Baugh Steven F
Industrial Laboratories, 4045 Youngfield St, Wheat Ridge, CO 80033, USA.
J AOAC Int. 2005 Nov-Dec;88(6):1607-12.
St. John's wort products are commonly standardized to total naphthodianthrones and hyperforin. Determination of these marker compounds is complicated because of the photochemistry of the naphthodianthrones pseudohypericin and hypericin and the instability of hyperforin in solution. Protopseudohypericin and protohypericin have been identified as naturally occurring naphthodianthrones and, when exposed to light, they are converted into pseudohypericin and hypericin, respectively. However, exposure to light and the resulting naphthodianthrone free-radical reactions oxidize hyperforin. A mathematical relationship between the response of the proto compound and the resulting naphthodianthrone can be established by comparing the analytical response of the proto compound in a solution protected from light with the increase in the analytical response of naphthodianthrone in the same solution after exposure to light. By mathematically converting the proto compounds to their respective products, exposure to light can be avoided while still including proto compounds in a single assay. The method presented here details the reporting of all significant naphthodianthrones, including protopseudohypericin and protohypericin, without exposure to light. This approach includes the benefits of improved naphthodianthrone precision and protection of hyperforin from oxidation.
圣约翰草产品通常以总萘并二蒽酮和金丝桃素进行标准化。由于萘并二蒽酮假金丝桃素和金丝桃素的光化学性质以及金丝桃素在溶液中的不稳定性，这些标志性化合物的测定很复杂。原假金丝桃素和原金丝桃素已被鉴定为天然存在的萘并二蒽酮，当暴露于光下时，它们分别转化为假金丝桃素和金丝桃素。然而，暴露于光以及由此产生的萘并二蒽酮自由基反应会氧化金丝桃素。通过比较原化合物在避光溶液中的分析响应与同一溶液在暴露于光后萘并二蒽酮分析响应的增加，可以建立原化合物与所得萘并二蒽酮响应之间的数学关系。通过数学方法将原化合物转化为它们各自的产物，可以避免暴露于光，同时仍能在单一测定中包含原化合物。本文介绍的方法详细说明了在不暴露于光的情况下所有重要萘并二蒽酮（包括原假金丝桃素和原金丝桃素）的报告。这种方法具有提高萘并二蒽酮精度以及保护金丝桃素不被氧化的优点。
