2.1. Chemicals and Reagents

Most of the chemicals used for extraction and characterization were analytical grade and purchased from Sigma-Aldrich (Castle Hill, NSW, Australia). The standards for antioxidant assays included gallic acid, quercetin, catechin and L-ascorbic acid, which were purchased from Sigma-Aldrich (St. Louis, MO, USA). For antioxidant assays, Folin and Ciocalteu’s phenol, aluminium chloride hexahydrate, vanillin, 2,2-diphenyl-1-picrylhydrazyl (DPPH), ferric (III) chloride anhydrous, 2,4,6-tripyridyl-s-triazine (TPTZ), potassium persulfate and 2,2′-azino-bis(3-ethylbenz-thiazoline-6-sulphonate) (ABTS) were purchased from Sigma-Aldrich (St. Louis, MO, USA) and sodium carbonate anhydrous (chem-supply; Gillman, SA, Australia), sodium acetate hydrated (Ajax Finechem, Scoreby, VIC, Australia) and sulfuric acid 98% were purchased from RCI Labscan Limited, (Bangkok, Thailand). The HPLC grade methanol was purchased from Fisher Chemical Company (San Jose, CA, USA). The mobile phases for LC-ESI-QTOF/MS and HPLC were mainly comprised of 50% acetic acid solution (Sigma-Aldrich, St. Louis, MO, USA) and acetonitrile (LiChrosolv, Darmstadt, Germany). The reference standards including protocatechuic acid, catechin, 4-hydroxybenzoic acid, chlorogenic acid, quercetin 3-O-glucoside, kaempferol 3-O-glucoside and quercetin were purchased from Sigma-Aldrich (St. Louis, MO, USA).