Paul Kong Thoo Lin

Cytotoxicity, DNA binding and localisation of novel bis-naphthalimidopropyl polyamine derivatives.

Bis-naphthalimidopropyl spermidine (BNIPSpd), spermine (BNIPSpm) and oxa-spermine (BNIPOSpm) showed high in vitro cytotoxicity against human breast cancer MCF-7 cells with IC(50) values of 1.38, 2.91 and 8.45 microM, respectively. These compounds were found to effectively displace the intercalating agent ethidium bromide bound to the calf thymus DNA using fluorimetric methods (C(50) 0.08-0.12 microM) and their apparent equilibrium binding constants (K(app)) were calculated to be in the range of 10.5-18 x 10(7) M(-1). Furthermore, strong stabilisation of calf thymus DNA duplex in the presence of bis-naphthalimidopropyl polyamine derivatives (BNIPSpd, BNIPSpm and BNIPOSpm) was observed by UV spectrophotometric analysis (T(m)=93.3-97 degrees C compared with 75 degrees C for calf thymus DNA without drug). Because of their inherent fluorescence, these compounds were localised preferentially inside the nucleus as evidenced by their direct observation under the fluorescence microscope. The results obtained suggest that the cytotoxic activity of the bis-naphthalimidopropyl polyamines may be in part, caused by their effects on DNA.

The synthesis and in vitro cytotoxic studies of novel bis-naphthalimidopropyl polyamine derivatives.

Bis-naphthalimidopropyl putrescine (BNIPPut), spermidine (BNIPSpd), spermine (BNIPSpm) and oxa-putrescine (BNIPOPut) were synthesised and their growth-inhibitory properties characterised. All these compounds except for BNIPOPut, showed high in vitro cytotoxic activity (with mean GI50 values between 0.5 and 8.45 microM) and selectivity against cancer cells derived from nine different human tumours. The increased content of nitrogen atoms in the linker chain of BNIPSpd and BNIPSpm significantly improved their aqueous dissolution properties with a marginal decrease in their cytotoxic activity.

Bisnaphthalimidopropyl Derivatives as Inhibitors of Leishmania SIR2 Related Protein 1

The NAD+‐dependent deacetylases, namely sirtuins, are involved in the regulation of a variety of biological processes such as gene silencing, DNA repair, longevity, metabolism, apoptosis, and development. An enzyme from the parasite Leishmania infantum that belongs to this family, LiSIR2RP1, is a NAD+‐dependent tubulin deacetylase and an ADP‐ribosyltransferase. This enzymes involvement in L. infantum virulence and survival underscores its potential as a drug target. Our search for selective inhibitors of LiSIR2RP1 has led, for the first time, to the identification of the antiparasitic and anticancer bisnaphthalimidopropyl (BNIP) alkyl di‐ and triamines (IC50 values in the single‐digit micromolar range for the most potent compounds). Structure–activity studies were conducted with 12 BNIP derivatives that differ in the length of the central alkyl chain, which links the two naphthalimidopropyl moieties. The most active and selective compound is the BNIP diaminononane (BNIPDanon), with IC50 values of 5.7 and 97.4 μM against the parasite and human forms (SIRT1) of the enzyme, respectively. Furthermore, this compound is an NAD+‐competitive inhibitor that interacts differently with the parasite and human enzymes, as determined by docking analysis, which might explain its selectivity toward the parasitic enzyme.

In Vitro and In Vivo Antimalarial Activity Assays of Seeds from Balanites aegyptiaca: Compounds of the Extract Show Growth Inhibition and Activity against Plasmodial Aminopeptidase.

Balanites aegyptiaca (Balanitaceae) is a widely grown desert plant with multiuse potential. In the present paper, a crude extract from B. aegyptiaca seeds equivalent to a ratio of 1 : 2000 seeds to the extract was screened for antiplasmodial activity. The determined IC50 value for the chloroquine-susceptible Plasmodium falciparum NF54 strain was 68.26 μg/μL ± 3.5. Analysis of the extract by gas chromatography-mass spectrometry detected 6-phenyl-2(H)-1,2,4-triazin-5-one oxime, an inhibitor of the parasitic M18 Aspartyl Aminopeptidase as one of the compounds which is responsible for the in vitro antiplasmodial activity. The crude plant extract had a K i of 2.35 μg/μL and showed a dose-dependent response. After depletion of the compound, a significantly lower inhibition was determined with a K i of 4.8 μg/μL. Moreover, two phenolic compounds, that is, 2,6-di-tert-butyl-phenol and 2,4-di-tert-butyl-phenol, with determined IC50 values of 50.29 μM ± 3 and 47.82 μM ± 2.5, respectively, were detected. These compounds may contribute to the in vitro antimalarial activity due to their antioxidative properties. In an in vivo experiment, treatment of BALB/c mice with the aqueous Balanite extract did not lead to eradication of the parasites, although a reduced parasitemia at day 12 p.i. was observed.

Synthesis, cytotoxicity and DNA-binding of novel bisnaphthalimidopropyl derivatives in breast cancer MDA-MB-231 cells

New naphthalimidopropyl, bisphthalimidopropyl and bisnaphthalimidopropyl (BNIP) derivatives were synthesised and characterised. Their interactions with Calf Thymus DNA were studied by UV spectrophotometric analysis and a competitive Ethidium bromide displacement assay. Cytotoxicity was determined by MTT assay in a breast cell system (MDA-MB-231 and MCF-10A cells). All BNIPs exhibited strong DNA-binding properties and cytotoxic activity with IC(50) values in the range of 0.83-12.68 microM (24 and 48 h treatment). In addition, the uptake of BNIP derivatives within cancer cells was not via utilisation of the MGBG polyamine transporter. Put together the results confirm that the presence of the bisnaphthalimidopropyl and alkyl linker functionality are crucial for exerting DNA-binding and cytotoxic properties, hence demonstrating promise in their further development as potential anti cancer agents.

Characterization and evaluation of BNIPDaoct- loaded PLGA nanoparticles for visceral leishmaniasis: in vitro and in vivo studies

OBJECTIVE To overcome the limitation of bisnaphthalimidopropyldiaaminooctane (BNIPDaoct) low physiological solubility and potentially increase its efficiency against visceral leishmaniasis (VL), a delivery system based on poly(d,l-lactide-co-glycolide) (PLGA) nanoparticles was developed. MATERIALS & METHODS BNIPDaoct-PLGA nanoparticles were prepared by nanoprecipitation and characterized. Anti-Leishmania activity was evaluated using in vitro and in vivo VL infection models. RESULTS BNIPDaoct-PLGA nanoparticles were successfully produced and were sized at 156.0 ± 2.8 nm with an encapsulation efficiency of approximately 85%. The PLGA nanoparticles reduced BNIPDaoct cellular toxicity, retained its in vitro anti-leishmanial activity and led to a significant reduction (∼80%) in the parasite burden in the infected mice spleen when compared with the free drug or amphotericin B. In the liver the effect was less pronounced, with a 30-50% reduction observed between the nanoformulation and the BNIPDaoct per se or the amphotericin B, respectively. CONCLUSION PLGA nanoparticles provide controlled and effective delivery of BNIPDaoct for treatment of VL.

In vitro evaluation of bisnaphthalimidopropyl derivatives loaded into pegylated nanoparticles against Leishmania infantum protozoa.

Bisnaphthalimidopropyl (BNIP) derivatives have recently been shown to have potential as antileishmanial agents. However, these compounds have some drawbacks, including their low aqueous solubility and some toxic effects. In this study, we designed a drug delivery system for enhanced delivery of BNIP derivative compounds whilst reducing adverse toxic effects, and hence increasing their biological efficacy. A coated drug delivery system based on polymeric nanoparticles of pegylated poly(lactic acid) (PLA), a biodegradable polymer, was successfully achieved. The pegylated PLA nanoformulations loaded with BNIP derivatives were evaluated in an in vitro model of intracellular amastigotes in murine J774 and human THP-1 cells for visceral leishmaniasis using luciferase-expressing Leishmania infantum parasites. Pegylation of PLA nanoparticles significantly reduced the capacity of empty nanoparticles in inhibiting intracellular parasite growth. The BNIP derivatives BNIPDadec and BNIPDaoct exhibited EC(50) values (concentration of compound necessary to decrease cell viability to 50% of the untreated control) of ca. 4.5 μM for THP-1 and J774 cells and ca. 9.0 μM for mouse bone marrow-derived macrophages. Nanoparticle encapsulation of the BNIP derivative compounds decreased their toxicity towards macrophages by ≥10-fold as evaluated by the MTT assay. The antileishmanial activity of free BNIPDadec was 1.02±0.41 μM and 0.73±0.06 μM for THP-1 and J774 macrophages, respectively. Pegylation of PLA nanoparticles loaded with BNIPDadec resulted in EC(50) values of 1.43±0.63 μM and 1.79±0.77 μM for THP-1 and J774 macrophages, respectively. A similar trend was observed for free BNIPDaoct and pegylated BNIPDaoct PLA nanoparticles (2.43±0.19 μM and 1.23±0.40 μM for THP-1 macrophages and 1.36±0.17 μM and 1.52±0.57 μM for J774 macrophages). The nanoformulations were more efficient in reducing parasitic growth inside human macrophages than in murine cells, suggesting host cell-dependent metabolism.

Bisnaphthalimidopropyl spermidine induces apoptosis within colon carcinoma cells.

Bisnaphthalimido compounds bisintercalate to DNA via the major groove and are potentially potent cancer therapeutics. We incorporated natural polyamines as linkers connecting the two-naphthalimido ring moieties to create a series of novel soluble cytotoxic bisnaphthalimidopropyl polyamines (BNIPPs). Here, we determined the cytotoxicity of bisnaphthalimidopropyl spermidine (BNIPSpd) towards Caco-2 and HT-29 colon adenocarcinoma cells revealing an IC(50) value of 0.15 and 1.64 microM after 48h exposure within Caco-2 and HT-29 cells, respectively. After 4h, >/=0.5 microM BNIPSpd treatment-induced significant DNA damage. After 24h exposure a concentration-dependent increase in active caspase-3 expression, chromatin condensation and internucleosomal DNA fragmentation identified apoptosis as the principal manifestation for the cytotoxicity within both cell lines. By 24h exposure, there was also a significant decline in cellular spermine and spermidine levels. It is concluded that bisnaphthalimidopropyl spermidine (BNIPSpd) toxicity primarily results from apoptosis and that BNISpd has potential to be further developed as an anti-tumour agent.

Synthesis of novel oxa-isosteres of spermidine and spermine

Abstract 3-Bromopropylamine hydrobromide reacts with N -hydroxyphthalimide in the presence of DBU to give, not the expected N -(3-aminopropyloxy)phthalimide, but N -(3-aminooxypropyl)-phthalimide, 6 , formed by an unusual intramolecular rearrangement. Coupling of the pentamethyl-chroman-6-sulphonyl (Pmc) derivatives of 9 and 13 with N -Bpoc-aminopropanol affords a differentially protected 6-oxaspermidine 10 and 6,9-dioxaspermine 14 respectively from which the protecting groups are removed independently.

Base pairing of cytosine analogues with adenine and guanine in oligonucleotide duplexes: evidence for exchange between Watson–Crick and wobble base pairs using 1H NMR spectroscopy

1 H NMR spectra of oligodeoxynucleotide duplexes incorporating N4-methoxycytosine and a related analogue paired with adenine and guanine demonstrate that Watson–Crick and wobble base pairs are in slow exchange on the chemical shift timescale.