showing the
coupling from proton H-1″ (δH 3.46) of the geranyl group
coupled to C-2′ (δC 154.5), C-3′ (δC 117.0) and C-4′ (δC 158.8)
confirmed the geranyl group coupled to C-3′. In contrast, the
prenyl methylenic protons H-11 (δH 3.08) correlated with C-2
(δC 162.1), C-3 (δC 122.2) and C-4 (δC 183.9) indicating that the
prenyl moiety is attached to C-3. Thus 1 was newly elucidated
as 3′-geranyl-3-prenyl-2′,4′,5,7-tetrahydroxyflavone. Compounds
6 and 7 may be biosynthetized from the precursor 1
through the cyclization of the geranyl chain with the adjacent
hydroxy groups 4′-OH and 2′-OH, respectively