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).