Fischer Annik, Keller Helen, Droste Jörn, Gök Recep, Esatbeyoglu Tuba
Department of Molecular Food Chemistry and Food Development, Institute of Food and One Health, Leibniz University Hannover, Am Kleinen Felde 30, 30167, Hannover, Germany.
Institute of Organic Chemistry, Leibniz University Hannover, Schneiderberg 1B, 30167, Hannover, Germany.
Curr Res Food Sci. 2025 Aug 9;11:101160. doi: 10.1016/j.crfs.2025.101160. eCollection 2025.
A- and B-type procyanidins (PCs) are widely known for their health-promoting properties, such as antioxidant activity. The limited availability of reference substances represents a major challenge, resulting in a low number of systematic studies on their health benefits. In our study, the optimised 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-induced oxidation of the B-types B1 and B2 was carried out yielding the corresponding A-types A1 (1) and A2 (2), which have an additional ether bridge between C2--C7, whereas oxidation of B3 and B4 produced a six-membered spirocyclic ring system including a spiro-carbon atom at C8t (3-5). The compounds (1-5) were fully characterised by combining circular dichroism (CD) and low-temperature NMR spectroscopy at 253.0 K in acetone- including one-dimensional (1D; H and C NMR) and two-dimensional (2D; H-H COSY, H-H TOCSY, H-C HSQC, H-C HMBC, H-H ROESY) NMR experiments. The collision cross section (CCS) values from the trapped ion mobility spectrometry (TIMS) and time of flight mass spectrometry analysis (TOF-MS) allowed a rapid differentiation of the dimeric A-types, C4→C8-linked B-types, and spiro-linked PCs in combination with their retention times. A comparative analysis of the antioxidant properties of the A-, B-types, and spiro-linked PCs was conducted for the first time. The spiro-linked PCs (3-5) were found to have an equal or even higher antioxidant activity compared to the A-types A1 (1) and A2 (2) and the comparative analysis of the different procyanidin types revealed new insights into their antioxidant properties.
A 型和 B 型原花青素（PCs）因其促进健康的特性而广为人知，比如抗氧化活性。参考物质的可获得性有限是一个重大挑战，导致对其健康益处的系统性研究数量较少。在我们的研究中，对 B 型的 B1 和 B2 进行了优化的 2,2-二苯基-1-苦基肼自由基（DPPH）诱导氧化，生成了相应的 A 型 A1（1）和 A2（2），它们在 C2-C7 之间有一个额外的醚桥，而 B3 和 B4 的氧化产生了一个六元螺环系统，在 C8t 处有一个螺碳原子（3-5）。通过在 253.0 K 的丙酮中结合圆二色性（CD）和低温核磁共振光谱对化合物（1-5）进行了全面表征，包括一维（1D；氢和碳核磁共振）和二维（2D；氢-氢化学位移相关谱、氢-氢全相关谱、氢-碳异核单量子相干谱、氢-碳异核多键相关谱、氢-氢旋转框架 Overhauser 效应谱）核磁共振实验。捕集离子淌度质谱（TIMS）和飞行时间质谱分析（TOF-MS）得到的碰撞截面（CCS）值，结合它们的保留时间，能够快速区分二聚体 A 型、C4→C8 连接的 B 型和螺环连接的原花青素。首次对 A 型、B 型和螺环连接的原花青素的抗氧化性能进行了比较分析。发现螺环连接的原花青素（3-5）与 A 型 A1（1）和 A2（2）相比具有同等甚至更高的抗氧化活性，对不同原花青素类型的比较分析揭示了它们抗氧化性能的新见解。
