in L. donovani. Here, we elucidate the phenotypic changes and the events occurring at sub-cellular level caused by JVPH3 in L. donovani. In addition, we have evaluated the cytotoxicity and ultrastructural alterations caused by JVPH3 in two brazilian trypanosomatid pathogens viz. L. amazonensis and Trypanosoma cruzi. Despite killing these parasites, JVPH3 caused significantly different phenotypes in L. donovani and L. amazonensis. More than 90% population of parasites showed altered morphology. Mitochondrion was a major target organelle subsequently causing kinetoplast network disorganization in Leishmania. Altered mitochondrial architecture was evident in 75–80% Leishmania population being investigated. Quantification of mitochondrial function using JC-1 fluorophore to measure a possible mitochondrial membrane depolarization further confirmed the mitochondrion as an essential target of the JVPH3 corroborating with the phenotype observed by electron microscopy. However, the impact of JVPH3 was lesser on T. cruzi than Leishmania. The molecule caused mitochondrial alteration in 40% population of the epimastigotes being investigated. To our knowledge, this is the first report to evaluate the proliferation pattern and ultrastructural alterations caused in Brazilian kinetoplastid pathogens by a synthetic LdTopII inhibitor previously established to have promising in vivo activity against Indian strain of L. donovani.

Substituted furans as potent lipoxygenase inhibitors: Synthesis, in vitro and molecular docking studies

A number of 2-methyl-4-(2-oxo-2-phenyl-ethyl)-5-phenyl-furan-3-carboxylic acid alkyl ester derivatives (3a-j) were synthesized and evaluated for their in vitro inhibitory activity on soybean lipoxygenase enzyme. Among the screened compounds, 5-(4-bromo-phenyl)-4-[2-(4-bromo-phenyl)-2-oxo-ethyl]-2-methyl-furan-3-carboxylic acid methyl ester (3g) has been found to exhibit potent inhibitory activity with IC5012.8μM using nordihydroguaiaretic acid (NDGA) as standard. Molecular modeling was employed for better understanding of the binding between compounds and soybean lipoxygenase enzyme. The predicted binding energy values correlated well with the observed in vitro data.