Chemical constituents of the seeds of Citrus reticulata and their bioactivity

Four new limonoids (1–4), reticulactone A (1), 21,23-dihydro-23-ethoxy-21-oxolimonin (2), tetrahydro-20,22-dihydroxy-21,23-diethoxy-nomilin (3), and dasycarinone B (4), as well as 11 known limonoids and one known carbolic acid, were isolated from the EtOH extract of the seeds of Citrus reticulata Blanco. The inhibitory effects of 15 limonoids (1–15) on the proliferation of HepG2 liver cancer cells were evaluated using the CCK-8 assay. Based on their structural characteristics, the results revealed that the typical limonoid compounds 2, 5, 10, and 12 exhibited stronger cytotoxicity compared to other limonoid compounds. Notably, the novel compound 2 demonstrated the strongest cytotoxic activity (IC50 = 18.24 ± 2.78 μM).