Spent coffee ground (SCG) is the remaining residue produced after extraction of coffee, and it is considered a source of unextracted bioactive compounds. For this, in the latest years, the attention has been focused to innovative reuses that can exploit the potentiality of SCG. Unfortunately, the content of bioactive compounds has not been thoroughly studied yet, and the major of publication has investigated the caffeine and chlorogenic acids levels, total polyphenol contents, and total flavonoid content. Hence, these approaches have determined only an estimation of flavonoids and polyphenols content and lack on single polyphenols investigation. Therefore, the objective of the current work was to provide a deep characterization of bioactive compounds in SCG. For this purpose, a new analytical method for the quantification of 30 molecules, including caffeine, chlorogenic acids, phenolic acids, flavonoids, and secoiridoids, has been developed using high-performance liquid chromatography tandem mass spectrometry. Moreover, several extraction procedures, that is, liquid-solid extraction assisted and not by ultrasounds, testing diverse solvents, were evaluated. Liquid-solid extraction assisted by sonication, with water/ethanol (30/70, v/v), resulted the best in terms of total bioactive compounds, and, once validated, the new analytical method was applied to five different espresso SCG samples. Data showed that caffeine (means: 1193.886 ± 57.307 mg kg-1 ) and chlorogenic acids (means of total CQAs: 1705.656 ± 88.694 mg kg-1 ) were the most abundant compounds in all SCG samples followed by phenolic acids such as caffeic, ferulic, gallic, p-coumaric, syringic, trans-cinnamic, and vanillic acid. Moreover, some flavonoids, that is, rutin, cyanidin 3-glucoside, and quercetin, occurred in almost all samples. This work provided a deepened characterization of bioactive compounds in SCG and can contribute to develop new strategies of reuses.

中文翻译：

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一种通过 HPLC-MS/MS 同时定量废咖啡渣中 30 种生物活性化合物的分析方法。

废咖啡渣 (SCG) 是咖啡提取后产生的剩余残留物，被认为是未提取的生物活性化合物的来源。为此，最近几年，注意力集中在可以利用 SCG 潜力的创新再利用上。不幸的是，生物活性化合物的含量还没有得到彻底的研究，主要的出版物调查了咖啡因和绿原酸的含量、总多酚含量和总黄酮含量。因此，这些方法仅确定了对类黄酮和多酚含量的估计，而缺乏对单一多酚的研究。因此，当前工作的目标是提供 SCG 中生物活性化合物的深入表征。为此，一种用于量化 30 个分子的新分析方法，包括咖啡因、绿原酸、酚酸、类黄酮和类环烯醚萜，已使用高效液相色谱串联质谱法开发。此外，还评估了几种提取程序，即液-固提取辅助而不是超声波，测试不同的溶剂。水/乙醇 (30/70, v/v) 超声辅助的液固萃取在总生物活性化合物方面取得了最好的结果，并且经过验证后，新的分析方法被应用于五种不同的浓缩咖啡 SCG 样品。数据显示，咖啡因（平均值：1193.886 ± 57.307 mg kg-1 ）和绿原酸（总 CQAs 平均值：1705.656 ± 88.694 mg kg-1 ）是所有 SCG 样品中含量最高的化合物，其次是酚酸，如咖啡酸、阿魏酸，没食子酸，对香豆素，丁香，反式肉桂酸，和香草酸。此外，几乎所有样品中都含有一些黄酮类化合物，即芦丁、花青素3-葡萄糖苷和槲皮素。这项工作提供了对 SCG 中生物活性化合物的深入表征，并有助于开发新的再利用策略。