Determination of metabolite differences between loquat nectar and honey by UPLC-MS/MS

Honey is a widely consumed natural agricultural product. Honey bees produce honey by collecting nectar from different flowers and then metabolising it to form honey which is stored in the hive. The current focus of research has been on the primary characteristic metabolites of monofloral honey from different plant sources,. There is a lack of understanding of the differences in the transformation and composition of overall metabolites between plant nectar and the honey that is processed by bees after nectar feeding. In this study, loquat nectar and mature loquat honey were used for the detection of all non-volatile metabolites in both by Ultra Performance Liquid Chromatography-Tandem mass spectrometry (UPLC-MS/MS). Subsequently, an analysis was conducted on the primary metabolites, including saccharides, amino acids and their derivatives, nucleotides and their derivatives, lipids, and organic acids. In addition, the secondary metabolites, including flavonoids, phenolic acids, and terpenoid, were analysed. The results showed that there was a significant difference in the relative content of non-volatile metabolites between the two. We detected a total of 914 non-volatile metabolites, of which 834 were detected in loquat nectar and 759 in loquat honey. We analyzed the relative content of metabolites based on their classification and found that the relative content of primary and secondary metabolites showed different trends after processing by bees. Among them, the content of nucleotides and their derivatives and sugar metabolites in loquat honey was generally higher than that in loquat honey. This result presents a comprehensive picture of the non-volatile metabolite composition of loquat nectar and loquat honey, and systematically compares the changes in the relative content of the two substances.蜂蜜是一种广为消费的天然农产品。蜜蜂通过采集不同花朵的花蜜，经代谢转化后生成蜂蜜并储存于蜂巢中。当前研究多聚焦于不同植物来源的单花蜂蜜（monofloral honey）的核心特征代谢物，而对于植物花蜜与蜜蜂采集加工后形成的蜂蜜之间，整体代谢物的转化与组成差异仍缺乏深入认知。本研究以枇杷花蜜与成熟枇杷蜂蜜为实验材料，采用超高效液相色谱-串联质谱（Ultra Performance Liquid Chromatography-Tandem mass spectrometry，UPLC-MS/MS）对二者的全部非挥发性代谢物进行检测。随后针对初生代谢物（primary metabolites）展开分析，涵盖糖类、氨基酸及其衍生物、核苷酸及其衍生物、脂类以及有机酸等类别；同时对次生代谢物（secondary metabolites），包括类黄酮、酚酸、萜类等进行解析。研究结果显示，二者的非挥发性代谢物相对含量存在显著差异。本研究共检出914种非挥发性代谢物，其中枇杷花蜜中检出834种，枇杷蜂蜜中检出759种。基于代谢物分类对其相对含量进行分析后发现，经蜜蜂加工后，初生代谢物与次生代谢物的相对含量呈现出不同的变化趋势。其中，枇杷蜂蜜中核苷酸及其衍生物与糖类代谢物的含量普遍高于枇杷花蜜。本研究全面刻画了枇杷花蜜与成熟枇杷蜂蜜的非挥发性代谢物组成，并系统比较了二者的相对含量变化。