Takebayashi Jun, Asano Ryuji, Nakae Yoshinori, Saito Morio, Gohda Eiichi, Yamamoto Itaru, Tai Akihiro
Department of Immunochemistry, Division of Pharmaceutical Sciences, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan.
Biosci Biotechnol Biochem. 2007 Mar;71(3):754-60. doi: 10.1271/bbb.60602. Epub 2007 Mar 7.
The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging mechanism of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) was studied. We found two undefined products, named X and Y, in the reaction mixture of AA-2G and the DPPH radical under acidic conditions by HPLC analysis. The reaction mixture was further subjected to LC-MS analysis. X was found to be a covalent adduct of AA-2G and the DPPH radical. On the other hand, Y could not be identified, probably because it was a mixture. A time-course study of the radical-scavenging reaction revealed that one molecule of AA-2G scavenged one molecule of DPPH radical to generate an AA-2G radical, which readily reacted with another molecule of the DPPH radical to form a covalent adduct (X). Subsequently, this adduct slowly quenched a third molecule of the DPPH radical, resulting in reaction products (Y). Therefore, one molecule of AA-2G has only one oxidizable -OH group, but can scavenge three molecules of the DPPH radical. The radical-scavenging mechanism of AA-2G elucidated in this study should be useful in understanding the biological roles of AA-2G per se in the food and cosmetic fields.
研究了2-O-α-D-吡喃葡萄糖基-L-抗坏血酸（AA-2G）的1,1-二苯基-2-苦基肼基（DPPH）自由基清除机制。通过高效液相色谱（HPLC）分析，我们在酸性条件下AA-2G与DPPH自由基的反应混合物中发现了两种未明确的产物，命名为X和Y。对该反应混合物进一步进行液相色谱-质谱（LC-MS）分析。发现X是AA-2G与DPPH自由基的共价加合物。另一方面，Y无法鉴定，可能是因为它是一种混合物。自由基清除反应的时间进程研究表明，一分子AA-2G清除一分子DPPH自由基生成一个AA-2G自由基，该自由基很容易与另一分子DPPH自由基反应形成共价加合物（X）。随后，该加合物缓慢淬灭第三分子DPPH自由基，生成反应产物（Y）。因此，一分子AA-2G只有一个可氧化的-OH基团，但能清除三分子DPPH自由基。本研究阐明的AA-2G自由基清除机制，对于理解AA-2G本身在食品和化妆品领域的生物学作用应该是有用的。
