Toonamonoids A and B: two new limonoids from Toona ciliata var. yunnanensis (C.DC.) C.Y.Wu and their cytotoxic activity

Two previously undescribed limonoids, designated as toonamonoids A and B (1–2), featuring a rare γ-crotonolactone motif at C-17 instead of the typical furan ring, were isolated from Toona ciliata. var. yunnanensis (C.DC.) C.Y.Wu. Along with these, three known analogues (3–5) were also identified. The compounds were extracted using ethyl acetate (EtOAc) from the plant’s twigs and leaves. Structural elucidation, including determination of absolute stereochemistry, was accomplished through comprehensive spectroscopic analysis involving 1D and 2D NMR techniques, complemented by high-resolution mass spectrometry (HRMS). In vitro cytotoxicity was assessed against two human cancer cell lines. However, none of the isolated compounds (IC50 values >10 μM) demonstrated notable cytotoxic activity when compared to the cisplatin.