Redox Properties of Mn(III)porphyrins in Hyaluronan Oxidative Degradation: Single Electron Transfer Mechanism.

Cationic Mn(III)-meso-tetraarylporphyrin derivatives, substituted in para position with different size alkyl chains, were investigated to function as antioxidants in free-radical degradation of high-molar-mass hyaluronan by the methods of rotational viscometry and oximetry. The results of rotational viscometry showed that MnTM-4-PyP5+, MnTE-4-PyP5+, MnTPr-4-PyP5+, MnTPen-4-PyP5+ and MnTHep-4-PyP5+ showed high efficiency in decomposing H2O2, and reducing of peroxidized hyaluronan. When using oxygen electrode, MnTE-4-PyP5+, MnTPr-4-PyP5+, MnTPen-4-PyP5+, and MnTHep-4-PyP5+ applied to function as protective antioxidants in hyaluronan degradation, the uptake of dissolved oxygen from the reaction milieu was rapid, followed by continual increase in oxygen concentration up to the end of the measurement. However, when especially MnTE-4-PyP5+, MnTPr-4-PyP5+, and MnTPen-4-PyP5+ were examined as hyaluronan chain-breaking antioxidants, after short-term dissolved oxygen uptake, almost no increase in oxygen concentration was shown.

Preparation and Physicochemical Characterization of Gelatin-Aldehyde Derivatives.

The present study aimed at preparing novel free-radical scavenging and water-soluble compounds derived from gelatin. Specifically, gelatin−syringaldehyde, gelatin−anisaldehyde, and gelatin−vanillin were synthesized and thoroughly studied for their physicochemical properties. In particular, the compounds were characterized by UV-Vis spectroscopy, Fourier-transform infrared spectroscopy, and scanning electron microscopy. Notably, as demonstrated by thermogravimetry and differential scanning calorimetry, all three derivatives exhibited higher thermal stability than gelatin itself. Free-radical scavenging activities of the examined compounds were explored by (i) a standard spectrophotometric ABTS assay and (ii) an assay of oxidative degradation of hyaluronic acid monitored by rotational viscometry. We found that gelatin and gelatin−syringaldehyde demonstrated the highest efficacy in scavenging •OH radicals, whereas gelatin−anisaldehyde was the least effective. The efficacy of scavenging alkyloxy- and alkylperoxy-type free radicals via hydrogen-atom-transferring property was in the following order: gelatin > gelatin−vanillin > gelatin−syringaldehyde > gelatin−anisaldehyde. Electron-donor properties determined using the ABTS assay revealed the following order in one-electron reduction of ABTS•+: gelatin > gelatin−anisaldehyde > gelatin−vanillin > gelatin−syringaldehyde.

Oxidative Degradation of High-Molar-Mass Hyaluronan: Effects of Some Indole Derivatives to Hyaluronan Decay.

Indole derivatives such as isatin (a natural compound), cemtirestat, stobadine, and its derivatives (synthetic compounds) are known to have numerous positive effects on human health due to regulation of oxidative status. The aim of the study was to assess radical scavenging capacities of these compounds and explore their potential protective effects against reactive oxygen species formed during Cu(II) ions and ascorbate-induced degradation of high-molar-mass hyaluronan. Based on the IC50 values determined by the ABTS assay, the most effective compound was SM1M3EC2·HCl reaching the value ≈ 11 µmol/L. The lowest IC50 value reached in the DPPH assay was reported for cemtirestat ≈ 3 µmol/L. Great potency of inhibition of hyaluronan degradation was shown by cemtirestat, followed by isatin even at low concentration 10 µmol/L. On the other hand, stobadine·2HCl had also a protective effect on hyaluronan degradation, however at greater concentrations compared to cemtirestat or isatin. SME1i-ProC2·HCl reported to be a less effective compound and SM1M3EC2·HCl can be considered almost ineffective compared to stobadine·2HCl. In conclusion, our results showed that both isatin and cemtirestat were capable of attenuating the degradation of high-molar-mass hyaluronan due to their ability to complex/sequester cupric ions.

Dynamic Viscosity of the NaF-KF-NdF3 Molten System.

The dynamic viscosity (η) of the molten system (NaF-KF)eut-NdF3 containing NdF3 in an amount from 0 to 15 mol.% was studied by rotational viscometry using a high-temperature rheometer, FRS 1600. Viscosity measurements were carried out in the temperature range from liquidus to 1153 K. The measurement procedure was tested on the (LiF-NaF-KF)eut melt. The choice of the parameter shear rate was carried out according to the viscosity and flow curves. Viscosity does not depend on shear rate, and therefore the investigated melts behave like Newtonian fluids, in the range of 9-19 s-1. The experimentally obtained viscosity values for (NaF-KF)eut-NdF3 melts in a wide temperature range are described by an exponential equation. In the coordinates ln(η) = f(1/T), they are straight lines; however, their temperature coefficients are noticeably different, which indicates significant impacts of composition and temperature.

Impact of Ergothioneine, Hercynine, and Histidine on Oxidative Degradation of Hyaluronan and Wound Healing.

A high-molecular weight hyaluronan is oxidatively degraded by Cu(II) ions and ascorbate-the so called Weissberger biogenic oxidative system-which is one of the most potent generators of reactive oxygen species, namely •OH radicals. Ergothioneine, hercynine, or histidine were loaded into chitosan/hyaluronan composite membranes to examine their effect on skin wound healing in ischemic rabbits. We also explored the ability of ergothioneine, hercynine, or histidine to inhibit hyaluronan degradation. Rotational viscometry showed that ergothioneine decreased the degree of hyaluronan radical degradation in a dose-dependent manner. While histidine was shown to be potent in scavenging •OH radicals, however, hercynine was ineffective. In vivo results showed that the addition of each investigated agent to chitosan/hyaluronan membranes contributed to a more potent treatment of ischemic skin wounds in rabbits compared to untreated animals and animals treated only with chitosan/hyaluronan membranes.

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.