タモギタケから単離したエルゴチオネインの加熱および各pHにおける抗酸化性への影響

エルゴチオネインの抗酸化性について加熱温度および各pHの影響をORAC分析法で調べた。1) タモギタケから得た精製エルゴチオネインは、ORAC法においてグルタチオン、L-システイン、L-メチオニンなどのチオール基含有アミノ酸および含硫アミノ酸と比べ抗酸化活性が高かった。DPPHラジカル消去活性評価法による測定においても同様の結果を示した。2) 精製したエルゴチオネインおよびエルゴチオネインを含む抽出物は、加熱温度や各pHで抗酸化性が変わらず、安定的に抗酸化能を有する化合物であることが、ORAC法において確認された。We investigated the effects of heat and pH on the antioxidative activity of ergothioneine from Pleurotus cornucopiae using Oxygen Radical Absorbance Capacity (ORAC) and DPPH radical scavenging activity methods. The ORAC assayed showed that ergothioneine maintained high antioxidative activity at 25, 40, 60, 80, and 100℃. Proportional decreases in the antioxidative activity of L-ascorbic acid and garlic acid were observed with increases in temperature. L-ascorbic acid, in particular, showed a large reduction in ORAC value, with the antioxidative activity at 100℃ only 23% that at 25℃. Ergothioneine and garlic acid showed high antioxidative activity for 7 days under acidic or neutral conditions (pH 3.0, pH 5.0, and pH 7.0). Furthermore, ergothioneine maintained its antioxidative activity for 7 days under neutral and alkali conditions (pH 7.2 and pH 9.0), whereas that of garlic acid decreased to about 70% at day 3. The antioxidative activity of L-ascorbic acid decreased at every pH as time increased. From these results, it appears that ergothioneine is an excellent antioxidant on which heat and pH have little effect. Further, we found that ergothioneine has the highest level of antioxidative activity of the four amino acids tested (ergothioneine, glutathione, L-methionine and L-cysteine)