Determination of polyphenolic compounds in raw plant materials by NMR spectroscopy Anzhelika Sheremeta, Vasilii Vasil’ev, Vasilii Ivlev, Sergey Goriainov and Victoria Romashchenko E3S Web Conf., 555 (2024) 03010 Published online: 30 July 2024 DOI: 10.1051/e3sconf/202455503010