Saffloflavonesides A and B, two rearranged derivatives of flavonoid C-glycosides with a furan-tetrahydrofuran ring from Carthamus tinctorius.

Two new rearranged derivatives of flavonoid C-glycosides, saffloflavonesides A (1) and B (2), were isolated from the florets of Carthamus tinctorius. Their structures were determined using UV, IR, HRESIMS, and 1D and 2D NMR data and by comparing experimental and calculated electronic circular dichroism (ECD) spectra. Compounds 1 and 2 were unprecedented chalcone and flavanone derivatives possessing a furan conjoining tetrahydrofuran ring. A potential biosynthetic pathway was proposed. At 10 μM, 1 and 2 both showed strong inhibitory activity against PC12 cell damage induced by rotenone.