Influence of tiopronin, captopril and levamisole therapeutics on the oxidative degradation of hyaluronan.

The ability to protect hyaluronic acid (HA) from oxidative degradation by cupric ions and ascorbate (production of (•)OH and peroxy-type radicals) during acute phase joint inflammation has been investigated using the following drugs: tiopronin, captopril, and levamisole. Radical scavenging activity, i.e. the propensity for donation of electrons was assessed for the drugs by ABTS and DPPH assays. The kinetics of HA degradation have been measured in the presence of each drug using rotational viscometry. The results of ABTS and DPPH assays show the highest radical scavenging activity for captopril, followed by tiopronin. For levamisole, no effect was observed. Captopril and tiopronin prevented HA degradation induced by (•)OH radicals in a similar manner, while tiopronin was more effective in scavenging peroxy-type radicals. On the other hand, levamisole was shown to be a pro-oxidant. Recovered HA fragments were characterized using FT-IR analysis, the incorporation of a sulphur atom from captopril and tiopronin but not from levamisole into the HA molecule was demonstrated.

Synthesis, design and biological evaluation of novel highly potent tacrine congeners for the treatment of Alzheimer's disease.

New tacrine derivatives 5a-d, 6a-d with piperazino-ethyl spacer linked with corresponding secondary amines and tacrine homodimer 8 were synthesized and tested as cholinesterase inhibitors on human acetylcholinesterase (hAChE) and human plasmatic butyrylcholinesterase (hBChE). In most cases the majority of synthesized derivatives exhibit a high AChE and BChE inhibitory activity with IC(50) values in the low-nanomolar range, being clearly more potent than the reference standard tacrine (9-amino-1,2,3,4-tetrahydroacridine, 1) and 7-MEOTA (7-methoxy-9-amino-1,2,3,4-tetrahydroacridine). Among them, inhibitors 8 and 5c, showed a strong inhibitory activity against hAChE, with an IC(50) value of 4.49 nM and 4.97, nM resp., and a high selectivity to hAChE. The compound 5d acted as the most potent inhibitor against hBChE with an IC(50) value of 33.7 nM and exhibited also a good selectivity towards hBChE. The dissociation constants K(i) of the selected inhibitors were compared with their IC(50) values. Molecular modeling studies were performed to predict the binding modes between individual derivatives and hAChE/hBChE.

Free-radical degradation of high-molar-mass hyaluronan induced by ascorbate plus cupric ions: testing of stobadine and its two derivatives in function as antioxidants.

Stobadine·2HCl and its two hydrophilic derivatives SM1dM9dM10·2HCl and SME1i-ProC2·HCl were tested in the function of antioxidants on hyaluronan (HA) degradation induced by the Weissberger oxidative system [ascorbate plus Cu(II)]. As a primary method, rotational viscometry was applied, where the substance tested was added before or 1 h after the initiation of HA degradation. The most effective scavengers of •OH and peroxy-type radicals were recorded to be stobadine·2HCl and SME1i-ProC2·HCl, respectively. The most effective scavenger, determined by applying the ABTS assay, was stobadine·2HCl.

Free-radical degradation of high-molar-mass hyaluronan induced by Weissberger's oxidative system: potential antioxidative effect of bucillamine.

OBJECTIVES: Hyaluronan (HA), one of the main components of extracellular matrix, is a glycosaminoglycan composed of repeating disaccharide units of N-acetyl-d-glucosamine and d-glucuronic acid linked by ß-(1→4) and ß-(1→3) glycoside bonds. High-molar-mass HA was used as a model for studying its oxidative degradation. In the present paper protective effects of bucillamine against the free-radical degradation of HA were investigated. The HA fragments generated were characterized as well. METHODS: To induce free-radical-mediated degradation of high-molar-mass HA under aerobic conditions, we applied Weissberger's oxidative system, comprising biogenic compounds in relevant pathophysiological concentrations, i.e. 100 µM ascorbate plus 1 µM Cu(II). Time-dependent decreases of dynamic viscosity of the HA solutions were recorded by rotational viscometry. Electron donor behaviors of bucillamine were studied by a standard ABTS test method and a chemiluminescence (CL) assay. Ability of incorporation of generated bucillamine thiyl radicals into the biopolymer was verified by Fourier-transform infrared spectroscopy (FT-IR) and size exclusion chromatography with a multi-angle light scattering photometer (SEC-MALS). RESULTS: Decrease of HA viscosity reflected HA degradation. The drug tested was applied in two arrangements: to prevent •OH radical generation (1) and ROO• type radicals propagation (2). Bucillamine, which acted as an efficient •H donor, is also a proper electron donor, as proved by ABTS and CL assays. FT-IR and SEC-MALS methods showed that the drug tested did not incorporate into the biopolymer chains. CONCLUSION: Bucillamine significantly protected high-molar-mass HA against free-radical degradation in vitro, and supposedly this positive action of the drug may be involved in its beneficial effect observed in clinical practice.

Free-radical degradation of high-molecular-weight hyaluronan induced by ascorbate plus cupric ions. Testing of bucillamine and its SA981-metabolite as antioxidants.

High-molecular-weight hyaluronan (HA) samples were exposed to free-radical chain-degradation reactions induced by ascorbate in the presence of Cu(II) ions - the so-called Weissberger's oxidative system. The concentrations of both reactants [ascorbate, Cu(II)] were comparable to those that may occur during an early stage of the acute phase of joint inflammation. The time-dependent changes of the viscosity of the HA solution in the absence of the substance tested were monitored by rotational viscometry. However, when the anti- or pro-oxidative effects of the antioxidants/drugs were investigated, their dose-dependency was also examined. Additionally, the anti-oxidative activities of these substances were screened by the well-established ABTS and DPPH decolorization assays. The actions of the disease-modifying anti-rheumatic drugs, namely bucillamine and D-penicillamine, were compared to those of L-cysteine and of SA981, the oxidized metabolite of bucillamine. The results indicated that bucillamine was the most efficient scavenger of hydroxyl- and/or peroxyl-type radicals, even at the lowest drug concentration. In contrast, SA981 demonstrated no scavenging activity against the aforementioned free radicals. D-Penicillamine and L-cysteine showed a dual effect, i.e. a pronounced anti-oxidative effect was, after a given time period, followed by a significant pro-oxidative effect.