Chemical Modification of Ginsenoside on Cell Viability and Cytokine Secretion.

BACKGROUND: Rb1 is a ginsenoside steroid glycoside found exclusively in the plant Panax ginseng. In an earlier report, we showed that Rb1 increased cell proliferation and reduced VEGF (vascular endothelial growth factor) secretion by human retinal pigment epithelial (ARPE19) cells. OBJECTIVE: In the present study, we hypothesized that chemical modification of Rb1 changes the level of VEGF secretion by ARPE19 cells. METHOD: Three derivatives of Rb1 were chemically synthesized by hydrogenation (Rb1-H2), acetylation (Rb1-Acyl), and epoxidation (Rb1-Epoxy). Structural modifications were confirmed by 1H Nuclear Magnetic Resonance (NMR) spectra and Mass Spectrometry (MS). To test the biological activity, chemically modified compounds were added to cell culture media and incubated for 72 hours at a concentration of 250 nM at 37°C. Conditioned media were collected and cells were harvested/ counted after treatment. Viable cell numbers were determined by the trypan blue dye exclusion method and VEGF levels by Enzyme-Linked Immunosorbent Assays (ELISA). RESULTS: Consistent with the prior report, results of the present study show Rb1 increased cell proliferation and decreased VEGF secretion. Similar to Rb1's effect on cell proliferation, treatment with Rb1-H2, Rb1-Acyl and Rb1-Epoxy resulted in an increase in cell numbers. In contrast to Rb1- induced decrease in VEGF secretion, treatment with Rb1-H2, Rb-Acyl and Rb1-Epoxy resulted in increased VEGF levels. CONCLUSION: Chemical modifications of the ginsenoside Rb1 significantly affect the biological activity of VEGF secretion by ARPE19 cells. Additional SAR (Structure Activity Relationship) experiments will be conducted to study the detailed mechanisms by which how specific modifications of Rb1 functional groups alter biological activities.

Human serum albumin as vehicle for the solubilization of perylene diimides in aqueous solutions.

The chemical, physical and photophysical properties of perylene diimides have attracted substantial attention for the potential applications in diverse fields ranging from advanced materials to biomedical applications. Some applications require the diimides to be in aqueous environment where they tend to dissolve poorly. We investigated the use of human serum albumin as a vehicle to increase the aqueous exposure of monomeric perylene diimides. Since studies on the interactions of these compounds with protein is scarce we characterized the binding and the possible effects on the protein. In order to increase the affinity of the dyes to the protein we have used perylene diimides with substituents that replicate the side chains of natural amino acids. The results show that only the dyes containing the side chain of leucine and phenylalanine yield measurable binding. Only the phenylalanine analogue promotes energy transfer with the lone tryptophan residue of albumin indicating different binding modalities for the dyes. In addition, this analogue is the only one which shows photochemical activity that prompts its release from the protein upon laser irradiation.

Self-Assembled Nanospheres for Encapsulation and Aerosolization of Rifampicin.

Rifampicin (RIF) is a benchmark drug for treatment of tuberculosis, but poor bioavailability, prolonged treatment, and pill burden have been linked to therapeutic failure and the development of multidrug resistant strains. To overcome these limitations, this study investigated a method of rifampicin nanoencapsulation and aerosol delivery using a commercial, hand-held nebulizer modified with a nitrogen stream.

Characterization of novel perylene diimides containing aromatic amino acid side chains.

Perylene diimide derivatives have attracted initial interest as industrial dyes. Recently, much attention has been focused on their strong π-π stacks resulting from the large PDI aromatic core. These PDI stacks have distinct optical properties, and provide informative models that could mimic light-harvesting systems and initial charge transfer typical of photosynthetic systems. The absorption property of PDI derivatives may be tuned from visible to near-infrared region by peripheral substitution. We have studied a new class of PDI derivatives with aryl substituents derived from the side chains of aromatic aminoacids (Tyrosine, Tryptophan and Phenylalanine). We have investigated their absorption and the fluorescence properties in a set of organic solvents and established their different tendencies to aggregate in solution despite their solubility. Most aggregation appears to be unordered. One PDI analogue (the one formed from Tyr) in Methanol, however, appears to form J-type aggregates. Based on our results the compounds appear to be promising for future investigations regarding the interaction of these dyes with biomolecules.

Acid-responsive nanospheres from an asparagine-derived amphiphile.

We describe the synthesis and self-assembly of an asparagine-derived amphiphile. The self-assembled systems formulated with the inclusion of cholesterol (0-50 mol%) show encapsulation for a hydrophobic model drug and rapidly disintegrate in response to mild acidic conditions.

Interaction of human serum albumin with novel 3,9-disubstituted perylenes.

Human serum albumin (HSA) has been used as a model for the binding of a number of different ligands, including polyaromatic hydrocarbons, to proteins. In this case we have investigated the interaction of HSA with a novel set of perylene derivatives. Di-substituted perylene analogues have been synthesized as potentially useful organic photovoltaic materials. Their photophysical properties may make them viable for fuel cell applications too. However, these molecules are poorly soluble especially in aqueous solvents. Binding to water-soluble proteins may provide a way to solubilize them. At the same time one can study whether the photophysical processes initiated by the irradiation of a perylene ligand can cause conformational changes to the host protein. With the present study we demonstrated that of the three perylene derivatives investigated only one, the dimethoxy analogue, has a significant affinity for HSA at a binding site near the bottom of the central cleft (in proximity of the Trp214 residue). The small affinity prevents any significant photoinduced changes to occur in the protein.

Novel asparagine-derived lipid enhances distearoylphosphatidylcholine bilayer resistance to acidic conditions.

A novel asparagine-derived lipid analogue (ALA(11,17)) bearing a tetrahydropyrimidinone headgroup and two fatty chains (11 and 17 indicate the lengths of linear alkyl groups) was synthesized in high yield and purity. The thin film hydration of formulations containing 5 mol % or greater ALA(11,17) in distearoylphosphatidylcholine (DSPC) generated multilamellar vesicles (MLVs) that remained unaggregated according to optical microscopy, while those formed from DSPC only were highly clustered. The MLVs were processed into unilamellar liposomes via extrusion and were characterized by dynamic light scattering (DLS), zeta potential, turbidity, and scanning electron microscopy (SEM) analysis. Results show that the presence of ALA(11,17) in DSPC liposomes significantly alters the morphology, colloidal stability, and retention of encapsulated materials in both acidic and neutral conditions. The ability of ALA(11,17)-hybrid liposomes to encapsulate and retain inclusions under neutral and acidic conditions (pH < 2) was demonstrated by calcein dequenching experiments. DLS and SEM confirmed that ALA(11,17)/DSPC liposomes remained intact under these conditions. The bilayer integrity observed under neutral and acidic conditions and the likely biocompatibility of these fatty amino acid analogues suggest that ALA(11,17) is a promising additive for modulating phosphatidylcholine lipid bilayer properties.

Adsorption of Proteins to Thin-Films of PDMS and Its Effect on the Adhesion of Human Endothelial Cells.

This paper describes a simple and inexpensive procedure to produce thin-films of poly(dimethylsiloxane). Such films were characterized by a variety of techniques (ellipsometry, nuclear magnetic resonance, atomic force microscopy, and goniometry) and used to investigate the adsorption kinetics of three model proteins (fibrinogen, collagen type-I, and bovine serum albumin) under different conditions. The information collected from the protein adsorption studies was then used to investigate the adhesion of human dermal microvascular endothelial cells. The results of these studies suggest that these films can be used to model the surface properties of microdevices fabricated with commercial PDMS. Moreover, the paper provides guidelines to efficiently attach cells in BioMEMS devices.

The photophysical Characterisation of Novel 3,9-Dialkyloxy- and Diacyloxyperylenes.

The fundamental photophysical properties of three symmetrically substituted 3,9-perylene analogues were examined in a diverse range of solvents. All three compounds exhibited solvent-dependent fluorescence quantum yield, which was lower than that of perylene or its diimides. Whilst the absence of a large excited state dipole moment suggests that there is no preferential charge accumulation in one side of the molecules, the data suggest that intramolecular electron transfer occurs and that such an event causes additional photochemical mechanisms in chlorinated compounds where the fluorescence quantum yield is lower than in all other solvents and the values of the fluorescence decay change significantly. The dyes could be an interesting new class of fluorescence tags for labeling biomolecules and as dyes for organic photovoltaic materials.

(2S,4S)-3-Acryloyl-6-oxo-2-phenyl-perhydro-pyrimidine-4-carboxylic acid.

In the title compound, C(14)H(14)N(2)O(4), the central six-membered ring adopts a twisted boat conformation with the phenyl substituent occupying an orthogonal position [dihedral angle = 86.88 (11)°]. In the crystal, mol-ecules are linked by carboxylic acid-carbonyl O-H⋯O and amide-carbonyl N-H⋯O hydrogen bonds, forming a three-dimensional network.

4,10-Diall-yloxy-1,2,3,6b,7,8,9,12b-octa-hydro-perylene.

In the title compound, C(26)H(28)O(2), the central atoms are coplanar, with the -CH(2)-CH(2)- links of the cyclo-hexene groups lying to either side of the plane and with the diall-yloxy residues twisted out of this plane [C-C-O-C torsion angles = 16.6 (3) and -13.9 (3)°]. In the crystal structure, mol-ecules are connected into chains propagating in [100] via C-H⋯π inter-actions.

Tandem Friedel-Crafts annulation to novel perylene analogues.

Novel dialkyloxy- and dihydroxyoctahydroperylenes are regioselectively available via a new tandem Friedel-Crafts alkylation of tetrahydronaphthalene precursors followed by oxidative aromatization. Heating of 5-alkyloxy-1-tetralol with p-toluenesulfonic acid in sulfolane gave the corresponding octahydroperylenes in moderate yields. Studies with Lewis acids and tetralin-1,5-diol in acetonitrile at room temperature provided the 4,10-dihydroxy analogue cleanly, albeit in reduced yields. Examples of these new series of perylene analogues were partially oxidized to the corresponding contiguously aromatic, anthracene core products or fully aromatized to 3,9-dialkyloxyperylenes in good yields.