The current investigation aims to optimize the extraction of leaf phenolics of Centaurea sp. and to propose a scientific basis for an optimal collection of this plant. Centaurea sp. samples were collected regularly over seven months from January to July 2017 (the non-estivation period). They were then subjected to preliminary ultrasound-assisted extraction (UAE) assays employing four solvents at different polarity (methanol, ethanol, ethyl-acetate, and acetone). April samples extracted in methanol, which revealed maximum recovery of phenolic content, were selected for UAE optimization employing the Box–Behnken design (BBD) technique under the category of the response surface methodology (RSM). In this step, three parameters including time X₁ (min), temperature X₂ (°C) and sample-to-solvent ratio X₃ (g/mL) were used to maximize three responses including total phenolic compounds (TPC) content and two different antioxidant capacity assays, DPPH and FRAP. The results under the optimum conditions were significant: TPC 46.44 “mg GAE/g dm”, DPPH 38.91 “mg AAEAC/g dm”, and FRAP 41.71 “mg AAEAC/g dm”. Moreover, 14 phenolic acids were detected and quantified under optimum conditions after running high-performance liquid chromatography analysis (HPLC-DAD). Protocatechuic acid was found at the highest concentration (564.62 ± 0.44 μg/g dm) followed by p-coumaric acid (277.89 ± 0.90 μg/g dm) and ferulic acid (121.52 ± 3.83 μg/g dm). On the other hand, both predicted and experimental BBD responses were in accordance, which points the success of the optimization.

目前的调查旨在优化Centaurea sp.叶酚类物质的提取。并为该植物的最佳收集提出科学依据。Centaurea sp. 样本是在 2017 年 1 月至 7 月（非采摘期）的七个月内定期收集的。然后使用四种不同极性的溶剂（甲醇、乙醇、乙酸乙酯和丙酮）对它们进行初步超声辅助提取 (UAE) 分析。在响应面方法 (RSM) 类别下，采用 Box-Behnken 设计 (BBD) 技术选择了在甲醇中提取的 4 月样品进行了阿联酋优化，该样品显示酚类含量的回收率最高。在这一步中，三个参数包括时间 X ₁(min)、温度 X ₂ (°C) 和样品溶剂比 X ₃ (g/mL) 用于最大化三种响应，包括总酚类化合物 (TPC) 含量和两种不同的抗氧化能力测定，DPPH 和 FRAP。最佳条件下的结果显着：TPC 46.44“mg GAE/g dm”、DPPH 38.91“mg AAEAC/g dm”和FRAP 41.71“mg AAEAC/g dm”。此外，在运行高效液相色谱分析 (HPLC-DAD) 后，在最佳条件下检测并定量了 14 种酚酸。原儿茶酸浓度最高 (564.62 ± 0.44 μg/g dm)，其次是p-香豆酸 (277.89 ± 0.90 μg/g dm) 和阿魏酸 (121.52 ± 3.83 μg/g dm)。另一方面，预测的和实验的 BBD 响应是一致的，这表明优化的成功。