Two new antimicrobial dimeric compounds: febrifuquinone, a vismione-anthraquinone coupled pigment and adamabianthrone, from two Psorospermum species

Febrifuquinone (1), a new vismione-anthraquinone coupled pigment and a new bianthrone named adamabianthrone (2), were isolated respectively, from the roots of Psorospermum febrifugum and from the bark of Psorospermum adamauense along with eight known compounds including: two bianthrones [(bianthrone A(1) (3) and bianthrone A(2b)], one vismione [(vismione D (4)], one anthrone (3-geranyloxyemodin anthrone) and four anthraquinones [(1,8-dihydroxy-3-isoprenyloxy-6-methylanthraquinone, emodin (5), 3-geranyloxy-1,8-dihydroxy-6-methylanthraquinone and 2-geranyl-1,8-dihydroxy-6-methylanthraquinone]. Their structures were determined using modern spectroscopic methods including one and two dimensional-NMR techniques as well as MS. Compounds 1 and 2 showed significant antimicrobial activities against a wide range of bacteria and fungi.

Syntheses of methyl (4,6-dideoxy-alpha-L-lyxo-hexopyranosyl)-(1-->3)- and (4-deoxy-4-fluoro-alpha-L-rhamnopyranosyl)-(1-->3)- 2-acetamido-2-deoxy-alpha-D-glucopyranosides, analogs of the mycobacterial arabinogalactan linkage disaccharide

We have made thioglycoside donors for the 4,6-dideoxy-L-lyxo-hexopyranosyl ('4-deoxy-L-rhamnosyl') and 4-deoxy-4-fluoro-L-rhamnosyl monosaccharide residues. The preparation of the deoxyfluororhamnose was not straightforward, and revealed some unexpected behavior of the diethylaminosulfur trifluoride (DAST) reagent. The new glycosyl donors were used to synthesize two analogs of the mycobacterial arabinogalactan linkage disaccharide -->4)-alpha-L-Rha-(1-->3)-alpha-D-GlcNAc. These analogs are prototypes for a family of potential inhibitors of the enzymes involved in the early stages of cell-wall construction in mycobacteria.

Chemoenzymatic synthesis of a trimeric ganglioside GM3 analogue

A trimeric beta-lactosyl cluster based on 2-nitro-2-(hydroxymethyl)propane-1,3-diol was prepared using the trichloroacetimidate method. Kinetic studies showed that this cluster was an effective acceptor for rat-liver alpha-(2-->3)-sialyltransferase. Its KM was comparable to those for monomeric lactose and N-acetyllactosamine acceptors, and its Vmax was 1% of that measured for the LacNAc acceptor. Preparative-scale sialylation using this enzyme afforded a trimeric cluster of the ganglioside GM3 oligosaccharide in good yield. The NMR spectra of the trimeric GM3 analogue suggest that the oligosaccharide conformation is not significantly perturbed by this level of clustering.

Effect of poly(vinylsulfonate) on murine AA amyloid: a high-resolution ultrastructural study

In experimental murine inflammation-associated amyloidosis (AA amyloidosis), an interaction between heparan sulfate and serum amyloid A (SAA), the AA precursor, has been demonstrated and is believed to play an important role in AA amyloidogenesis. Poly(vinylsulfonate) sodium salt (PVS) can arrest AA amyloid induction and cause established amyloid deposits to regress. PVS is thought to have this property by virtue of limited anionic structural similarities it has to heparan sulfate. In the present study, a comparison has been made of the in situ light microscopic and high-resolution ultrastructure of amyloid deposits before and after PVS treatment. As shown recently in situ, AA fibrils from untreated mice are composed of an outer layer of heparan sulfate proteoglycan and a 1- to 2-nm filament network of AA protein. This layer encloses a microfibril-like structure composed of chondroitin sulfate proteoglycan wound around a core of amyloid P component. After treatment with PVS, both the heparan sulfate proteoglycan and the AA filament network are lost from the fibrils, and the more central portion disintegrates into the chondroitin sulfate proteoglycan with associated amyloid P subunits. These findings add further support to the concept that heparan sulfate proteoglycan is important in amyloid fibril structure, and interference with its binding interactions with the amyloid filament protein provides a point of therapeutic attack.

Arresting amyloidosis in vivo using small-molecule anionic sulphonates or sulphates: implications for Alzheimer's disease

Amyloid is a term for extracellular protein fibril deposits that have characteristic tinctorial and structural properties. Heparan sulphate, or the heparan sulphate proteoglycan perlecan, has been identified in all amyloids and implicated in the earliest stages of inflammation-associated (AA) amyloid induction. Heparan sulphate interacts with the AA amyloid precursor and the beta-peptide of Alzheimer's amyloid, imparting characteristic secondary and tertiary amyloid structural features. These observations suggest that molecules that interfere with this interaction may prevent or arrest amyloidogenesis. We synthesized low-molecular-weight (135-1,000) anionic sulphonate or sulphate compounds. When administered orally, these compounds substantially reduced murine splenic AA amyloid progression. They also interfered with heparan sulphate-stimulated beta-peptide fibril aggregation in vitro.