Murata K, Yamaoka M, Ichikawa A
J Nutr Sci Vitaminol (Tokyo). 1976 Aug;22 SUPPL:7-12. doi: 10.3177/jnsv.22.supplement_7.
It was observed, in vitro, that the water extract of the fermented-tea customarily chewed by Thai people has a similar thermostable thiamine-inactivating factor to that found in the water extract of fern. It was also observed that the percentage of thiamine disulfide formed from thiamine with some flavones, catechol, pyrogallol, caffeic acid, dihydroxyphenylalanine, and hemin is greater at pH 7.5 than at pH 7.0. With some flavonoids, such as quercetin, rutin, and 6,7,4'-trihydroxyisoflavone, and pyrogallol, hemin, catechol and caffeic acid at pH 7.5, around 30-100% of thiamine is changed into thiamine disulfide. Water extract of shiitake, okra, coffee, black tea and fukinoto have only weak activities of thermostable thiamine-inactivating factors as a large percentage of thiamine disulfide is formed from thiamine even at pH 7.0. 2-Methyl-4-amino-5-aminomethylpyrimidine was isolated from the reaction mixture of 1 g thiamine with 20 mg catechol (1:0.5 mole) at pH 7.0, 45 degrees C, and identified with the synthesized pyrimidine.
在体外观察到，泰国人习惯咀嚼的发酵茶的水提取物具有与蕨类植物水提取物中发现的类似的热稳定硫胺素失活因子。还观察到，在pH 7.5时，硫胺素与一些黄酮类化合物、儿茶酚、连苯三酚、咖啡酸、二羟基苯丙氨酸和血红素形成硫胺素二硫化物的百分比高于pH 7.0时。在pH 7.5时，对于一些黄酮类化合物，如槲皮素、芦丁和6,7,4'-三羟基异黄酮，以及连苯三酚、血红素、儿茶酚和咖啡酸，约30%-100%的硫胺素会转化为硫胺素二硫化物。香菇、秋葵、咖啡、红茶和蜂斗菜的水提取物仅具有较弱的热稳定硫胺素失活因子活性，因为即使在pH 7.0时，也有很大比例的硫胺素会形成硫胺素二硫化物。在pH 7.0、45℃条件下，从1 g硫胺素与20 mg儿茶酚（1:0.5摩尔）的反应混合物中分离出2-甲基-4-氨基-5-氨甲基嘧啶，并与合成的嘧啶进行了鉴定。
