NMR Chemical Shifts of Common Flavonoids.

We present 1H and 13C nuclear magnetic resonance (NMR) chemical shifts for the most common flavonoids, a class of natural products widely present in the plant kingdom. Our data are acquired in three common NMR solvents: methanol d4, dimethyl sulfoxide d6, and pyridine d5 and may be used as a reference for isolated compounds, for detecting flavonoids within mixtures like plant extracts as shown in an example, as reference data for natural product databases, for refined training of prediction software, and for machine learning in resonance assignment and NMR-based structure elucidation. Solvent- and substitution-induced resonance shifts are discussed.