Two structurally distinct chalcone dimers from Helichrysum zivojinii and their activities in cancer cell lines

Chalcone dimers tomoroside A (1) and tomoroside B (2), along with eight known flavonoid glucosides were isolated from the aerial parts of Helichrysum zivojinii. Cell growth inhibition in cancer cell lines and modulation of mRNAs expression by novel chalcone dimers have been assessed. •A phytochemical study was carried out on the aerial parts of Helichrysum zivojinii.•Two dimer chalcone glucosides and eight known flavonoid glucosides were isolated.•The structures of compounds were elucidated by spectroscopic techniques.•Activities in cancer cell lines of both chalcone dimer glucosides have been assessed. Dimers tomoroside A (1) and tomoroside B (2) of the co-occuring known chalcone monomer (3), along with the seven known flavonoid glucosides (4–10), were isolated from the aerial parts of Helichrysum zivojinii Černjavski & Soška. The structures of the isolated compounds were elucidated by spectroscopic techniques. Compound 1 inhibited topo IIα and hif-1α expression and stimulated doxorubicin anticancer effect, while 2 increased the expression of hif-1α, probably acting as antioxidant and redox status modulator. Notably, 2 synergized with Tipifarnib showing potential to improve the action of this new chemotherapeutic involved in the modulation of mitogene activated protein (MAP) kinase signaling pathway.