The pharmacologically active dichloromethane extracts of dried woad leaves (Isatis tinctoria L.), and the methanol extracts of comparable fresh leaves of the same plants, were analyzed by LC-MSn. The fresh leaf metabolite profile revealed a complex pattern of indolic compounds. Besides the known indigo precursors, isatan A, isatan B and indican, seven previously unreported indole derivatives were characterized: acetylindican, malonylindican, two dioxindole glucosides, dioxindole malonylglucoside, 6-hydroxyindole-3-carboxylic acid 6-O-glucoside and 6-hydroxyindole-3-carboxylic acid glucose ester. The integration of 122 compounds in fresh leaves and of five selected compounds (indoxyl, isatin, indigo, indirubin, and tryptanthrin) in dried leaves, formed the input data for a stepwise modelling procedure generating five predictive linear models. The structure of the predictive models and a cross validation provide evidence that the models could predict well or moderately well the accumulation of the selected lipophilic compounds, and were simple enough to be used in a woad cultivation program. PLS regression models relating each of the five selected dry leaf indolics to the fresh leaf metabolome were then fitted in order to deduct potential precursors and mechanisms leading to the formation of these lipophilic indolics in drying woad leaves. The models suggested glucobrassicin, isatan A and isatan B as the main candidate precursors of these compounds, besides a minor contribution of other fresh leaf indolics, including malonylindican, actylindican and dioxindole malonylglucoside. Dioxindole malonylglucoside was identified here as isatan C. The models further suggested that the accumulation of phenylpropanoid antioxidants in woad leaves has a negative impact on the formation of indoxyl, isatin, indigo, indirubin and tryptanthrin.

中文翻译：

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干木叶中亲脂性吲哚生物碱产量的代谢标志物 (Isatis tinctoria L.)

用 LC-MSn 分析干木兰叶 (Isatis tinctoria L.) 的药理活性二氯甲烷提取物和相同植物的类似新鲜叶的甲醇提取物。新鲜叶代谢物谱揭示了吲哚化合物的复杂模式。除了已知的靛蓝前体，isatan A、isatan B 和 indican 之外，还表征了七种先前未报道的吲哚衍生物：乙酰基印地聚糖、丙二酰吲哚、两种二氧吲哚葡萄糖苷、二氧吲哚丙二酰葡萄糖苷、6-羟基吲哚-3-羧酸、6-O-葡萄糖苷和 6-羟基吲哚-3-羧酸葡萄糖酯。新鲜叶中的 122 种化合物和干叶中的 5 种选定化合物（吲哚酚、靛红、靛蓝、靛玉红和色氨酸）的整合形成了逐步建模程序的输入数据，生成了五个预测线性模型。预测模型的结构和交叉验证提供的证据表明，这些模型可以很好地或适度地预测所选亲脂性化合物的积累，并且足够简单，可以用于禾本科栽培计划。然后拟合将五种选定的干叶吲哚类化合物中的每一个与新鲜叶代谢组相关联的 PLS 回归模型，以推导出导致干燥禾叶中这些亲脂性吲哚类化合物形成的潜在前体和机制。该模型表明，除了少量的其他新鲜叶吲哚类化合物（包括丙二酰吲哚、actylindican 和二氧吲哚丙二酰葡萄糖苷）外，这些化合物的主要候选前体是甘蓝素、isatan A 和isatan B。二氧吲哚丙二酰葡萄糖苷在这里被鉴定为isatan C。