Table 3 Characteristic chemical shifts for flavonoids [29]
From: Flavonoids: isolation, characterization, and health benefits
Chemical shifts (ppm) | 1H |
|---|---|
2–3 | H-3 (flavanone, CH3 aromatic) |
4–6 | H-2 (dihydroflavonol, flavanone) |
6–8 | A and B ring protons |
8–8.5 | H-2 (isoflavone) |
12–14 | 5-OH when C═O at C4 (DMSO d6) |
Chemical shifts (ppm) | 13C |
28–35 | C-4 (flavanol) |
40–80 | Non-oxygenated (C-2,-C-3-flavanone/flavanol) |
90–125 (with ortho/para oxygenation) | Non-oxygenated aromatic carbons |
125–135 (para substitution) | Non-oxygenated aromatic carbons |
130–150 (with ortho/para oxygenation) | Oxygenated aromatic carbons |
155–165 (no ortho/para oxygenation) | Oxygenated aromatic carbons |
170–210 | C═O |