acid (pHBA), m-hydroxybenzoic acid
(mHBA), 3,4-dihydroxybenzoic acid (PCA, protocathecuic acid), vanillic
acid (VA), syringic acid (SyA), p-coumaric acid (CuA),
caffeic acid (CA), ferulic acid (FA), sinapic acid (SA), 5-caffeoylquinic
acid (CQA), quercetin (Q), kampferol (K), rutin (Ru), 3-(trimethylsilyl)propionic-2,2,3,3-d4 acid sodium salt (TSP), sodium azide, deuterium
oxide, and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical were of analytical
grade, acquired from Sigma-Aldrich (Milano, Italy) and used as received.
The Folin-Ciocalteu phenol reagent was purchased from Sinopharm Chemical
Reagent (Shanghai, China). HPLC grade acetonitrile and methanol were
purchased from Carlo Erba (Milano, Italy); HPLC grade water was prepared
with the Milli-Q purification system (Millipore, Vimodrone, Italy).