Nishizaki Daisuke, Iwahashi Hideo
Department of Chemistry, Wakayama Medical University, Wakayama 641-0011, Japan.
Am J Chin Med. 2015;43(1):87-101. doi: 10.1142/S0192415X15500068. Epub 2015 Feb 2.
Sho-saiko-to is an herbal medicine that is known to have diverse pharmacological activities and has been used for the treatment of various infectious diseases. Here, we examined the effects of baicalin, a compound isolated from Sho-saiko-to, and the effects of the iron chelator quinolinic acid on the Fenton reaction. The control reaction mixture contained 0.1 M 5,5-dimethyl-1-pyrroline N-oxide (DMPO), 0.2 mM H 2 O 2, 0.2 mM FeSO 4( NH 4)2 SO 4, and 40 mM sodium phosphate buffer (pH 7.4). Upon the addition of 0.6 mM baicalin or quinolinic acid to the control reaction mixture, the ESR peak heights of DMPO/OH radical adducts were measured as 32% ± 1% (baicalin) and 166% ± 27% (quinolinic acid) of that of the control mixture. In order to clarify why baicalin and quinolinic acid exerted opposite effects on the formation of hydroxyl radicals, we measured oxygen consumption in the presence of either compound. Upon the addition of 0.6 mM baicalin (or quinolinic acid) to the control reaction mixture without DMPO and H 2 O 2, the relative oxygen consumption rates were found to be 449% ± 40% (baicalin) and 18% ± 9% (quinolinic acid) of that of the control mixture without DMPO and H 2 O 2, indicating that baicalin facilitated the transfer of electrons from Fe (2+) to dissolved oxygen. Thus, the great majority of Fe (2+) turned into Fe (3+), and the formation of hydroxyl radicals was subsequently inhibited in this reaction.
小柴胡汤是一种具有多种药理活性的草药，已被用于治疗各种传染病。在此，我们研究了从小柴胡汤中分离出的化合物黄芩苷以及铁螯合剂喹啉酸对芬顿反应的影响。对照反应混合物含有0.1M 5,5-二甲基-1-吡咯啉N-氧化物（DMPO）、0.2mM H₂O₂、0.2mM FeSO₄(NH₄)₂SO₄和40mM磷酸钠缓冲液（pH 7.4）。向对照反应混合物中加入0.6mM黄芩苷或喹啉酸后，DMPO/OH自由基加合物的电子自旋共振（ESR）峰高测量值分别为对照混合物的32%±1%（黄芩苷）和166%±27%（喹啉酸）。为了阐明黄芩苷和喹啉酸为何对羟基自由基的形成产生相反的影响，我们测量了在这两种化合物存在下的耗氧量。向不含DMPO和H₂O₂的对照反应混合物中加入0.6mM黄芩苷（或喹啉酸）后，发现相对耗氧率分别为不含DMPO和H₂O₂的对照混合物的449%±40%（黄芩苷）和18%±9%（喹啉酸），这表明黄芩苷促进了电子从Fe(²⁺)转移到溶解氧。因此，绝大多数Fe(²⁺)转化为Fe(³⁺)，随后该反应中羟基自由基的形成受到抑制。
