Homogentisic

Acetonitrile 99.9%, n-hexane 95% and methanol 99.9% were purchased from Fisher Scientific (Shanghai, China). The fatty acids methyl ester (FAME) reference standard mixture 37 (standard 47885-U) was purchased from Sigma (St. Louis, MO, USA). Sugars standards [glucose, sorbitol and d(+)-trehalose and myo-inositol], phenolic standards (gallic, 4-hydroxybenzoic, 3,4-dihydroxybenzaldehyde, homogentisic, p-coumaric and o-coumaric acids) were purchased from Sigma (St. Louis, MO, USA) or Sigma-Aldrich Chem (shanghai, China). 1,1-Diphenyl-2-picryl-hydrazyl (DPPH), BHT, 3-(2-pyridyl)-5,6-bis (4-phenyl-sulfonic acid)-1,2,4-triazine (ferrozine), rutin and ascorbic acid were purchased from Sigma Chemical Co. BSTFA + TMCS (99:1) was purchased from Supelco. Folin–Ciocalteu’s phenol reagent was purchased from Beijing Solarbio reagent company (Beijing, China). Ferrous chloride, sodium salicylate, ferrous sulphate, hydrogen peroxide, potassium ferricyanide, trichloroacetic acid, disodium phosphate, sodium dihydrogen phosphate, ferric chloride, sodium carbonate, sodium hydroxide, aluminium nitrate, sodium nitrite, petroleum ether (60–90 °C), ethanol and methanol were all purchased from Beijing chemical plant (Beijing, China). All chemicals were of analytical grade. Water was treated in a Milli-Q water purification system (TGI Pure Water Systems, USA).

Analytical standards (all with purity ≥ 95%) of caffeic, 5-O-caffeoylqunic, gallic, ferulic, isoferulic, homoGentisic, protocatechuic, 3-hydroxybenzoic, 4-hydroxybenzoic, rosmarinic, 3,4-dihydroxyphenylacetic, vanillic, syringic, m-coumaric, o-coumaric, p-coumaric, salicylic, 3,4-dimethoxycinnamic, α-resorcylic, β-resorcylic, γ-resorcylic, 3,5-dimethoxybenzoic acid, 3-O-methylquercetin, chrysin, isorhamnetin, kaempferol, luteolin, morin, prunetin, rhamnetin, sakuranetin, taxifolin, and LC grade acetonitrile, methanol were purchased from Sigma-Aldrich Fine Chemicals (St. Louis, MO, USA). Gentisic, sinapic, veratric acids, eriodictyol, myricetin and rhamnazin were from ChromaDex (Irvine, USA). Apigenin and naringenin were from Roth (Karlsruhe, Germany) and quercetin was from Fluka (Buchs, Switzerland). LC grade water was prepared using a Millipore Direct-Q3 purification system (Bedford, MA, USA).