Typically NMR data of polyphenols is the last piece of information that is needed to verify their structures
NMR is the ultimate tool for polyphenol identification, but since it is quite insensitive, it cannot be used for the routine structural analysis of all the phenolics one detects in plants. For this reason other phytochemical tools are typically used first and NMR is preserved for those compounds that are new to the phytochemist and need to be thus fully identified. It is clear that NMR is one of the only methods that can unequivocally characterize the whole polyphenol structure, including e.g. positions of various functional groups that would be difficult or even impossible to conclude from MS or MS/MS data.