Limonoids From Cultivated Citrus × Sphaerocarpa Y. Nakaj. ex H. Ohba

Background The chemical constituents of Citrus × sphaerocarpa Y. Nakaj. ex H. Ohba, a cultivated Citrus species, remain insufficiently characterized despite its agricultural relevance. To expand knowledge of bioactive metabolites in Citrus plants, a methanol extract of C. × sphaerocarpa peels was investigated. Methods The methanol extract from C. × sphaerocarpa peels was repeatedly separated and purified, and the structures of the isolated compounds were elucidated using nuclear magnetic resonance and mass spectrometry analyses. The anti-proliferative activities of the isolated compounds were assessed using the WST-8 assay. Results A novel limonoid derivative, 21,23-dihydro-21-oxodeacetylnomilin, was isolated from the peels, along with two known limonoids, limonexic acid and shihulimonin A. None of the compounds showed significant anti-proliferative activity against human glioblastoma cell lines T98G and U-251 MG. Conclusions This study provides the first detailed characterization of limonoids from C. × sphaerocarpa , contributing to a deeper chemotaxonomic understanding of this cultivated Citrus species.