In this research work grape stalk samples from the Douro region were analyzed concerning polyphenolic composition. Different solid–liquid extraction conditions were tested for reaching the optimal parameters to obtain higher amounts of polyphenols. In general, the best conditions comprise the use of a mixture of acetone/ethanol/water (1:1:1) at room temperature during 20 min, using a pre-wash treatment with deionized water. The polyphenolic extractions with acetone are generally more effective than without acetone.

Total phenolic determination (Folin-Ciocalteu), antioxidant capacity (DPPH/FRAP) and more accurate methods such as HPLC-DAD and HPLC-ESI-MS were performed. An intensive polyphenolic characterization (including a possible identification of a new polyphenol) and compound quantification was achieved. A comparative study between these two analysis approaches was accomplished, which allowed to conclude that the Folin-Ciocalteu and DPPH/FRAP determinations do not always allow a direct correspondence between high phenolic content or antioxidant/reducing capacity and real high polyphenolic content on crude polyphenolic extracts.

在这项研究工作中，对杜罗地区的葡萄秸秆样品进行了多酚成分分析。测试了不同的固液萃取条件，以达到最佳参数以获得更高含量的多酚。通常，最佳条件包括在室温下20分钟内使用丙酮/乙醇/水（1：1：1）的混合物，并用去离子水进行预洗处理。用丙酮进行多酚提取通常比不使用丙酮更有效。

进行了总酚测定（Folin-Ciocalteu），抗氧化能力（DPPH / FRAP）和更准确的方法，如HPLC-DAD和HPLC-ESI-MS。进行了深入的多酚表征（包括可能的新多酚鉴定）和化合物定量。对这两种分析方法进行了比较研究，得出的结论是，Folin-Ciocalteu和DPPH / FRAP的测定并不总能使粗制多酚提取物中的高酚含量或抗氧化剂/还原能力与实际高多酚含量直接对应。