Protocatechuic acid

Standard compounds including gallic acid, protocatechuic acid, catechol, chlorogenic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, sinapic acid, syringic acid, vanillin, ferulic acid, p-coumaric acid, benzoic acid, ellagic acid, cinnamic acid, apigenin, (+)-catechin, esculetin, fisetin, galangin, isohamnetin, isoquercitrin, kaempferol, luteolin, myricetin, quercetin, rhamnetin, and rutin, were purchased from Kanto Chemical Co., Inc., Tokyo, Japan.
Reagents including 1,1-diphenyl-2-picrylhydrazyl (DPPH), dibutyl hydroxytoluene (BHT), 2,2′-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS), potassium persulfate (K₂S₂O₈), Folin-Ciocalteu’s reagent, aluminium (III) chloride hexahydrate (AlCl₃·6H₂O), β-carotene, linoleic acid, polyoxyethylen esorbitan monopalmitate (Tween-40), trichloroacetic acid (CCl₃COOH), iron (III) chloride (FeCl₃), sodium carbonate (Na₂CO₃), disodium hydrogenphosphate (Na₂HPO₄), sodium dihydrogenphosphate (NaH₂PO₄), sodium hydroxide (NaOH), and hydrochloric acid (HCl), were obtained from Kanto Chemical Co., Inc., Tokyo, Japan. All chemicals used were of analytical grade.

The standard compounds for validating the phenolic compounds, including gallic acid, protocatechuic acid, catechol, chlorogenic acid, p-hydroxybenzoic acid, vanillic acid, caffeic acid, syringic acid, vanillin, ferulic acid, sinapic acid, p-coumaric acid, benzoic acid, ellagic acid, and cinnamic acid, were purchased from Kanto Chemical Co., Inc., Tokyo, Japan.