Limonin is a bitter triterpenoid dilactone in the genus Citrus with potential medicinal value. In this study, the metabolism of limonin in human was characterized by high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (HPLC-Q-TOF-MS). A total of 7 metabolites were identified from human samples. Among them, 3 metabolites of M1, M2 and M4 were detected in urine and feces, and the others were found in intestinal bacteria sample. Notably, M1 and M3 were chemically synthesized, of which the structures were further confirmed by NMR spectra data. The metabolism of limonin involved three major pathways, namely, reduction, hydrolysis and methylation. The reduction and hydrolysis were commonly observed in ring D of limonin. The metabolites showed decomposition in ring A. This study provides data for the metabolism of limonin in humans, and will contribute to explain its biological activity.

柠檬苦素是柑橘属苦三萜类双内酯具有潜在的药用价值。在这项研究中，柠檬苦素在人体内的代谢通过高效液相色谱/四极杆飞行时间质谱（HPLC-Q-TOF-MS）进行表征。从人类样品中总共鉴定出7种代谢物。其中，在尿液和粪便中检测到3种M1，M2和M4代谢物，在肠道细菌样品中发现了其他代谢物。值得注意的是，M1和M3是化学合成的，其结构通过NMR光谱数据进一步证实。柠檬苦素的代谢涉及三个主要途径，即还原，水解和甲基化。还原和水解通常在柠檬苦素的D环中观察到。代谢物在A环上显示分解。这项研究提供了柠檬苦素在人体中的代谢数据，