Meroterpenoids with Antitumor Activities from Guava (Psidium guajava)

Psidium guajava L., a species native to South America, has been widely cultivated in the tropical and subtropical areas of China for its popular fruits. The preliminary analysis by liquid chromatography-ultraviolet (LC-UV) indicated the presence of meroterpenoids in the fruits of P. guajava (guava). Subsequent fractionation of the petroleum ether extract resulted in the identification of two new meroterpenoids, psiguajavadials A ( 1 ) and B ( 2 ), together with 14 previously described meroterpenoids ( 3 – 16 ). Their structures were fully elucidated by comprehensive spectroscopic techniques and theoretical calculations. All of the meroterpenoids showed cytotoxicities against five human cancer cell lines, with guajadial B ( 12 ) being the most effective having an IC 50 value of 150 nM toward A549 cells. Furthermore, biochemical topoisomerase I (Top1) assay revealed that psiguajavadial A ( 1 ), psiguajavadial B ( 2 ), guajadial B ( 12 ), guajadial C ( 14 ), and guajadial F ( 16 ) acted as Top1 catalytic inhibitors and delayed Top1 poison-mediated DNA damage. The flow cytometric analysis indicated that the new meroterpenoids psiguajavadials A ( 1 ) and B ( 2 ) could induce apoptosis of HCT116 cells. These data suggest that meroterpenoids from guava fruit could be used for the development of antitumor agents.