Free radical scavenging reactions and antioxidant activities of silybin: mechanistic aspects and pulse radiolytic studies.
Silybin (extracted from Silybum marianum) is the major active constituent of silymarin which possesses a wide range of medicinal properties. These properties may be, in part, due to the potent scavenging capacity of oxidizing free radicals. In this context, scavenging radicals (hydroxyl, azide, dibromide anion radicals, nitrite, carbonate, etc.) of silybin have been studied to understand the mechanistic aspects of its action against free radicals. The transients produced in these reactions have been assigned and the rate constants have been measured by pulse radiolysis techniques. Reduction potential determined both by cyclic voltammetry gave a value 0.62+/-0.02 V vs NHE at pH 9. Quantum chemical calculations have been performed to further confirm the different activities of individual hydroxyl groups with the difference of heat of formation. Moreover, silybin also protected plasmid pUC18 DNA from soft X-ray radiation which induced strand breaks. These results are expected to be helpful for a better understanding of the anti-oxidative properties of silybin.
Fu
Haiying
H
Radiation Chemistry and Technology Laboratory, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, PR China. tf.erine2008@gmail.com
Lin
Mingzhang
M
Muroya
Yusa
Y
Hata
Kuniki
K
Katsumura
Yosuke
Y
Yokoya
Akinari
A
Shikazono
Naoya
N
Hatano
Yoshihiko
Y
D000975:Antioxidants / Q000737:chemistry* / Q000494:pharmacology; D001386:Azides / Q000737:chemistry; D001965:Bromides / Q000737:chemistry; D002254:Carbonates / Q000737:chemistry; D053904:DNA Breaks, Single-Stranded; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000494:pharmacology; D005609:Free Radicals / Q000737:chemistry*; D017665:Hydroxyl Radical / Q000737:chemistry; D008956:Models, Chemical; D009585:Nitrogen Dioxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010545:Peroxides / Q000737:chemistry; D010957:Plasmids / Q000187:drug effects / Q000528:radiation effects; D011675:Pulse Radiolysis; D000077385:Silybin; D012838:Silymarin / Q000737:chemistry / Q000494:pharmacology; D013431:Sulfates / Q000737:chemistry
D000975:Antioxidants; D001386:Azides; D001965:Bromides; D002254:Carbonates; D016166:Free Radical Scavengers; D005609:Free Radicals; D010545:Peroxides; D012838:Silymarin; D013431:Sulfates; C069025:sulfate radical; D017665:Hydroxyl Radical; D000077385:Silybin; C029952:trichloromethylperoxy radical; D009585:Nitrogen Dioxide