Sesquiterpenoids from Tithonia diversifolia (Hemsl.) A. Gray induce apoptosis and inhibit the cell cycle progression of acute myeloid leukemia cells.

Three sesquiterpene lactones (1-3) were isolated from the aerial part of Tithonia diversifolia (Hemsl.) A. Gray grown in the Hoa Binh province in Viet Nam. The structures of these three sesquiterpene lactones were identified as tagitinin A (1), 1β-hydroxytirotundin 3-O-methyl ether (2), and tagitinin C (3) by analyzing spectroscopic data. For the first time, compound 2 was isolated from T. diversifolia growing in Viet Nam. Furthermore, contrary to existing literature, we determined that compound 1 was the major isolate. Compounds 1 and 3 significantly decreased numbers of acute myeloid leukemia OCI-AML3 cells by promoting apoptosis and causing cell cycle arrest at G0/G1 phase at concentrations as low as 2.5 μg/mL (compound 1) and 0.25 μg/mL (compound 3). Additionally, all three compounds showed cytotoxic activity against five human cancer cell lines (A549, T24, Huh-7, 8505, and SNU-1), with IC₅₀ values ranging from 1.32 ± 0.14 to 46.34 ± 2.74 μM. Overall, our findings suggest that compounds 1 and 3 may be potential anti-cancer therapeutics and thus warrant further study.