New Use Agriculture and Natural Plant Products Program, Department of Plant Biology, Rutgers University, 59 Dudley Road, New Brunswick, NJ 08901, USA.
Department of Food Science, Rutgers University, 65 Dudley Road, New Brunswick, NJ 08901, USA.
J Food Drug Anal. 2019 Jul;27(3):778-785. doi: 10.1016/j.jfda.2018.07.005. Epub 2018 Aug 14.
Raspberry ketone (RK) is the characteristic aromatic compound in raspberry (Rubus idaeus L.) with wide applications as food additive and anti-obesity agent. However, quantification of RK has presented difficulties in MS detection and reliable LC-MS method for RK analysis in literature is in limit to date. In order to facilitate quality control of raspberry derived products and RK metabolomics study, this study aimed to develop a validated and sensitive UHPLC-MS/MS method. Strong in-source fragmentation was noted and the fragmental ion of 107 m/z produced was selected as the precursor ion for MRM detection, and as such the electrospray ionization performance was optimized by fractional factorial design to accommodate such ion-source dissociation behavior as well as its moderate volatility. A pathway involving the formation of quinone-like structure with strong conjugation was proposed to explain the intense in-source fragmentation. The MRM transition was optimized with product ion of 77 m/z selected as the quantifier ion. The method featured low limit of quantification of ∼2 ng/mL and allowed for rapid detection of RK in fresh raspberries following direct sample preparation. RK contents were found to be higher from locally grown and harvested farm sources compared to commercial products shipped into the state, and higher in those at late-stage compared with early-stage maturity. No correlations in RK content between organic and non-organic labels were noted.
覆盆子酮（RK）是覆盆子（Rubus idaeus L.）中特有的芳香化合物，作为食品添加剂和抗肥胖剂具有广泛的应用。然而，在 MS 检测中，RK 的定量存在困难，并且迄今为止，文献中可靠的 LC-MS 方法分析 RK 的应用也有限。为了便于控制覆盆子衍生产品的质量和 RK 代谢组学研究，本研究旨在开发一种经过验证和灵敏的 UHPLC-MS/MS 方法。研究中注意到强烈的源内碎裂，选择 107 m/z 的碎片离子作为 MRM 检测的前体离子，并采用部分因子设计优化电喷雾电离性能，以适应这种离子源解离行为及其中等挥发性。提出了一种涉及形成具有强共轭的醌样结构的途径来解释强烈的源内碎裂。选择 77 m/z 的产物离子作为定量离子对 MRM 转换进行了优化。该方法的定量下限低至约 2ng/mL，允许在直接样品制备后快速检测新鲜覆盆子中的 RK。与商业产品相比，本地种植和收获的农场来源的 RK 含量更高，与早期成熟相比，晚期成熟的 RK 含量更高。有机和非有机标签之间的 RK 含量没有相关性。
